- Add cpufreq pressure feedback for the scheduler
- Rework misfit load-balancing wrt. affinity restrictions
- Clean up and simplify the code around ::overutilized and
::overload access.
- Simplify sched_balance_newidle()
- Bump SCHEDSTAT_VERSION to 16 due to a cleanup of CPU_MAX_IDLE_TYPES
handling that changed the output.
- Rework & clean up <asm/vtime.h> interactions wrt. arch_vtime_task_switch()
- Reorganize, clean up and unify most of the higher level
scheduler balancing function names around the sched_balance_*()
prefix.
- Simplify the balancing flag code (sched_balance_running)
- Miscellaneous cleanups & fixes
Signed-off-by: Ingo Molnar <mingo@kernel.org>
-----BEGIN PGP SIGNATURE-----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=obph
-----END PGP SIGNATURE-----
Merge tag 'sched-core-2024-05-13' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull scheduler updates from Ingo Molnar:
- Add cpufreq pressure feedback for the scheduler
- Rework misfit load-balancing wrt affinity restrictions
- Clean up and simplify the code around ::overutilized and
::overload access.
- Simplify sched_balance_newidle()
- Bump SCHEDSTAT_VERSION to 16 due to a cleanup of CPU_MAX_IDLE_TYPES
handling that changed the output.
- Rework & clean up <asm/vtime.h> interactions wrt arch_vtime_task_switch()
- Reorganize, clean up and unify most of the higher level
scheduler balancing function names around the sched_balance_*()
prefix
- Simplify the balancing flag code (sched_balance_running)
- Miscellaneous cleanups & fixes
* tag 'sched-core-2024-05-13' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (50 commits)
sched/pelt: Remove shift of thermal clock
sched/cpufreq: Rename arch_update_thermal_pressure() => arch_update_hw_pressure()
thermal/cpufreq: Remove arch_update_thermal_pressure()
sched/cpufreq: Take cpufreq feedback into account
cpufreq: Add a cpufreq pressure feedback for the scheduler
sched/fair: Fix update of rd->sg_overutilized
sched/vtime: Do not include <asm/vtime.h> header
s390/irq,nmi: Include <asm/vtime.h> header directly
s390/vtime: Remove unused __ARCH_HAS_VTIME_TASK_SWITCH leftover
sched/vtime: Get rid of generic vtime_task_switch() implementation
sched/vtime: Remove confusing arch_vtime_task_switch() declaration
sched/balancing: Simplify the sg_status bitmask and use separate ->overloaded and ->overutilized flags
sched/fair: Rename set_rd_overutilized_status() to set_rd_overutilized()
sched/fair: Rename SG_OVERLOAD to SG_OVERLOADED
sched/fair: Rename {set|get}_rd_overload() to {set|get}_rd_overloaded()
sched/fair: Rename root_domain::overload to ::overloaded
sched/fair: Use helper functions to access root_domain::overload
sched/fair: Check root_domain::overload value before update
sched/fair: Combine EAS check with root_domain::overutilized access
sched/fair: Simplify the continue_balancing logic in sched_balance_newidle()
...
The default nna (node_nr_active) is used when the pool isn't tied to a
specific NUMA node. This can happen in the following cases:
1. On NUMA, if per-node pwq init failure and the fallback pwq is used.
2. On NUMA, if a pool is configured to span multiple nodes.
3. On single node setups.
5797b1c189 ("workqueue: Implement system-wide nr_active enforcement for
unbound workqueues") set the default nna->max to min_active because only #1
was being considered. For #2 and #3, using min_active means that the max
concurrency in normal operation is pushed down to min_active which is
currently 8, which can obviously lead to performance issues.
exact value nna->max is set to doesn't really matter. #2 can only happen if
the workqueue is intentionally configured to ignore NUMA boundaries and
there's no good way to distribute max_active in this case. #3 is the default
behavior on single node machines.
Let's set it the default nna->max to max_active. This fixes the artificially
lowered concurrency problem on single node machines and shouldn't hurt
anything for other cases.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-by: Shinichiro Kawasaki <shinichiro.kawasaki@wdc.com>
Fixes: 5797b1c189 ("workqueue: Implement system-wide nr_active enforcement for unbound workqueues")
Link: https://lore.kernel.org/dm-devel/20240410084531.2134621-1-shinichiro.kawasaki@wdc.com/
Signed-off-by: Tejun Heo <tj@kernel.org>
With cpu_possible_mask=0-63 and cpu_online_mask=0-7 the following
kernel oops was observed:
smp: Bringing up secondary CPUs ...
smp: Brought up 1 node, 8 CPUs
Unable to handle kernel pointer dereference in virtual kernel address space
Failing address: 0000000000000000 TEID: 0000000000000803
[..]
Call Trace:
arch_vcpu_is_preempted+0x12/0x80
select_idle_sibling+0x42/0x560
select_task_rq_fair+0x29a/0x3b0
try_to_wake_up+0x38e/0x6e0
kick_pool+0xa4/0x198
__queue_work.part.0+0x2bc/0x3a8
call_timer_fn+0x36/0x160
__run_timers+0x1e2/0x328
__run_timer_base+0x5a/0x88
run_timer_softirq+0x40/0x78
__do_softirq+0x118/0x388
irq_exit_rcu+0xc0/0xd8
do_ext_irq+0xae/0x168
ext_int_handler+0xbe/0xf0
psw_idle_exit+0x0/0xc
default_idle_call+0x3c/0x110
do_idle+0xd4/0x158
cpu_startup_entry+0x40/0x48
rest_init+0xc6/0xc8
start_kernel+0x3c4/0x5e0
startup_continue+0x3c/0x50
The crash is caused by calling arch_vcpu_is_preempted() for an offline
CPU. To avoid this, select the cpu with cpumask_any_and_distribute()
to mask __pod_cpumask with cpu_online_mask. In case no cpu is left in
the pool, skip the assignment.
tj: This doesn't fully fix the bug as CPUs can still go down between picking
the target CPU and the wake call. Fixing that likely requires adding
cpu_online() test to either the sched or s390 arch code. However, regardless
of how that is fixed, workqueue shouldn't be picking a CPU which isn't
online as that would result in unpredictable and worse behavior.
