unimore/kernel-hacking-2024-linux-steffo
unimore/kernel-hacking-2024-linux-steffo
1
Fork 0
Code Pull requests 5 Wiki Activity

mm: page_alloc: exempt GFP_THISNODE allocations from zone fairness

Browse source 
Jan Stancek reports manual page migration encountering allocation
failures after some pages when there is still plenty of memory free, and
bisected the problem down to commit 81c0a2bb51 ("mm: page_alloc: fair
zone allocator policy").

The problem is that GFP_THISNODE obeys the zone fairness allocation
batches on one hand, but doesn't reset them and wake kswapd on the other
hand.  After a few of those allocations, the batches are exhausted and
the allocations fail.

Fixing this means either having GFP_THISNODE wake up kswapd, or
GFP_THISNODE not participating in zone fairness at all.  The latter
seems safer as an acute bugfix, we can clean up later.

Reported-by: Jan Stancek <jstancek@redhat.com>
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Rik van Riel <riel@redhat.com>
Acked-by: Mel Gorman <mgorman@suse.de>
Cc: <stable@kernel.org>		[3.12+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Johannes Weiner 2014-03-03 15:38:41 -08:00 committed by Linus Torvalds
parent 1ae71d0319
commit 27329369c9
1 changed files with 22 additions and 4 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

26
mm/page_alloc.c
View file

@ -1238,6 +1238,15 @@ void drain_zone_pages(struct zone *zone, struct per_cpu_pages *pcp)
}
local_irq_restore(flags);
}
static bool gfp_thisnode_allocation(gfp_t gfp_mask)
{
return (gfp_mask & GFP_THISNODE) == GFP_THISNODE;
}
#else
static bool gfp_thisnode_allocation(gfp_t gfp_mask)
{
return false;
}
#endif
/*
@ -1574,7 +1583,13 @@ struct page *buffered_rmqueue(struct zone *preferred_zone,
get_pageblock_migratetype(page));
}
__mod_zone_page_state(zone, NR_ALLOC_BATCH, -(1 << order));
/*
* NOTE: GFP_THISNODE allocations do not partake in the kswapd
* aging protocol, so they can't be fair.
*/
if (!gfp_thisnode_allocation(gfp_flags))
__mod_zone_page_state(zone, NR_ALLOC_BATCH, -(1 << order));
__count_zone_vm_events(PGALLOC, zone, 1 << order);
zone_statistics(preferred_zone, zone, gfp_flags);
local_irq_restore(flags);
@ -1946,8 +1961,12 @@ get_page_from_freelist(gfp_t gfp_mask, nodemask_t *nodemask, unsigned int order,
* ultimately fall back to remote zones that do not
* partake in the fairness round-robin cycle of this
* zonelist.
*
* NOTE: GFP_THISNODE allocations do not partake in
* the kswapd aging protocol, so they can't be fair.
*/
if (alloc_flags & ALLOC_WMARK_LOW) {
if ((alloc_flags & ALLOC_WMARK_LOW) &&
!gfp_thisnode_allocation(gfp_mask)) {
if (zone_page_state(zone, NR_ALLOC_BATCH) <= 0)
continue;
if (!zone_local(preferred_zone, zone))
@ -2503,8 +2522,7 @@ __alloc_pages_slowpath(gfp_t gfp_mask, unsigned int order,
* allowed per node queues are empty and that nodes are
* over allocated.
*/
if (IS_ENABLED(CONFIG_NUMA) &&
(gfp_mask & GFP_THISNODE) == GFP_THISNODE)
if (gfp_thisnode_allocation(gfp_mask))
goto nopage;
restart: