| Message ID | 20230109151631.24923-4-mgorman@techsingularity.net (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | Discard __GFP_ATOMIC | expand |
On 1/9/23 16:16, Mel Gorman wrote: > A high-order ALLOC_HARDER allocation is assumed to be atomic. While that > is accurate, it changes later in the series. In preparation, explicitly > record high-order atomic allocations in gfp_to_alloc_flags(). There is > a slight functional change in that OOM handling avoids using high-order > reserve until it has to. > > Signed-off-by: Mel Gorman <mgorman@techsingularity.net> Acked-by: Vlastimil Babka <vbabka@suse.cz>
On Mon 09-01-23 15:16:27, Mel Gorman wrote: > A high-order ALLOC_HARDER allocation is assumed to be atomic. While that > is accurate, it changes later in the series. In preparation, explicitly > record high-order atomic allocations in gfp_to_alloc_flags(). There is > a slight functional change in that OOM handling avoids using high-order > reserve until it has to. I do not follow the oom handling part. IIRC we are dropping highatomic reserves before triggering oom. Something might have changed down the path but I can still see unreserve_highatomic_pageblock in should_reclaim_retry. I do not have any objection to ALLOC_HIGHATOMIC itself, though. > Signed-off-by: Mel Gorman <mgorman@techsingularity.net> > --- > mm/internal.h | 1 + > mm/page_alloc.c | 29 +++++++++++++++++++++++------ > 2 files changed, 24 insertions(+), 6 deletions(-) > > diff --git a/mm/internal.h b/mm/internal.h > index 403e4386626d..178484d9fd94 100644 > --- a/mm/internal.h > +++ b/mm/internal.h > @@ -746,6 +746,7 @@ unsigned int reclaim_clean_pages_from_list(struct zone *zone, > #else > #define ALLOC_NOFRAGMENT 0x0 > #endif > +#define ALLOC_HIGHATOMIC 0x200 /* Allows access to MIGRATE_HIGHATOMIC */ > #define ALLOC_KSWAPD 0x800 /* allow waking of kswapd, __GFP_KSWAPD_RECLAIM set */ > > enum ttu_flags; > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index 0040b4e00913..0ef4f3236a5a 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -3706,10 +3706,20 @@ struct page *rmqueue_buddy(struct zone *preferred_zone, struct zone *zone, > * reserved for high-order atomic allocation, so order-0 > * request should skip it. > */ > - if (order > 0 && alloc_flags & ALLOC_HARDER) > + if (alloc_flags & ALLOC_HIGHATOMIC) > page = __rmqueue_smallest(zone, order, MIGRATE_HIGHATOMIC); > if (!page) { > page = __rmqueue(zone, order, migratetype, alloc_flags); > + > + /* > + * If the allocation fails, allow OOM handling access > + * to HIGHATOMIC reserves as failing now is worse than > + * failing a high-order atomic allocation in the > + * future. > + */ > + if (!page && (alloc_flags & ALLOC_OOM)) > + page = __rmqueue_smallest(zone, order, MIGRATE_HIGHATOMIC); > + > if (!page) { > spin_unlock_irqrestore(&zone->lock, flags); > return NULL; > @@ -4023,8 +4033,10 @@ bool __zone_watermark_ok(struct zone *z, unsigned int order, unsigned long mark, > return true; > } > #endif > - if (alloc_harder && !free_area_empty(area, MIGRATE_HIGHATOMIC)) > + if ((alloc_flags & (ALLOC_HIGHATOMIC|ALLOC_OOM)) && > + !free_area_empty(area, MIGRATE_HIGHATOMIC)) { > return true; > + } > } > return false; > } > @@ -4286,7 +4298,7 @@ get_page_from_freelist(gfp_t gfp_mask, unsigned int order, int alloc_flags, > * If this is a high-order atomic allocation then check > * if the pageblock should be reserved for the future > */ > - if (unlikely(order && (alloc_flags & ALLOC_HARDER))) > + if (unlikely(alloc_flags & ALLOC_HIGHATOMIC)) > reserve_highatomic_pageblock(page, zone, order); > > return page; > @@ -4813,7 +4825,7 @@ static void wake_all_kswapds(unsigned int order, gfp_t gfp_mask, > } > > static inline unsigned int > -gfp_to_alloc_flags(gfp_t gfp_mask) > +gfp_to_alloc_flags(gfp_t gfp_mask, unsigned int order) > { > unsigned int alloc_flags = ALLOC_WMARK_MIN | ALLOC_CPUSET; > > @@ -4839,8 +4851,13 @@ gfp_to_alloc_flags(gfp_t gfp_mask) > * Not worth trying to allocate harder for __GFP_NOMEMALLOC even > * if it can't schedule. > */ > - if (!(gfp_mask & __GFP_NOMEMALLOC)) > + if (!(gfp_mask & __GFP_NOMEMALLOC)) { > alloc_flags |= ALLOC_HARDER; > + > + if (order > 0) > + alloc_flags |= ALLOC_HIGHATOMIC; > + } > + > /* > * Ignore cpuset mems for GFP_ATOMIC rather than fail, see the > * comment for __cpuset_node_allowed(). > @@ -5048,7 +5065,7 @@ __alloc_pages_slowpath(gfp_t gfp_mask, unsigned int order, > * kswapd needs to be woken up, and to avoid the cost of setting up > * alloc_flags precisely. So we do that now. > */ > - alloc_flags = gfp_to_alloc_flags(gfp_mask); > + alloc_flags = gfp_to_alloc_flags(gfp_mask, order); > > /* > * We need to recalculate the starting point for the zonelist iterator > -- > 2.35.3
On Wed, Jan 11, 2023 at 04:36:01PM +0100, Michal Hocko wrote: > On Mon 09-01-23 15:16:27, Mel Gorman wrote: > > A high-order ALLOC_HARDER allocation is assumed to be atomic. While that > > is accurate, it changes later in the series. In preparation, explicitly > > record high-order atomic allocations in gfp_to_alloc_flags(). There is > > a slight functional change in that OOM handling avoids using high-order > > reserve until it has to. > > I do not follow the oom handling part. IIRC we are dropping highatomic > reserves before triggering oom. Something might have changed down the > path but I can still see unreserve_highatomic_pageblock in > should_reclaim_retry. > That comment is now stale and should be removed because I fixed up the OOM oddities. At this point, a series resubmission is needed because a few changelogs have to be updated.