Signed-off-by: Sven Schnelle <svens@linux.ibm.com>
Fixes: 8639ecebc9 ("workqueue: Implement non-strict affinity scope for unbound workqueues")
Cc: stable@vger.kernel.org # v6.6+
Signed-off-by: Tejun Heo <tj@kernel.org>
While reviewing users of subsys_virtual_register() I noticed that
wq_sysfs_init() ignores the @groups argument. This looks like a
historical artifact as the original wq_subsys only had one attribute to
register.
On the way to building up an @groups argument to pass to
subsys_virtual_register() a few more cleanups fell out:
* Use DEVICE_ATTR_RO() and DEVICE_ATTR_RW() for
cpumask_{isolated,requested} and cpumask respectively. Rename the
@show and @store methods accordingly.
* Co-locate the attribute definition with the methods. This required
moving wq_unbound_cpumask_show down next to wq_unbound_cpumask_store
(renamed to cpumask_show() and cpumask_store())
* Use ATTRIBUTE_GROUPS() to skip some boilerplate declarations
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Reviewed-by: Lai Jiangshan <jiangshanlai@gmail.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Allow more pools can be shared when attrs->affn_strict.
Signed-off-by: Lai Jiangshan <jiangshan.ljs@antgroup.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Now that work_grab_pending() can always grab the PENDING bit without
sleeping, the only thing that prevents allowing cancel_work_sync() of a BH
work item from an atomic context is the flushing of the in-flight instance.
When we're flushing a BH work item for cancel_work_sync(), we know that the
work item is not queued and must be executing in a BH context, which means
that it's safe to busy-wait for its completion from a non-hardirq atomic
context.
This patch updates __flush_work() so that it busy-waits when flushing a BH
work item for cancel_work_sync(). might_sleep() is pushed from
start_flush_work() to its callers - when operating on a BH work item,
__cancel_work_sync() now enforces !in_hardirq() instead of might_sleep().
This allows cancel_work_sync() and disable_work() to be called from
non-hardirq atomic contexts on BH work items.
v3: In __flush_work(), test WORK_OFFQ_BH to tell whether a work item being
canceled can be busy waited instead of making start_flush_work() return
the pool. (Lai)
v2: Lai pointed out that __flush_work() was accessing pool->flags outside
the RCU critical section protecting the pool pointer. Fix it by testing
and remembering the result inside the RCU critical section.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Lai Jiangshan <jiangshanlai@gmail.com>
Add an off-queue flag, WORK_OFFQ_BH, that indicates whether the last
workqueue the work item was on was a BH one. This will be used to test
whether a work item is BH in cancel_sync path to implement atomic
cancel_sync'ing for BH work items.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Lai Jiangshan <jiangshanlai@gmail.com>
cancel[_delayed]_work_sync() guarantees that it can shut down
self-requeueing work items. To achieve that, it grabs and then holds
WORK_STRUCT_PENDING bit set while flushing the currently executing instance.
As the PENDING bit is set, all queueing attempts including the
self-requeueing ones fail and once the currently executing instance is
flushed, the work item should be idle as long as someone else isn't actively
queueing it.
This means that the cancel_work_sync path may hold the PENDING bit set while
flushing the target work item. This isn't a problem for the queueing path -
it can just fail which is the desired effect. It doesn't affect flush. It
doesn't matter to cancel_work either as it can just report that the work
item has successfully canceled. However, if there's another cancel_work_sync
attempt on the work item, it can't simply fail or report success and that
would breach the guarantee that it should provide. cancel_work_sync has to
wait for and grab that PENDING bit and go through the motions.
WORK_OFFQ_CANCELING and wq_cancel_waitq are what implement this
cancel_work_sync to cancel_work_sync wait mechanism. When a work item is
being canceled, WORK_OFFQ_CANCELING is also set on it and other
cancel_work_sync attempts wait on the bit to be cleared using the wait
queue.
While this works, it's an isolated wart which doesn't jive with the rest of
flush and cancel mechanisms and forces enable_work() and disable_work() to
require a sleepable context, which hampers their usability.
Now that a work item can be disabled, we can use that to block queueing
while cancel_work_sync is in progress. Instead of holding PENDING the bit,
it can temporarily disable the work item, flush and then re-enable it as
that'd achieve the same end result of blocking queueings while canceling and
thus enable canceling of self-requeueing work items.
- WORK_OFFQ_CANCELING and the surrounding mechanims are removed.
- work_grab_pending() is now simpler, no longer has to wait for a blocking
operation and thus can be called from any context.
- With work_grab_pending() simplified, no need to use try_to_grab_pending()
directly. All users are converted to use work_grab_pending().
- __cancel_work_sync() is updated to __cancel_work() with
WORK_CANCEL_DISABLE to cancel and plug racing queueing attempts. It then
flushes and re-enables the work item if necessary.
