5.15-stable review patch. If anyone has any objections, please let me know.
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From: Mel Gorman mgorman@techsingularity.net
[ Upstream commit 1ebbb21811b76c3b932959787f37985af36f62fa ]
GFP_ATOMIC allocations get flagged ALLOC_HARDER which is a vague description. In preparation for the removal of GFP_ATOMIC redefine __GFP_ATOMIC to simply mean non-blocking and renaming ALLOC_HARDER to ALLOC_NON_BLOCK accordingly. __GFP_HIGH is required for access to reserves but non-blocking is granted more access. For example, GFP_NOWAIT is non-blocking but has no special access to reserves. A __GFP_NOFAIL blocking allocation is granted access similar to __GFP_HIGH if the only alternative is an OOM kill.
Link: https://lkml.kernel.org/r/20230113111217.14134-6-mgorman@techsingularity.net Signed-off-by: Mel Gorman mgorman@techsingularity.net Acked-by: Michal Hocko mhocko@suse.com Cc: Matthew Wilcox willy@infradead.org Cc: NeilBrown neilb@suse.de Cc: Thierry Reding thierry.reding@gmail.com Cc: Vlastimil Babka vbabka@suse.cz Signed-off-by: Andrew Morton akpm@linux-foundation.org Stable-dep-of: 281dd25c1a01 ("mm/page_alloc: let GFP_ATOMIC order-0 allocs access highatomic reserves") Signed-off-by: Sasha Levin sashal@kernel.org --- mm/internal.h | 7 +++++-- mm/page_alloc.c | 44 ++++++++++++++++++++++++-------------------- 2 files changed, 29 insertions(+), 22 deletions(-)
diff --git a/mm/internal.h b/mm/internal.h index 717e75313693c..cd444aa7a10af 100644 --- a/mm/internal.h +++ b/mm/internal.h @@ -592,7 +592,10 @@ unsigned int reclaim_clean_pages_from_list(struct zone *zone, #define ALLOC_OOM ALLOC_NO_WATERMARKS #endif
-#define ALLOC_HARDER 0x10 /* try to alloc harder */ +#define ALLOC_NON_BLOCK 0x10 /* Caller cannot block. Allow access + * to 25% of the min watermark or + * 62.5% if __GFP_HIGH is set. + */ #define ALLOC_MIN_RESERVE 0x20 /* __GFP_HIGH set. Allow access to 50% * of the min watermark. */ @@ -607,7 +610,7 @@ unsigned int reclaim_clean_pages_from_list(struct zone *zone, #define ALLOC_KSWAPD 0x800 /* allow waking of kswapd, __GFP_KSWAPD_RECLAIM set */
/* Flags that allow allocations below the min watermark. */ -#define ALLOC_RESERVES (ALLOC_HARDER|ALLOC_MIN_RESERVE|ALLOC_HIGHATOMIC|ALLOC_OOM) +#define ALLOC_RESERVES (ALLOC_NON_BLOCK|ALLOC_MIN_RESERVE|ALLOC_HIGHATOMIC|ALLOC_OOM)
enum ttu_flags; struct tlbflush_unmap_batch; diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 7778c2b11d8cb..404cee30dcc26 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -3878,18 +3878,19 @@ bool __zone_watermark_ok(struct zone *z, unsigned int order, unsigned long mark, * __GFP_HIGH allows access to 50% of the min reserve as well * as OOM. */ - if (alloc_flags & ALLOC_MIN_RESERVE) + if (alloc_flags & ALLOC_MIN_RESERVE) { min -= min / 2;
- /* - * Non-blocking allocations can access some of the reserve - * with more access if also __GFP_HIGH. The reasoning is that - * a non-blocking caller may incur a more severe penalty - * if it cannot get memory quickly, particularly if it's - * also __GFP_HIGH. - */ - if (alloc_flags & ALLOC_HARDER) - min -= min / 4; + /* + * Non-blocking allocations (e.g. GFP_ATOMIC) can + * access more reserves than just __GFP_HIGH. Other + * non-blocking allocations requests such as GFP_NOWAIT + * or (GFP_KERNEL & ~__GFP_DIRECT_RECLAIM) do not get + * access to the min reserve. + */ + if (alloc_flags & ALLOC_NON_BLOCK) + min -= min / 4; + }
/* * OOM victims can try even harder than the normal reserve @@ -4729,28 +4730,30 @@ gfp_to_alloc_flags(gfp_t gfp_mask, unsigned int order) * 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 (__GFP_ATOMIC) and ALLOC_MIN_RESERVE(__GFP_HIGH). + * set both ALLOC_NON_BLOCK and ALLOC_MIN_RESERVE(__GFP_HIGH). */ alloc_flags |= (__force int) (gfp_mask & (__GFP_HIGH | __GFP_KSWAPD_RECLAIM));
- if (gfp_mask & __GFP_ATOMIC) { + if (!(gfp_mask & __GFP_DIRECT_RECLAIM)) { /* * Not worth trying to allocate harder for __GFP_NOMEMALLOC even * if it can't schedule. */ if (!(gfp_mask & __GFP_NOMEMALLOC)) { - alloc_flags |= ALLOC_HARDER; + alloc_flags |= ALLOC_NON_BLOCK;
if (order > 0) alloc_flags |= ALLOC_HIGHATOMIC; }
/* - * Ignore cpuset mems for GFP_ATOMIC rather than fail, see the - * comment for __cpuset_node_allowed(). + * Ignore cpuset mems for non-blocking __GFP_HIGH (probably + * GFP_ATOMIC) rather than fail, see the comment for + * __cpuset_node_allowed(). */ - alloc_flags &= ~ALLOC_CPUSET; + if (alloc_flags & ALLOC_MIN_RESERVE) + alloc_flags &= ~ALLOC_CPUSET; } else if (unlikely(rt_task(current)) && in_task()) alloc_flags |= ALLOC_MIN_RESERVE;
@@ -5188,12 +5191,13 @@ __alloc_pages_slowpath(gfp_t gfp_mask, unsigned int order, WARN_ON_ONCE(order > PAGE_ALLOC_COSTLY_ORDER);
/* - * Help non-failing allocations by giving them access to memory - * reserves but do not use ALLOC_NO_WATERMARKS because this + * Help non-failing allocations by giving some access to memory + * reserves normally used for high priority non-blocking + * allocations but do not use ALLOC_NO_WATERMARKS because this * could deplete whole memory reserves which would just make - * the situation worse + * the situation worse. */ - page = __alloc_pages_cpuset_fallback(gfp_mask, order, ALLOC_HARDER, ac); + page = __alloc_pages_cpuset_fallback(gfp_mask, order, ALLOC_MIN_RESERVE, ac); if (page) goto got_pg;