diff options
| author | NeilBrown <neilb@suse.de> | 2023-01-13 11:12:17 +0000 |
|---|---|---|
| committer | Andrew Morton <akpm@linux-foundation.org> | 2023-02-02 22:33:13 -0800 |
| commit | 2973d8229b78d3f148e0c45916a1e8b237dc6167 (patch) | |
| tree | a791740a86d240df1cebf02f915e5aede7065ea4 /mm/page_alloc.c | |
| parent | 1ebbb21811b76c3b932959787f37985af36f62fa (diff) | |
mm: discard __GFP_ATOMIC
__GFP_ATOMIC serves little purpose. Its main effect is to set
ALLOC_HARDER which adds a few little boosts to increase the chance of an
allocation succeeding, one of which is to lower the water-mark at which it
will succeed.
It is *always* paired with __GFP_HIGH which sets ALLOC_HIGH which also
adjusts this watermark. It is probable that other users of __GFP_HIGH
should benefit from the other little bonuses that __GFP_ATOMIC gets.
__GFP_ATOMIC also gives a warning if used with __GFP_DIRECT_RECLAIM.
There is little point to this. We already get a might_sleep() warning if
__GFP_DIRECT_RECLAIM is set.
__GFP_ATOMIC allows the "watermark_boost" to be side-stepped. It is
probable that testing ALLOC_HARDER is a better fit here.
__GFP_ATOMIC is used by tegra-smmu.c to check if the allocation might
sleep. This should test __GFP_DIRECT_RECLAIM instead.
This patch:
- removes __GFP_ATOMIC
- allows __GFP_HIGH allocations to ignore watermark boosting as well
as GFP_ATOMIC requests.
- makes other adjustments as suggested by the above.
The net result is not change to GFP_ATOMIC allocations. Other
allocations that use __GFP_HIGH will benefit from a few different extra
privileges. This affects:
xen, dm, md, ntfs3
the vermillion frame buffer
hibernation
ksm
swap
all of which likely produce more benefit than cost if these selected
allocation are more likely to succeed quickly.
[mgorman: Minor adjustments to rework on top of a series]
Link: https://lkml.kernel.org/r/163712397076.13692.4727608274002939094@noble.neil.brown.name
Link: https://lkml.kernel.org/r/20230113111217.14134-7-mgorman@techsingularity.net
Signed-off-by: NeilBrown <neilb@suse.de>
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Thierry Reding <thierry.reding@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Diffstat (limited to 'mm/page_alloc.c')
| -rw-r--r-- | mm/page_alloc.c | 13 |
1 files changed, 3 insertions, 10 deletions
diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 18ca33a1945d..0cfad30fb44c 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -4105,13 +4105,14 @@ static inline bool zone_watermark_fast(struct zone *z, unsigned int order, if (__zone_watermark_ok(z, order, mark, highest_zoneidx, alloc_flags, free_pages)) return true; + /* - * Ignore watermark boosting for GFP_ATOMIC order-0 allocations + * Ignore watermark boosting for __GFP_HIGH 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 + if (unlikely(!order && (alloc_flags & ALLOC_MIN_RESERVE) && z->watermark_boost && ((alloc_flags & ALLOC_WMARK_MASK) == WMARK_MIN))) { mark = z->_watermark[WMARK_MIN]; return __zone_watermark_ok(z, order, mark, highest_zoneidx, @@ -5076,14 +5077,6 @@ __alloc_pages_slowpath(gfp_t gfp_mask, unsigned int order, unsigned int zonelist_iter_cookie; int reserve_flags; - /* - * We also sanity check to catch abuse of atomic reserves being used by - * callers that are not in atomic context. - */ - if (WARN_ON_ONCE((gfp_mask & (__GFP_ATOMIC|__GFP_DIRECT_RECLAIM)) == - (__GFP_ATOMIC|__GFP_DIRECT_RECLAIM))) - gfp_mask &= ~__GFP_ATOMIC; - restart: compaction_retries = 0; no_progress_loops = 0; |