- These changes allow disable_work() and enable_work() to be called from any
context.
v2: Lai pointed out that mod_delayed_work_on() needs to check the disable
count before queueing the delayed work item. Added
clear_pending_if_disabled() call.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Lai Jiangshan <jiangshanlai@gmail.com>
While (delayed) work items could be flushed and canceled, there was no way
to prevent them from being queued in the future. While this didn't lead to
functional deficiencies, it sometimes required a bit more effort from the
workqueue users to e.g. sequence shutdown steps with more care.
Workqueue is currently in the process of replacing tasklet which does
support disabling and enabling. The feature is used relatively widely to,
for example, temporarily suppress main path while a control plane operation
(reset or config change) is in progress.
To enable easy conversion of tasklet users and as it seems like an inherent
useful feature, this patch implements disabling and enabling of work items.
- A work item carries 16bit disable count in work->data while not queued.
The access to the count is synchronized by the PENDING bit like all other
parts of work->data.
- If the count is non-zero, the work item cannot be queued. Any attempt to
queue the work item fails and returns %false.
- disable_work[_sync](), enable_work(), disable_delayed_work[_sync]() and
enable_delayed_work() are added.
v3: enable_work() was using local_irq_enable() instead of
local_irq_restore() to undo IRQ-disable by work_grab_pending(). This is
awkward now and will become incorrect as enable_work() will later be
used from IRQ context too. (Lai)
v2: Lai noticed that queue_work_node() wasn't checking the disable count.
Fixed. queue_rcu_work() is updated to trigger warning if the inner work
item is disabled.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Lai Jiangshan <jiangshanlai@gmail.com>
The cancel[_sync] paths acquire and release WORK_STRUCT_PENDING, and
manipulate WORK_OFFQ_CANCELING. However, they assume that all the OFFQ bit
values except for the pool ID are statically known and don't preserve them,
which is not wrong in the current code as the pool ID and CANCELING are the
only information carried. However, the planned disable/enable support will
add more fields and need them to be preserved.
This patch updates work data handling so that only the bits which need
updating are updated.
- struct work_offq_data is added along with work_offqd_unpack() and
work_offqd_pack_flags() to help manipulating multiple fields contained in
work->data. Note that the helpers look a bit silly right now as there
isn't that much to pack. The next patch will add more.
- mark_work_canceling() which is used only by __cancel_work_sync() is
replaced by open-coded usage of work_offq_data and
set_work_pool_and_keep_pending() in __cancel_work_sync().
- __cancel_work[_sync]() uses offq_data helpers to preserve other OFFQ bits
when clearing WORK_STRUCT_PENDING and WORK_OFFQ_CANCELING at the end.
- This removes all users of get_work_pool_id() which is dropped. Note that
get_work_pool_id() could handle both WORK_STRUCT_PWQ and !WORK_STRUCT_PWQ
cases; however, it was only being called after try_to_grab_pending()
succeeded, in which case WORK_STRUCT_PWQ is never set and thus it's safe
to use work_offqd_unpack() instead.
No behavior changes intended.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Lai Jiangshan <jiangshanlai@gmail.com>
-----BEGIN PGP SIGNATURE-----
iQFSBAABCAA8FiEEq68RxlopcLEwq+PEeb4+QwBBGIYFAmYAlq0eHHRvcnZhbGRz
QGxpbnV4LWZvdW5kYXRpb24ub3JnAAoJEHm+PkMAQRiGYqwH/0fb4pRbVtULpiIK
Cs7/e/IWzRRWLBq+Jj2KVVTxwjyiKFNOq6K/CHHnljIWo1yN2CIWeOgbHfTI0WfN
xmBdJP7OtK8MCN9PwwoWhZxMLcyv4pFCERrrkGa7AD+cdN4j/ytQ3mH5V8f/21fd
rnpQSdpgGXB2SSMHd520Y+e56+gxrrTmsDXjZWM08Wt0bbqAWJrjNe58BMz5hI1t
yQtcgYRTdUuZBn5TMkT99lK9EFQslV38YCo7RUP5D0DWXS1jSfWlgnCD1Nc1ziF4
ps/xPdUMDJAc5Tslg/hgJOciSuLqgMzIUsVgZrKysuu3NhwDY1LDWGORmH1t8E8W
RC25950=
=F+01
-----END PGP SIGNATURE-----
Merge tag 'v6.9-rc1' into sched/core, to pick up fixes and to refresh the branch
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Here is the "big" set of driver core and kernfs changes for 6.9-rc1.
Nothing all that crazy here, just some good updates that include:
- automatic attribute group hiding from Dan Williams (he fixed up my
horrible attempt at doing this.)
- kobject lock contention fixes from Eric Dumazet
- driver core cleanups from Andy
- kernfs rcu work from Tejun
- fw_devlink changes to resolve some reported issues
- other minor changes, all details in the shortlog
All of these have been in linux-next for a long time with no reported
issues.
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-----BEGIN PGP SIGNATURE-----
iG0EABECAC0WIQT0tgzFv3jCIUoxPcsxR9QN2y37KQUCZfwsHg8cZ3JlZ0Brcm9h
aC5jb20ACgkQMUfUDdst+ynT4ACePcNRAsYrINlOPPKPHimJtyP01yEAn0pZYnj2
0/UpqIqf3HVPu7zsLKTa
=vR9S
-----END PGP SIGNATURE-----
Merge tag 'driver-core-6.9-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core
Pull driver core updates from Greg KH:
"Here is the "big" set of driver core and kernfs changes for 6.9-rc1.
Nothing all that crazy here, just some good updates that include:
- automatic attribute group hiding from Dan Williams (he fixed up my
horrible attempt at doing this.)
