| Message ID | 20230109151631.24923-5-mgorman@techsingularity.net (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | Discard __GFP_ATOMIC | expand |
On 1/9/23 16:16, Mel Gorman wrote: > As there are more ALLOC_ flags that affect reserves, define what flags > affect reserves and clarify the effect of each flag. > > Signed-off-by: Mel Gorman <mgorman@techsingularity.net> Acked-by: Vlastimil Babka <vbabka@suse.cz>
On Mon 09-01-23 15:16:28, Mel Gorman wrote: > As there are more ALLOC_ flags that affect reserves, define what flags > affect reserves and clarify the effect of each flag. I like this! It makes the code much easier to follow. > Signed-off-by: Mel Gorman <mgorman@techsingularity.net> Acked-by: Michal Hocko <mhocko@suse.com> Thanks! > --- > 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 178484d9fd94..8706d46863df 100644 > --- a/mm/internal.h > +++ b/mm/internal.h > @@ -749,6 +749,9 @@ 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 0ef4f3236a5a..6f41b84a97ac 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -3949,15 +3949,14 @@ 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 > @@ -3981,25 +3980,36 @@ 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; > } > > /* > -- > 2.35.3
diff --git a/mm/internal.h b/mm/internal.h index 178484d9fd94..8706d46863df 100644 --- a/mm/internal.h +++ b/mm/internal.h @@ -749,6 +749,9 @@ 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 0ef4f3236a5a..6f41b84a97ac 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -3949,15 +3949,14 @@ 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 @@ -3981,25 +3980,36 @@ 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; } /*
As there are more ALLOC_ flags that affect reserves, define what flags affect reserves and clarify the effect of each flag. Signed-off-by: Mel Gorman <mgorman@techsingularity.net> --- mm/internal.h | 3 +++ mm/page_alloc.c | 34 ++++++++++++++++++++++------------ 2 files changed, 25 insertions(+), 12 deletions(-)