qemu/backends
Jitendra Kolhe 1e356fc14b mem-prealloc: reduce large guest start-up and migration time.
Using "-mem-prealloc" option for a large guest leads to higher guest
start-up and migration time. This is because with "-mem-prealloc" option
qemu tries to map every guest page (create address translations), and
make sure the pages are available during runtime. virsh/libvirt by
default, seems to use "-mem-prealloc" option in case the guest is
configured to use huge pages. The patch tries to map all guest pages
simultaneously by spawning multiple threads. Currently limiting the
change to QEMU library functions on POSIX compliant host only, as we are
not sure if the problem exists on win32. Below are some stats with
"-mem-prealloc" option for guest configured to use huge pages.

------------------------------------------------------------------------
Idle Guest      | Start-up time | Migration time
------------------------------------------------------------------------
Guest stats with 2M HugePage usage - single threaded (existing code)
------------------------------------------------------------------------
64 Core - 4TB   | 54m11.796s    | 75m43.843s
64 Core - 1TB   | 8m56.576s     | 14m29.049s
64 Core - 256GB | 2m11.245s     | 3m26.598s
------------------------------------------------------------------------
Guest stats with 2M HugePage usage - map guest pages using 8 threads
------------------------------------------------------------------------
64 Core - 4TB   | 5m1.027s      | 34m10.565s
64 Core - 1TB   | 1m10.366s     | 8m28.188s
64 Core - 256GB | 0m19.040s     | 2m10.148s
-----------------------------------------------------------------------
Guest stats with 2M HugePage usage - map guest pages using 16 threads
-----------------------------------------------------------------------
64 Core - 4TB   | 1m58.970s     | 31m43.400s
64 Core - 1TB   | 0m39.885s     | 7m55.289s
64 Core - 256GB | 0m11.960s     | 2m0.135s
-----------------------------------------------------------------------

Changed in v2:
 - modify number of memset threads spawned to min(smp_cpus, 16).
 - removed 64GB memory restriction for spawning memset threads.

Changed in v3:
 - limit number of threads spawned based on
   min(sysconf(_SC_NPROCESSORS_ONLN), 16, smp_cpus)
 - implement memset thread specific siglongjmp in SIGBUS signal_handler.

Changed in v4
 - remove sigsetjmp/siglongjmp and SIGBUS unblock/block for main thread
   as main thread no longer touches any pages.
 - simplify code my returning memset_thread_failed status from
   touch_all_pages.

Signed-off-by: Jitendra Kolhe <jitendra.kolhe@hpe.com>
Message-Id: <1487907103-32350-1-git-send-email-jitendra.kolhe@hpe.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2017-03-14 13:26:36 +01:00
..
baum.c char: remove class kind field 2017-01-31 13:03:42 +04:00
cryptodev-builtin.c cryptodev: wrap the ready flag 2017-01-10 07:02:52 +02:00
cryptodev.c cryptodev: wrap the ready flag 2017-01-10 07:02:52 +02:00
hostmem-file.c hostmem-file: Register TYPE_MEMORY_BACKEND_FILE properties as class properties 2016-10-17 15:48:40 -02:00
hostmem-ram.c include/qemu/osdep.h: Don't include qapi/error.h 2016-03-22 22:20:15 +01:00
hostmem.c mem-prealloc: reduce large guest start-up and migration time. 2017-03-14 13:26:36 +01:00
Makefile.objs Add wctablet device 2017-02-20 11:26:28 +01:00
msmouse.c char: remove class kind field 2017-01-31 13:03:42 +04:00
rng-egd.c char: rename CharDriverState Chardev 2017-01-27 18:07:59 +01:00
rng-random.c rng-random: rename RndRandom to RngRandom 2016-05-23 12:18:43 +05:30
rng.c include/qemu/osdep.h: Don't include qapi/error.h 2016-03-22 22:20:15 +01:00
testdev.c char: remove class kind field 2017-01-31 13:03:42 +04:00
tpm.c include/qemu/osdep.h: Don't include qapi/error.h 2016-03-22 22:20:15 +01:00
trace-events Add wctablet device 2017-02-20 11:26:28 +01:00
wctablet.c Add wctablet device 2017-02-20 11:26:28 +01:00