- kobject lock contention fixes from Eric Dumazet
- driver core cleanups from Andy
- kernfs rcu work from Tejun
- fw_devlink changes to resolve some reported issues
- other minor changes, all details in the shortlog
All of these have been in linux-next for a long time with no reported
issues"
* tag 'driver-core-6.9-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core: (28 commits)
device: core: Log warning for devices pending deferred probe on timeout
driver: core: Use dev_* instead of pr_* so device metadata is added
driver: core: Log probe failure as error and with device metadata
of: property: fw_devlink: Add support for "post-init-providers" property
driver core: Add FWLINK_FLAG_IGNORE to completely ignore a fwnode link
driver core: Adds flags param to fwnode_link_add()
debugfs: fix wait/cancellation handling during remove
device property: Don't use "proxy" headers
device property: Move enum dev_dma_attr to fwnode.h
driver core: Move fw_devlink stuff to where it belongs
driver core: Drop unneeded 'extern' keyword in fwnode.h
firmware_loader: Suppress warning on FW_OPT_NO_WARN flag
sysfs:Addresses documentation in sysfs_merge_group and sysfs_unmerge_group.
firmware_loader: introduce __free() cleanup hanler
platform-msi: Remove usage of the deprecated ida_simple_xx() API
sysfs: Introduce DEFINE_SIMPLE_SYSFS_GROUP_VISIBLE()
sysfs: Document new "group visible" helpers
sysfs: Fix crash on empty group attributes array
sysfs: Introduce a mechanism to hide static attribute_groups
sysfs: Introduce a mechanism to hide static attribute_groups
...
- Standardize on prefixing scheduler-internal functions defined
in <linux/sched.h> with sched_*() prefix. scheduler_tick() was
the only function using the scheduler_ prefix. Harmonize it.
- The other reason to rename it is the NOHZ scheduler tick
handling functions are already named sched_tick_*().
Make the 'git grep sched_tick' more meaningful.
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Valentin Schneider <vschneid@redhat.com>
Reviewed-by: Shrikanth Hegde <sshegde@linux.ibm.com>
Link: https://lore.kernel.org/r/20240308111819.1101550-3-mingo@kernel.org
- The hierarchical timer pull model
When timer wheel timers are armed they are placed into the timer wheel
of a CPU which is likely to be busy at the time of expiry. This is done
to avoid wakeups on potentially idle CPUs.
This is wrong in several aspects:
1) The heuristics to select the target CPU are wrong by
definition as the chance to get the prediction right is close
to zero.
2) Due to #1 it is possible that timers are accumulated on a
single target CPU
3) The required computation in the enqueue path is just overhead for
dubious value especially under the consideration that the vast
majority of timer wheel timers are either canceled or rearmed
before they expire.
The timer pull model avoids the above by removing the target
computation on enqueue and queueing timers always on the CPU on which
they get armed.
This is achieved by having separate wheels for CPU pinned timers and
global timers which do not care about where they expire.
As long as a CPU is busy it handles both the pinned and the global
timers which are queued on the CPU local timer wheels.
When a CPU goes idle it evaluates its own timer wheels:
- If the first expiring timer is a pinned timer, then the global
timers can be ignored as the CPU will wake up before they expire.
- If the first expiring timer is a global timer, then the expiry time
is propagated into the timer pull hierarchy and the CPU makes sure
to wake up for the first pinned timer.
The timer pull hierarchy organizes CPUs in groups of eight at the
lowest level and at the next levels groups of eight groups up to the
point where no further aggregation of groups is required, i.e. the
number of levels is log8(NR_CPUS). The magic number of eight has been
established by experimention, but can be adjusted if needed.
In each group one busy CPU acts as the migrator. It's only one CPU to
avoid lock contention on remote timer wheels.
The migrator CPU checks in its own timer wheel handling whether there
are other CPUs in the group which have gone idle and have global timers
to expire. If there are global timers to expire, the migrator locks the
remote CPU timer wheel and handles the expiry.
Depending on the group level in the hierarchy this handling can require
to walk the hierarchy downwards to the CPU level.
Special care is taken when the last CPU goes idle. At this point the
CPU is the systemwide migrator at the top of the hierarchy and it
therefore cannot delegate to the hierarchy. It needs to arm its own
timer device to expire either at the first expiring timer in the
hierarchy or at the first CPU local timer, which ever expires first.
This completely removes the overhead from the enqueue path, which is
e.g. for networking a true hotpath and trades it for a slightly more
complex idle path.
This has been in development for a couple of years and the final series
has been extensively tested by various teams from silicon vendors and
ran through extensive CI.
There have been slight performance improvements observed on network
centric workloads and an Intel team confirmed that this allows them to
power down a die completely on a mult-die socket for the first time in
a mostly idle scenario.
There is only one outstanding ~1.5% regression on a specific overloaded
netperf test which is currently investigated, but the rest is either
positive or neutral performance wise and positive on the power
management side.
- Fixes for the timekeeping interpolation code for cross-timestamps:
cross-timestamps are used for PTP to get snapshots from hardware timers
and interpolated them back to clock MONOTONIC. The changes address a
few corner cases in the interpolation code which got the math and logic
wrong.
- Simplifcation of the clocksource watchdog retry logic to automatically
adjust to handle larger systems correctly instead of having more
incomprehensible command line parameters.
- Treewide consolidation of the VDSO data structures.
- The usual small improvements and cleanups all over the place.
-----BEGIN PGP SIGNATURE-----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=iQlu
-----END PGP SIGNATURE-----
Merge tag 'timers-core-2024-03-10' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull timer updates from Thomas Gleixner:
"A large set of updates and features for timers and timekeeping:
- The hierarchical timer pull model
When timer wheel timers are armed they are placed into the timer
wheel of a CPU which is likely to be busy at the time of expiry.
