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mm/page_alloc: explicitly define how __GFP_HIGH non-blocking allocations accesses reserves

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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>
This commit is contained in:
Mel Gorman 2023-01-13 11:12:16 +00:00 committed by Andrew Morton
parent ab35088543
commit 1ebbb21811
2 changed files with 29 additions and 22 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

7
mm/internal.h
View file

@ -778,7 +778,10 @@ unsigned int reclaim_clean_pages_from_list(struct zone *zone,
#define ALLOC_OOM ALLOC_NO_WATERMARKS #define ALLOC_OOM ALLOC_NO_WATERMARKS
#endif #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% #define ALLOC_MIN_RESERVE 0x20 /* __GFP_HIGH set. Allow access to 50%
* of the min watermark. * of the min watermark.
*/ */
@ -793,7 +796,7 @@ unsigned int reclaim_clean_pages_from_list(struct zone *zone,
#define ALLOC_KSWAPD 0x800 /* allow waking of kswapd, __GFP_KSWAPD_RECLAIM set */ #define ALLOC_KSWAPD 0x800 /* allow waking of kswapd, __GFP_KSWAPD_RECLAIM set */
/* Flags that allow allocations below the min watermark. */ /* 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; enum ttu_flags;
struct tlbflush_unmap_batch; struct tlbflush_unmap_batch;

44
mm/page_alloc.c
View file

@ -4007,18 +4007,19 @@ 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 * __GFP_HIGH allows access to 50% of the min reserve as well
* as OOM. * as OOM.
*/ */
if (alloc_flags & ALLOC_MIN_RESERVE) if (alloc_flags & ALLOC_MIN_RESERVE) {
min -= min / 2; min -= min / 2;
/* /*
* Non-blocking allocations can access some of the reserve * Non-blocking allocations (e.g. GFP_ATOMIC) can
* with more access if also __GFP_HIGH. The reasoning is that * access more reserves than just __GFP_HIGH. Other
* a non-blocking caller may incur a more severe penalty * non-blocking allocations requests such as GFP_NOWAIT
* if it cannot get memory quickly, particularly if it's * or (GFP_KERNEL & ~__GFP_DIRECT_RECLAIM) do not get
* also __GFP_HIGH. * access to the min reserve.
*/ */
if (alloc_flags & ALLOC_HARDER) if (alloc_flags & ALLOC_NON_BLOCK)
min -= min / 4; min -= min / 4;
}
/* /*
* OOM victims can try even harder than the normal reserve * OOM victims can try even harder than the normal reserve
@ -4869,28 +4870,30 @@ gfp_to_alloc_flags(gfp_t gfp_mask, unsigned int order)
* The caller may dip into page reserves a bit more if the caller * The caller may dip into page reserves a bit more if the caller
* cannot run direct reclaim, or if the caller has realtime scheduling * cannot run direct reclaim, or if the caller has realtime scheduling
* policy or is asking for __GFP_HIGH memory. GFP_ATOMIC requests will * 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) alloc_flags |= (__force int)
(gfp_mask & (__GFP_HIGH | __GFP_KSWAPD_RECLAIM)); (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 * Not worth trying to allocate harder for __GFP_NOMEMALLOC even
* if it can't schedule. * if it can't schedule.
*/ */
if (!(gfp_mask & __GFP_NOMEMALLOC)) { if (!(gfp_mask & __GFP_NOMEMALLOC)) {
alloc_flags |= ALLOC_HARDER; alloc_flags |= ALLOC_NON_BLOCK;
if (order > 0) if (order > 0)
alloc_flags |= ALLOC_HIGHATOMIC; alloc_flags |= ALLOC_HIGHATOMIC;
} }
/* /*
* Ignore cpuset mems for GFP_ATOMIC rather than fail, see the * Ignore cpuset mems for non-blocking __GFP_HIGH (probably
* comment for __cpuset_node_allowed(). * 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()) } else if (unlikely(rt_task(current)) && in_task())
alloc_flags |= ALLOC_MIN_RESERVE; alloc_flags |= ALLOC_MIN_RESERVE;
@ -5321,12 +5324,13 @@ __alloc_pages_slowpath(gfp_t gfp_mask, unsigned int order,
WARN_ON_ONCE_GFP(costly_order, gfp_mask); WARN_ON_ONCE_GFP(costly_order, gfp_mask);
/* /*
* Help non-failing allocations by giving them access to memory * Help non-failing allocations by giving some access to memory
* reserves but do not use ALLOC_NO_WATERMARKS because this * 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 * 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) if (page)
goto got_pg; goto got_pg;