From: Charan Teja Reddy charante@codeaurora.org
commit f80b08fc44536a311a9f3182e50f318b79076425 upstream.
When boosting is enabled, it is observed that rate of atomic order-0 allocation failures are high due to the fact that free levels in the system are checked with ->watermark_boost offset. This is not a problem for sleepable allocations but for atomic allocations which looks like regression.
This problem is seen frequently on system setup of Android kernel running on Snapdragon hardware with 4GB RAM size. When no extfrag event occurred in the system, ->watermark_boost factor is zero, thus the watermark configurations in the system are:
_watermark = ( [WMARK_MIN] = 1272, --> ~5MB [WMARK_LOW] = 9067, --> ~36MB [WMARK_HIGH] = 9385), --> ~38MB watermark_boost = 0
After launching some memory hungry applications in Android which can cause extfrag events in the system to an extent that ->watermark_boost can be set to max i.e. default boost factor makes it to 150% of high watermark.
_watermark = ( [WMARK_MIN] = 1272, --> ~5MB [WMARK_LOW] = 9067, --> ~36MB [WMARK_HIGH] = 9385), --> ~38MB watermark_boost = 14077, -->~57MB
With default system configuration, for an atomic order-0 allocation to succeed, having free memory of ~2MB will suffice. But boosting makes the min_wmark to ~61MB thus for an atomic order-0 allocation to be successful system should have minimum of ~23MB of free memory(from calculations of zone_watermark_ok(), min = 3/4(min/2)). But failures are observed despite system is having ~20MB of free memory. In the testing, this is reproducible as early as first 300secs since boot and with furtherlowram configurations(<2GB) it is observed as early as first 150secs since boot.
These failures can be avoided by excluding the ->watermark_boost in watermark caluculations for atomic order-0 allocations.
[akpm@linux-foundation.org: fix comment grammar, reflow comment] [charante@codeaurora.org: fix suggested by Mel Gorman] Link: http://lkml.kernel.org/r/31556793-57b1-1c21-1a9d-22674d9bd938@codeaurora.org
Signed-off-by: Charan Teja Reddy charante@codeaurora.org Signed-off-by: Andrew Morton akpm@linux-foundation.org Acked-by: Vlastimil Babka vbabka@suse.cz Cc: Vinayak Menon vinmenon@codeaurora.org Cc: Mel Gorman mgorman@techsingularity.net Link: http://lkml.kernel.org/r/1589882284-21010-1-git-send-email-charante@codeauro... Signed-off-by: Linus Torvalds torvalds@linux-foundation.org Signed-off-by: Ralph Siemsen ralph.siemsen@linaro.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- mm/page_alloc.c | 25 +++++++++++++++++++++---- 1 file changed, 21 insertions(+), 4 deletions(-)
--- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -3484,7 +3484,8 @@ bool zone_watermark_ok(struct zone *z, u }
static inline bool zone_watermark_fast(struct zone *z, unsigned int order, - unsigned long mark, int classzone_idx, unsigned int alloc_flags) + unsigned long mark, int classzone_idx, + unsigned int alloc_flags, gfp_t gfp_mask) { long free_pages = zone_page_state(z, NR_FREE_PAGES); long cma_pages = 0; @@ -3505,8 +3506,23 @@ static inline bool zone_watermark_fast(s if (!order && (free_pages - cma_pages) > mark + z->lowmem_reserve[classzone_idx]) return true;
- return __zone_watermark_ok(z, order, mark, classzone_idx, alloc_flags, - free_pages); + if (__zone_watermark_ok(z, order, mark, classzone_idx, alloc_flags, + free_pages)) + return true; + /* + * Ignore watermark boosting for GFP_ATOMIC order-0 allocations + * when checking the min watermark. The min watermark is the + * point where boosting is ignored so that kswapd is woken up + * when below the low watermark. + */ + if (unlikely(!order && (gfp_mask & __GFP_ATOMIC) && z->watermark_boost + && ((alloc_flags & ALLOC_WMARK_MASK) == WMARK_MIN))) { + mark = z->_watermark[WMARK_MIN]; + return __zone_watermark_ok(z, order, mark, classzone_idx, + alloc_flags, free_pages); + } + + return false; }
bool zone_watermark_ok_safe(struct zone *z, unsigned int order, @@ -3647,7 +3663,8 @@ retry:
mark = wmark_pages(zone, alloc_flags & ALLOC_WMARK_MASK); if (!zone_watermark_fast(zone, order, mark, - ac_classzone_idx(ac), alloc_flags)) { + ac_classzone_idx(ac), alloc_flags, + gfp_mask)) { int ret;
#ifdef CONFIG_DEFERRED_STRUCT_PAGE_INIT