This is done to avoid wakeups on potentially idle CPUs.
This is wrong in several aspects:
1) The heuristics to select the target CPU are wrong by
definition as the chance to get the prediction right is
close to zero.
2) Due to #1 it is possible that timers are accumulated on
a single target CPU
3) The required computation in the enqueue path is just overhead
for dubious value especially under the consideration that the
vast majority of timer wheel timers are either canceled or
rearmed before they expire.
The timer pull model avoids the above by removing the target
computation on enqueue and queueing timers always on the CPU on
which they get armed.
This is achieved by having separate wheels for CPU pinned timers
and global timers which do not care about where they expire.
As long as a CPU is busy it handles both the pinned and the global
timers which are queued on the CPU local timer wheels.
When a CPU goes idle it evaluates its own timer wheels:
- If the first expiring timer is a pinned timer, then the global
timers can be ignored as the CPU will wake up before they
expire.
- If the first expiring timer is a global timer, then the expiry
time is propagated into the timer pull hierarchy and the CPU
makes sure to wake up for the first pinned timer.
The timer pull hierarchy organizes CPUs in groups of eight at the
lowest level and at the next levels groups of eight groups up to
the point where no further aggregation of groups is required, i.e.
the number of levels is log8(NR_CPUS). The magic number of eight
has been established by experimention, but can be adjusted if
needed.
In each group one busy CPU acts as the migrator. It's only one CPU
to avoid lock contention on remote timer wheels.
The migrator CPU checks in its own timer wheel handling whether
there are other CPUs in the group which have gone idle and have
global timers to expire. If there are global timers to expire, the
migrator locks the remote CPU timer wheel and handles the expiry.
Depending on the group level in the hierarchy this handling can
require to walk the hierarchy downwards to the CPU level.
Special care is taken when the last CPU goes idle. At this point
the CPU is the systemwide migrator at the top of the hierarchy and
it therefore cannot delegate to the hierarchy. It needs to arm its
own timer device to expire either at the first expiring timer in
the hierarchy or at the first CPU local timer, which ever expires
first.
This completely removes the overhead from the enqueue path, which
is e.g. for networking a true hotpath and trades it for a slightly
more complex idle path.
This has been in development for a couple of years and the final
series has been extensively tested by various teams from silicon
vendors and ran through extensive CI.
There have been slight performance improvements observed on network
centric workloads and an Intel team confirmed that this allows them
to power down a die completely on a mult-die socket for the first
time in a mostly idle scenario.
There is only one outstanding ~1.5% regression on a specific
overloaded netperf test which is currently investigated, but the
rest is either positive or neutral performance wise and positive on
the power management side.
- Fixes for the timekeeping interpolation code for cross-timestamps:
cross-timestamps are used for PTP to get snapshots from hardware
timers and interpolated them back to clock MONOTONIC. The changes
address a few corner cases in the interpolation code which got the
math and logic wrong.
- Simplifcation of the clocksource watchdog retry logic to
automatically adjust to handle larger systems correctly instead of
having more incomprehensible command line parameters.
- Treewide consolidation of the VDSO data structures.
- The usual small improvements and cleanups all over the place"
* tag 'timers-core-2024-03-10' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (62 commits)
timer/migration: Fix quick check reporting late expiry
tick/sched: Fix build failure for CONFIG_NO_HZ_COMMON=n
vdso/datapage: Quick fix - use asm/page-def.h for ARM64
timers: Assert no next dyntick timer look-up while CPU is offline
tick: Assume timekeeping is correctly handed over upon last offline idle call
tick: Shut down low-res tick from dying CPU
tick: Split nohz and highres features from nohz_mode
tick: Move individual bit features to debuggable mask accesses
tick: Move got_idle_tick away from common flags
tick: Assume the tick can't be stopped in NOHZ_MODE_INACTIVE mode
tick: Move broadcast cancellation up to CPUHP_AP_TICK_DYING
tick: Move tick cancellation up to CPUHP_AP_TICK_DYING
tick: Start centralizing tick related CPU hotplug operations
tick/sched: Don't clear ts::next_tick again in can_stop_idle_tick()
tick/sched: Rename tick_nohz_stop_sched_tick() to tick_nohz_full_stop_tick()
tick: Use IS_ENABLED() whenever possible
tick/sched: Remove useless oneshot ifdeffery
tick/nohz: Remove duplicate between lowres and highres handlers
tick/nohz: Remove duplicate between tick_nohz_switch_to_nohz() and tick_setup_sched_timer()
hrtimer: Select housekeeping CPU during migration
...
Boqun pointed out that workqueues aren't handling BH work items on offlined
CPUs. Unlike tasklet which transfers out the pending tasks from
CPUHP_SOFTIRQ_DEAD, BH workqueue would just leave them pending which is
problematic. Note that this behavior is specific to BH workqueues as the
non-BH per-CPU workers just become unbound when the CPU goes offline.
This patch fixes the issue by draining the pending BH work items from an
offlined CPU from CPUHP_SOFTIRQ_DEAD. Because work items carry more context,
it's not as easy to transfer the pending work items from one pool to
another. Instead, run BH work items which execute the offlined pools on an
online CPU.
Note that this assumes that no further BH work items will be queued on the
offlined CPUs. This assumption is shared with tasklet and should be fine for
conversions. However, this issue also exists for per-CPU workqueues which
will just keep executing work items queued after CPU offline on unbound
workers and workqueue should reject per-CPU and BH work items queued on
offline CPUs. This will be addressed separately later.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-and-reviewed-by: Boqun Feng <boqun.feng@gmail.com>
Link: http://lkml.kernel.org/r/Zdvw0HdSXcU3JZ4g@boqun-archlinux
When CONFIG_WQ_CPU_INTENSIVE_REPORT is set, the kernel will report
the work functions which violate the intensive_threshold_us repeatedly.
