Matt Fleming 172703b08c mm: delete non-atomic mm counter implementation ... The problem with having two different types of counters is that developers adding new code need to keep in mind whether it's safe to use both the atomic and non-atomic implementations. For example, when adding new callers of the *_mm_counter() functions a developer needs to ensure that those paths are always executed with page_table_lock held, in case we're using the non-atomic implementation of mm counters. Hugh Dickins introduced the atomic mm counters in commit f412ac08c9 ("[PATCH] mm: fix rss and mmlist locking"). When asked why he left the non-atomic counters around he said, | The only reason was to avoid adding costly atomic operations into a | configuration that had no need for them there: the page_table_lock | sufficed. | | Certainly it would be simpler just to delete the non-atomic variant. | | And I think it's fair to say that any configuration on which we're | measuring performance to that degree (rather than "does it boot fast?" | type measurements), would already be going the split ptlocks route. Removing the non-atomic counters eases the maintenance burden because developers no longer have to mindful of the two implementations when using *_mm_counter(). Note that all architectures provide a means of atomically updating atomic_long_t variables, even if they have to revert to the generic spinlock implementation because they don't support 64-bit atomic instructions (see lib/atomic64.c). Signed-off-by: Matt Fleming <matt.fleming@linux.intel.com> Acked-by: Dave Hansen <dave@linux.vnet.ibm.com> Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Cc: Hugh Dickins <hughd@google.com> Cc: Christoph Lameter <cl@linux-foundation.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>		2011-05-25 08:39:30 -07:00
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acpi
asm-generic	mm: uninline large generic tlb.h functions	2011-05-25 08:39:20 -07:00
crypto
drm	Merge branch 'drm-core-next' of git://git.kernel.org/pub/scm/linux/kernel/git/airlied/drm-2.6	2011-05-24 12:06:40 -07:00
keys
linux	mm: delete non-atomic mm counter implementation	2011-05-25 08:39:30 -07:00
math-emu
media	[media] rc: add locking to fix register/show race	2011-05-20 16:21:22 -03:00
mtd
net	Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/trivial	2011-05-23 09:12:26 -07:00
pcmcia	pcmcia: Make declaration and uses of struct pcmcia_device_id const	2011-05-06 07:46:15 +02:00
rdma	Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next-2.6	2011-05-20 13:43:21 -07:00
rxrpc
scsi	scsi: remove performance regression due to async queue run	2011-05-17 11:04:44 +02:00
sound	Merge branch 'topic/asoc' into for-linus	2011-05-22 10:01:33 +02:00
staging
target
trace	Merge branch 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip	2011-05-19 18:14:34 -07:00
video
xen
Kbuild