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page allocator: calculate the alloc_flags for allocation only once 

Factor out the mapping between GFP and alloc_flags only once.  Once
factored out, it only needs to be calculated once but some care must be
taken.

[neilb@suse.de says]
As the test:

-       if (((p->flags & PF_MEMALLOC) || unlikely(test_thread_flag(TIF_MEMDIE)))
-                       && !in_interrupt()) {
-               if (!(gfp_mask & __GFP_NOMEMALLOC)) {

has been replaced with a slightly weaker one:

+       if (alloc_flags & ALLOC_NO_WATERMARKS) {

Without care, this would allow recursion into the allocator via direct
reclaim.  This patch ensures we do not recurse when PF_MEMALLOC is set but
TF_MEMDIE callers are now allowed to directly reclaim where they would
have been prevented in the past.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: Pekka Enberg <penberg@cs.helsinki.fi>
Signed-off-by: Mel Gorman <mel@csn.ul.ie>
Cc: Neil Brown <neilb@suse.de>
Cc: Christoph Lameter <cl@linux-foundation.org>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: Dave Hansen <dave@linux.vnet.ibm.com>
Cc: Lee Schermerhorn <Lee.Schermerhorn@hp.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Peter Zijlstra 2009-06-16 15:32:02 -07:00 committed by Linus Torvalds
parent 3dd2826698
commit 341ce06f69
1 changed files with 50 additions and 44 deletions
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94
mm/page_alloc.c
View File

@ -1574,15 +1574,6 @@ __alloc_pages_direct_reclaim(gfp_t gfp_mask, unsigned int order,
return page;
}
static inline int
is_allocation_high_priority(struct task_struct *p, gfp_t gfp_mask)
{
if (((p->flags & PF_MEMALLOC) || unlikely(test_thread_flag(TIF_MEMDIE)))
&& !in_interrupt())
return 1;
return 0;
}
/*
* This is called in the allocator slow-path if the allocation request is of
* sufficient urgency to ignore watermarks and take other desperate measures
@ -1618,6 +1609,42 @@ void wake_all_kswapd(unsigned int order, struct zonelist *zonelist,
wakeup_kswapd(zone, order);
}
static inline int
gfp_to_alloc_flags(gfp_t gfp_mask)
{
struct task_struct *p = current;
int alloc_flags = ALLOC_WMARK_MIN | ALLOC_CPUSET;
const gfp_t wait = gfp_mask & __GFP_WAIT;
/*
* The caller may dip into page reserves a bit more if the caller
* cannot run direct reclaim, or if the caller has realtime scheduling
* policy or is asking for __GFP_HIGH memory. GFP_ATOMIC requests will
* set both ALLOC_HARDER (!wait) and ALLOC_HIGH (__GFP_HIGH).
*/
if (gfp_mask & __GFP_HIGH)
alloc_flags |= ALLOC_HIGH;
if (!wait) {
alloc_flags |= ALLOC_HARDER;
/*
* Ignore cpuset if GFP_ATOMIC (!wait) rather than fail alloc.
* See also cpuset_zone_allowed() comment in kernel/cpuset.c.
*/
alloc_flags &= ~ALLOC_CPUSET;
} else if (unlikely(rt_task(p)))
alloc_flags |= ALLOC_HARDER;
if (likely(!(gfp_mask & __GFP_NOMEMALLOC))) {
if (!in_interrupt() &&
((p->flags & PF_MEMALLOC) ||
unlikely(test_thread_flag(TIF_MEMDIE))))
alloc_flags |= ALLOC_NO_WATERMARKS;
}
return alloc_flags;
}
static inline struct page *
__alloc_pages_slowpath(gfp_t gfp_mask, unsigned int order,
struct zonelist *zonelist, enum zone_type high_zoneidx,
@ -1648,56 +1675,35 @@ __alloc_pages_slowpath(gfp_t gfp_mask, unsigned int order,
* OK, we're below the kswapd watermark and have kicked background
* reclaim. Now things get more complex, so set up alloc_flags according
* to how we want to proceed.
*
* The caller may dip into page reserves a bit more if the caller
* cannot run direct reclaim, or if the caller has realtime scheduling
* policy or is asking for __GFP_HIGH memory. GFP_ATOMIC requests will
* set both ALLOC_HARDER (!wait) and ALLOC_HIGH (__GFP_HIGH).
*/
alloc_flags = ALLOC_WMARK_MIN;
if ((unlikely(rt_task(p)) && !in_interrupt()) || !wait)
alloc_flags |= ALLOC_HARDER;
if (gfp_mask & __GFP_HIGH)
alloc_flags |= ALLOC_HIGH;
if (wait)
alloc_flags |= ALLOC_CPUSET;
alloc_flags = gfp_to_alloc_flags(gfp_mask);
restart:
/*
* Go through the zonelist again. Let __GFP_HIGH and allocations
* coming from realtime tasks go deeper into reserves.
*
* This is the last chance, in general, before the goto nopage.
* Ignore cpuset if GFP_ATOMIC (!wait) rather than fail alloc.
* See also cpuset_zone_allowed() comment in kernel/cpuset.c.
*/
/* This is the last chance, in general, before the goto nopage. */
page = get_page_from_freelist(gfp_mask, nodemask, order, zonelist,
high_zoneidx, alloc_flags,
preferred_zone,
migratetype);
high_zoneidx, alloc_flags & ~ALLOC_NO_WATERMARKS,
preferred_zone, migratetype);
if (page)
goto got_pg;
rebalance:
/* Allocate without watermarks if the context allows */
if (is_allocation_high_priority(p, gfp_mask)) {
/* Do not dip into emergency reserves if specified */
if (!(gfp_mask & __GFP_NOMEMALLOC)) {
page = __alloc_pages_high_priority(gfp_mask, order,
zonelist, high_zoneidx, nodemask, preferred_zone,
migratetype);
if (page)
goto got_pg;
}
/* Ensure no recursion into the allocator */
goto nopage;
if (alloc_flags & ALLOC_NO_WATERMARKS) {
page = __alloc_pages_high_priority(gfp_mask, order,
zonelist, high_zoneidx, nodemask,
preferred_zone, migratetype);
if (page)
goto got_pg;
}
/* Atomic allocations - we can't balance anything */
if (!wait)
goto nopage;
/* Avoid recursion of direct reclaim */
if (p->flags & PF_MEMALLOC)
goto nopage;
/* Try direct reclaim and then allocating */
page = __alloc_pages_direct_reclaim(gfp_mask, order,
zonelist, high_zoneidx,