And now, only when the violate times exceed 4 and is a power of 2,
the kernel warning could be triggered.
However, sometimes, even if a long work execution time occurs only once,
it may cause other work to be delayed for a long time. This may also
cause some problems sometimes.
In order to freely control the threshold of warninging, a boot argument
is added so that the user can control the warning threshold to be printed.
At the same time, keep the exponential backoff to prevent reporting too much.
By default, the warning threshold is 4.
tj: Updated kernel-parameters.txt description.
Signed-off-by: Xuewen Yan <xuewen.yan@unisoc.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
The implementation of the NOHZ pull at expiry model will change the timer
bases per CPU. Timers, that have to expire on a specific CPU, require the
TIMER_PINNED flag. If the CPU doesn't matter, the TIMER_PINNED flag must be
dropped. This is required for call sites which use the timer alternately as
pinned and not pinned timer like workqueues do.
Therefore use add_timer_global() in __queue_delayed_work() for non-bound
delayed work to make sure the TIMER_PINNED flag is dropped.
Signed-off-by: Anna-Maria Behnsen <anna-maria@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Acked-by: Tejun Heo <tj@kernel.org>
Link: https://lore.kernel.org/r/20240221090548.36600-7-anna-maria@linutronix.de
- set_work_data() takes a separate @flags argument but just ORs it to @data.
This is more confusing than helpful. Just take @data.
- Use the name @flags consistently and add the parameter to
set_work_pool_and_{keep|clear}_pending(). This will be used by the planned
disable/enable support.
No functional changes.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Lai Jiangshan <jiangshanlai@gmail.com>
clear_work_data() is only used in one place and immediately followed by
smp_mb(), making it equivalent to set_work_pool_and_clear_pending() w/
WORK_OFFQ_POOL_NONE for @pool_id. Drop it. No functional changes.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Lai Jiangshan <jiangshanlai@gmail.com>
The planned disable/enable support will need the same logic. Let's factor it
out. No functional changes.
v2: Update function comment to include @irq_flags.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Lai Jiangshan <jiangshanlai@gmail.com>
The bits of work->data are used for a few different purposes. How the bits
are used is determined by enum work_bits. The planned disable/enable support
will add another use, so let's clean it up a bit in preparation.
- Let WORK_STRUCT_*_BIT's values be determined by enum definition order.
- Deliminate different bit sections the same way using SHIFT and BITS
values.
- Rename __WORK_OFFQ_CANCELING to WORK_OFFQ_CANCELING_BIT for consistency.
- Introduce WORK_STRUCT_PWQ_SHIFT and replace WORK_STRUCT_FLAG_MASK and
WORK_STRUCT_WQ_DATA_MASK with WQ_STRUCT_PWQ_MASK for clarity.
- Improve documentation.
No functional changes.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Lai Jiangshan <jiangshanlai@gmail.com>
The cancel path used bool @is_dwork to distinguish canceling a regular work
and a delayed one. The planned disable/enable support will need passing
around another flag in the code path. As passing them around with bools will
be confusing, let's introduce named flags to pass around in the cancel path.
WORK_CANCEL_DELAYED replaces @is_dwork. No functional changes.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Lai Jiangshan <jiangshanlai@gmail.com>
Using the generic term `flags` for irq flags is conventional but can be
confusing as there's quite a bit of code dealing with work flags which
involves some subtleties. Let's use a more explicit name `irq_flags` for
local irq flags. No functional changes.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Lai Jiangshan <jiangshanlai@gmail.com>
They are currently a bit disorganized with flush and cancel functions mixed.
Reoranize them so that flush functions come first, cancel next and
cancel_sync last. This way, we won't have to add prototypes for internal
functions for the planned disable/enable support.
This is pure code reorganization. No functional changes.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Lai Jiangshan <jiangshanlai@gmail.com>
__cancel_work_timer() is used to implement cancel_work_sync() and
cancel_delayed_work_sync(), similarly to how __cancel_work() is used to
implement cancel_work() and cancel_delayed_work(). ie. The _timer part of
the name is a complete misnomer. The difference from __cancel_work() is the
fact that it syncs against work item execution not whether it handles timers
or not.
Let's rename it to less confusing __cancel_work_sync(). No functional
change.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Lai Jiangshan <jiangshanlai@gmail.com>
The different flavors of RCU read critical sections have been unified. Let's
update the locking assertion macros accordingly to avoid requiring
unnecessary explicit rcu_read_[un]lock() calls.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Lai Jiangshan <jiangshanlai@gmail.com>
Reorder some global declarations and adjust comments and whitespaces for
clarity and consistency. No functional changes.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Lai Jiangshan <jiangshanlai@gmail.com>
-----BEGIN PGP SIGNATURE-----
iQFSBAABCAA8FiEEq68RxlopcLEwq+PEeb4+QwBBGIYFAmXSbvkeHHRvcnZhbGRz
QGxpbnV4LWZvdW5kYXRpb24ub3JnAAoJEHm+PkMAQRiGi3kH/iM5AcKeQfee07to
TJP3WORLBt5UrUMgAQbJdNAruCj6brHA6YnZ6AjdhdNZ41RO06h69kTpb+y/CYJz
+ogGK5qhWsC8ETM6rJCioo8uI4GU70p84fGiMfLw8o6vUvmtyI5qH3531Y30Edxt
qqMVtQrVe9J5JcHQjJ/mQo8nAuvZdQQGM90zLGqFP+JheP3CzsCokraIITqoebDC
PCVAsnSbXT/uMjwSr03kdnMnnY++fxz/TyHb/QRMPq/4xU8nz0Z2hlOOYrVkOINu
lkIYtCDGTk0QR3hdDiO9yt+k1OsWi+oBkrhjAQmAk9x3riiXq1NKvZZLDArt7PH5
gSyo9sE=
=h5Ei
-----END PGP SIGNATURE-----
Merge 6.8-rc5 into driver-core-next
We need the driver core changes in here as well.