diff --git a/mm/internal.h b/mm/internal.h index 403e4386626d..178484d9fd94 100644 --- a/mm/internal.h +++ b/mm/internal.h @@ -746,6 +746,7 @@ unsigned int reclaim_clean_pages_from_list(struct zone *zone, #else #define ALLOC_NOFRAGMENT 0x0 #endif +#define ALLOC_HIGHATOMIC 0x200 /* Allows access to MIGRATE_HIGHATOMIC */ #define ALLOC_KSWAPD 0x800 /* allow waking of kswapd, __GFP_KSWAPD_RECLAIM set */ enum ttu_flags; diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 0040b4e00913..0ef4f3236a5a 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -3706,10 +3706,20 @@ struct page *rmqueue_buddy(struct zone *preferred_zone, struct zone *zone, * reserved for high-order atomic allocation, so order-0 * request should skip it. */ - if (order > 0 && alloc_flags & ALLOC_HARDER) + if (alloc_flags & ALLOC_HIGHATOMIC) page = __rmqueue_smallest(zone, order, MIGRATE_HIGHATOMIC); if (!page) { page = __rmqueue(zone, order, migratetype, alloc_flags); + + /* + * If the allocation fails, allow OOM handling access + * to HIGHATOMIC reserves as failing now is worse than + * failing a high-order atomic allocation in the + * future. + */ + if (!page && (alloc_flags & ALLOC_OOM)) + page = __rmqueue_smallest(zone, order, MIGRATE_HIGHATOMIC); + if (!page) { spin_unlock_irqrestore(&zone->lock, flags); return NULL; @@ -4023,8 +4033,10 @@ bool __zone_watermark_ok(struct zone *z, unsigned int order, unsigned long mark, return true; } #endif - if (alloc_harder && !free_area_empty(area, MIGRATE_HIGHATOMIC)) + if ((alloc_flags & (ALLOC_HIGHATOMIC|ALLOC_OOM)) && + !free_area_empty(area, MIGRATE_HIGHATOMIC)) { return true; + } } return false; } @@ -4286,7 +4298,7 @@ get_page_from_freelist(gfp_t gfp_mask, unsigned int order, int alloc_flags, * If this is a high-order atomic allocation then check * if the pageblock should be reserved for the future */ - if (unlikely(order && (alloc_flags & ALLOC_HARDER))) + if (unlikely(alloc_flags & ALLOC_HIGHATOMIC)) reserve_highatomic_pageblock(page, zone, order); return page; @@ -4813,7 +4825,7 @@ static void wake_all_kswapds(unsigned int order, gfp_t gfp_mask, } static inline unsigned int -gfp_to_alloc_flags(gfp_t gfp_mask) +gfp_to_alloc_flags(gfp_t gfp_mask, unsigned int order) { unsigned int alloc_flags = ALLOC_WMARK_MIN | ALLOC_CPUSET; @@ -4839,8 +4851,13 @@ gfp_to_alloc_flags(gfp_t gfp_mask) * Not worth trying to allocate harder for __GFP_NOMEMALLOC even * if it can't schedule. */ - if (!(gfp_mask & __GFP_NOMEMALLOC)) + if (!(gfp_mask & __GFP_NOMEMALLOC)) { alloc_flags |= ALLOC_HARDER; + + if (order > 0) + alloc_flags |= ALLOC_HIGHATOMIC; + } + /* * Ignore cpuset mems for GFP_ATOMIC rather than fail, see the * comment for __cpuset_node_allowed(). @@ -5048,7 +5065,7 @@ __alloc_pages_slowpath(gfp_t gfp_mask, unsigned int order, * kswapd needs to be woken up, and to avoid the cost of setting up * alloc_flags precisely. So we do that now. */ - alloc_flags = gfp_to_alloc_flags(gfp_mask); + alloc_flags = gfp_to_alloc_flags(gfp_mask, order); /* * We need to recalculate the starting point for the zonelist iterator
A high-order ALLOC_HARDER allocation is assumed to be atomic. While that is accurate, it changes later in the series. In preparation, explicitly record high-order atomic allocations in gfp_to_alloc_flags(). There is a slight functional change in that OOM handling avoids using high-order reserve until it has to. Signed-off-by: Mel Gorman <mgorman@techsingularity.net> --- mm/internal.h | 1 + mm/page_alloc.c | 29 +++++++++++++++++++++++------ 2 files changed, 24 insertions(+), 6 deletions(-)