5.15-stable review patch. If anyone has any objections, please let me know. ------------------ From: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx> [ Upstream commit ab3508854353793cd35e348fde89a5c09b2fd8b5 ] As there are more ALLOC_ flags that affect reserves, define what flags affect reserves and clarify the effect of each flag. Link: https://lkml.kernel.org/r/20230113111217.14134-5-mgorman@xxxxxxxxxxxxxxxxxxx Signed-off-by: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx> Acked-by: Vlastimil Babka <vbabka@xxxxxxx> Acked-by: Michal Hocko <mhocko@xxxxxxxx> Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx> Cc: NeilBrown <neilb@xxxxxxx> Cc: Thierry Reding <thierry.reding@xxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> Stable-dep-of: 281dd25c1a01 ("mm/page_alloc: let GFP_ATOMIC order-0 allocs access highatomic reserves") Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> --- mm/internal.h | 3 +++ mm/page_alloc.c | 34 ++++++++++++++++++++++------------ 2 files changed, 25 insertions(+), 12 deletions(-) diff --git a/mm/internal.h b/mm/internal.h index 136f435e0f1ab..717e75313693c 100644 --- a/mm/internal.h +++ b/mm/internal.h @@ -606,6 +606,9 @@ unsigned int reclaim_clean_pages_from_list(struct zone *zone, #define ALLOC_HIGHATOMIC 0x200 /* Allows access to MIGRATE_HIGHATOMIC */ #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) + enum ttu_flags; struct tlbflush_unmap_batch; diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 43122de999c4c..7778c2b11d8cb 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -3838,15 +3838,14 @@ ALLOW_ERROR_INJECTION(should_fail_alloc_page, TRUE); static inline long __zone_watermark_unusable_free(struct zone *z, unsigned int order, unsigned int alloc_flags) { - const bool alloc_harder = (alloc_flags & (ALLOC_HARDER|ALLOC_OOM)); long unusable_free = (1 << order) - 1; /* - * If the caller does not have rights to ALLOC_HARDER then subtract - * the high-atomic reserves. This will over-estimate the size of the - * atomic reserve but it avoids a search. + * If the caller does not have rights to reserves below the min + * watermark then subtract the high-atomic reserves. This will + * over-estimate the size of the atomic reserve but it avoids a search. */ - if (likely(!alloc_harder)) + if (likely(!(alloc_flags & ALLOC_RESERVES))) unusable_free += z->nr_reserved_highatomic; #ifdef CONFIG_CMA @@ -3870,25 +3869,36 @@ bool __zone_watermark_ok(struct zone *z, unsigned int order, unsigned long mark, { long min = mark; int o; - const bool alloc_harder = (alloc_flags & (ALLOC_HARDER|ALLOC_OOM)); /* free_pages may go negative - that's OK */ free_pages -= __zone_watermark_unusable_free(z, order, alloc_flags); - if (alloc_flags & ALLOC_MIN_RESERVE) - min -= min / 2; + if (unlikely(alloc_flags & ALLOC_RESERVES)) { + /* + * __GFP_HIGH allows access to 50% of the min reserve as well + * as OOM. + */ + if (alloc_flags & ALLOC_MIN_RESERVE) + min -= min / 2; - if (unlikely(alloc_harder)) { /* - * OOM victims can try even harder than normal ALLOC_HARDER + * 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; + + /* + * OOM victims can try even harder than the normal reserve * users on the grounds that it's definitely going to be in * the exit path shortly and free memory. Any allocation it * makes during the free path will be small and short-lived. */ if (alloc_flags & ALLOC_OOM) min -= min / 2; - else - min -= min / 4; } /* -- 2.43.0