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2f34d7337d ("workqueue: Fix queue_work_on() with BH workqueues") added
irq_work usage to workqueue; however, it turns out irq_work is actually
optional and the change breaks build on configuration which doesn't have
CONFIG_IRQ_WORK enabled.
Fix build by making workqueue use irq_work only when CONFIG_SMP and enabling
CONFIG_IRQ_WORK when CONFIG_SMP is set. It's reasonable to argue that it may
be better to just always enable it. However, this still saves a small bit of
memory for tiny UP configs and also the least amount of change, so, for now,
let's keep it conditional.
Verified to do the right thing for x86_64 allnoconfig and defconfig, and
aarch64 allnoconfig, allnoconfig + prink disable (SMP but nothing selects
IRQ_WORK) and a modified aarch64 Kconfig where !SMP and nothing selects
IRQ_WORK.
v2: `depends on SMP` leads to Kconfig warnings when CONFIG_IRQ_WORK is
selected by something else when !CONFIG_SMP. Use `def_bool y if SMP`
instead.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-by: Naresh Kamboju <naresh.kamboju@linaro.org>
Tested-by: Anders Roxell <anders.roxell@linaro.org>
Fixes: 2f34d7337d ("workqueue: Fix queue_work_on() with BH workqueues")
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
When queue_work_on() is used to queue a BH work item on a remote CPU, the
work item is queued on that CPU but kick_pool() raises softirq on the local
CPU. This leads to stalls as the work item won't be executed until something
else on the remote CPU schedules a BH work item or tasklet locally.
Fix it by bouncing raising softirq to the target CPU using per-cpu irq_work.
Signed-off-by: Tejun Heo <tj@kernel.org>
Fixes: 4cb1ef6460 ("workqueue: Implement BH workqueues to eventually replace tasklets")
Since 5797b1c189 ("workqueue: Implement system-wide nr_active enforcement
for unbound workqueues"), unbound workqueues have separate min_active which
sets the number of interdependent work items that can be handled. This value
is currently initialized to WQ_DFL_MIN_ACTIVE which is 8. This isn't high
enough for some users, let's add an interface to adjust the setting.
Signed-off-by: Tejun Heo <tj@kernel.org>
Fix the kernel-doc comment of the unplug_oldest_pwq() function to enable
proper processing and formatting of the embedded ASCII diagram.
Signed-off-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Commit 85f0ab43f9 ("kernel/workqueue: Bind rescuer to unbound
cpumask for WQ_UNBOUND") modified init_rescuer() to bind rescuer of
an unbound workqueue to the cpumask in wq->unbound_attrs. However
unbound_attrs->cpumask's of all workqueues are initialized to
cpu_possible_mask and will only be changed if it has the WQ_SYSFS flag
to expose a cpumask sysfs file to be written by users. So this patch
doesn't achieve what it is intended to do.
If an unbound workqueue is created after wq_unbound_cpumask is modified
and there is no more unbound cpumask update after that, the unbound
rescuer will be bound to all CPUs unless the workqueue is created
with the WQ_SYSFS flag and a user explicitly modified its cpumask
sysfs file. Fix this problem by binding directly to wq_unbound_cpumask
in init_rescuer().
Fixes: 85f0ab43f9 ("kernel/workqueue: Bind rescuer to unbound cpumask for WQ_UNBOUND")
Signed-off-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
When workqueue cpumask changes are committed the associated rescuer (if
one exists) affinity is not touched and this might be a problem down the
line for isolated setups.
Make sure rescuers affinity is updated every time a workqueue cpumask
changes, so that rescuers can't break isolation.
[longman: set_cpus_allowed_ptr() will block until the designated task
is enqueued on an allowed CPU, no wake_up_process() needed. Also use
the unbound_effective_cpumask() helper as suggested by Tejun.]
Signed-off-by: Juri Lelli <juri.lelli@redhat.com>
Signed-off-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Ordered workqueues does not currently follow changes made to the
global unbound cpumask because per-pool workqueue changes may break
the ordering guarantee. IOW, a work function in an ordered workqueue
may run on an isolated CPU.
This patch enables ordered workqueues to follow changes made to the
global unbound cpumask by temporaily plug or suspend the newly allocated
pool_workqueue from executing newly queued work items until the old
pwq has been properly drained. For ordered workqueues, there should
only be one pwq that is unplugged, the rests should be plugged.
This enables ordered workqueues to follow the unbound cpumask changes
like other unbound workqueues at the expense of some delay in execution
of work functions during the transition period.
Signed-off-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Add a new pwq into the tail of wq->pwqs so that pwq iteration will
start from the oldest pwq to the newest. This ordering will facilitate
the inclusion of ordered workqueues in a wq_unbound_cpumask update.
Signed-off-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Now that the driver core can properly handle constant struct bus_type,
move the wq_subsys variable to be a constant structure as well,
placing it into read-only memory which can not be modified at runtime.
Suggested-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: "Ricardo B. Marliere" <ricardo@marliere.net>
Cc: Tejun Heo <tj@kernel.org>
Link: https://lore.kernel.org/r/20240206-bus_cleanup-workqueue-v1-1-72b10d282d58@marliere.net
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
The for-6.8-fixes commit ae9cc8956944 ("Revert "workqueue: Override implicit
ordered attribute in workqueue_apply_unbound_cpumask()") also fixes build for
Signed-off-by: Tejun Heo <tj@kernel.org>
This reverts commit ca10d851b9.
The commit allowed workqueue_apply_unbound_cpumask() to clear __WQ_ORDERED
on now removed implicitly ordered workqueues. This was incorrect in that
system-wide config change shouldn't break ordering properties of all
workqueues. The reason why apply_workqueue_attrs() path was allowed to do so
was because it was targeting the specific workqueue - either the workqueue
had WQ_SYSFS set or the workqueue user specifically tried to change
max_active, both of which indicate that the workqueue doesn't need to be
ordered.
The implicitly ordered workqueue promotion was removed by the previous
commit 3bc1e711c2 ("workqueue: Don't implicitly make UNBOUND workqueues w/
@max_active==1 ordered"). However, it didn't update this path and broke
build. Let's revert the commit which was incorrect in the first place which
also fixes build.
Signed-off-by: Tejun Heo <tj@kernel.org>
Fixes: 3bc1e711c2 ("workqueue: Don't implicitly make UNBOUND workqueues w/ @max_active==1 ordered")
Fixes: ca10d851b9 ("workqueue: Override implicit ordered attribute in workqueue_apply_unbound_cpumask()")
Cc: stable@vger.kernel.org # v6.6+
Signed-off-by: Tejun Heo <tj@kernel.org>
5c0338c687 ("workqueue: restore WQ_UNBOUND/max_active==1 to be ordered")
automoatically promoted UNBOUND workqueues w/ @max_active==1 to ordered
workqueues because UNBOUND workqueues w/ @max_active==1 used to be the way
to create ordered workqueues and the new NUMA support broke it. These
problems can be subtle and the fact that they can only trigger on NUMA
machines made them even more difficult to debug.
However, overloading the UNBOUND allocation interface this way creates other
issues. It's difficult to tell whether a given workqueue actually needs to
be ordered and users that legitimately want a min concurrency level wq
unexpectedly gets an ordered one instead. With planned UNBOUND workqueue
udpates to improve execution locality and more prevalence of chiplet designs
which can benefit from such improvements, this isn't a state we wanna be in
forever.
There aren't that many UNBOUND w/ @max_active==1 users in the tree and the
preceding patches audited all and converted them to
alloc_ordered_workqueue() as appropriate. This patch removes the implicit
promotion of UNBOUND w/ @max_active==1 workqueues to ordered ones.
v2: v1 patch incorrectly dropped !list_empty(&wq->pwqs) condition in
apply_workqueue_attrs_locked() which spuriously triggers WARNING and
fails workqueue creation. Fix it.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-by: kernel test robot <oliver.sang@intel.com>
Link: https://lore.kernel.org/oe-lkp/202304251050.45a5df1f-oliver.sang@intel.com
Skip updating workqueues with __WQ_DESTROYING bit set when updating
global unbound cpumask to avoid unnecessary work and other complications.
Signed-off-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
This reverts commit d412ace111. This leads to
build failures as it depends on a driver-core commit 32f78abe59 ("driver
core: bus: constantify subsys_register() calls"). Let's drop it from wq tree
and route it through driver-core tree.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202402051505.kM9Rr3CJ-lkp@intel.com/
The only generic interface to execute asynchronously in the BH context is
tasklet; however, it's marked deprecated and has some design flaws such as
the execution code accessing the tasklet item after the execution is
complete which can lead to subtle use-after-free in certain usage scenarios
and less-developed flush and cancel mechanisms.
This patch implements BH workqueues which share the same semantics and
features of regular workqueues but execute their work items in the softirq
context. As there is always only one BH execution context per CPU, none of
the concurrency management mechanisms applies and a BH workqueue can be
thought of as a convenience wrapper around softirq.
Except for the inability to sleep while executing and lack of max_active
adjustments, BH workqueues and work items should behave the same as regular
workqueues and work items.
Currently, the execution is hooked to tasklet[_hi]. However, the goal is to
convert all tasklet users over to BH workqueues. Once the conversion is
complete, tasklet can be removed and BH workqueues can directly take over
the tasklet softirqs.
system_bh[_highpri]_wq are added. As queue-wide flushing doesn't exist in
tasklet, all existing tasklet users should be able to use the system BH
workqueues without creating their own workqueues.
v3: - Add missing interrupt.h include.
v2: - Instead of using tasklets, hook directly into its softirq action
functions - tasklet[_hi]_action(). This is slightly cheaper and closer
to the eventual code structure we want to arrive at. Suggested by Lai.
- Lai also pointed out several places which need NULL worker->task
handling or can use clarification. Updated.
Signed-off-by: Tejun Heo <tj@kernel.org>
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/CAHk-=wjDW53w4-YcSmgKC5RruiRLHmJ1sXeYdp_ZgVoBw=5byA@mail.gmail.com
Tested-by: Allen Pais <allen.lkml@gmail.com>
Reviewed-by: Lai Jiangshan <jiangshanlai@gmail.com>
Factor out init_cpu_worker_pool() from workqueue_init_early(). This is pure
reorganization in preparation of BH workqueue support.
Signed-off-by: Tejun Heo <tj@kernel.org>
Tested-by: Allen Pais <allen.lkml@gmail.com>
