On Wed 15-07-20 14:05:26, Joonsoo Kim wrote:
From: Joonsoo Kim iamjoonsoo.kim@lge.com
Currently, preventing cma area in page allocation is implemented by using current_gfp_context(). However, there are two problems of this implementation.
First, this doesn't work for allocation fastpath. In the fastpath, original gfp_mask is used since current_gfp_context() is introduced in order to control reclaim and it is on slowpath. Second, clearing __GFP_MOVABLE has a side effect to exclude the memory on the ZONE_MOVABLE for allocation target.
This can be especially a problem with movable_node configurations where a large portion of the memory is in movable zones.
To fix these problems, this patch changes the implementation to exclude cma area in page allocation. Main point of this change is using the alloc_flags. alloc_flags is mainly used to control allocation so it fits for excluding cma area in allocation.
The approach is sensible and the patch makes sense to me from a quick glance but I am not really familiar with all subtle details about cma integration with the allocator so I do not feel confident to provide my ack.
Thanks!
Fixes: d7fefcc (mm/cma: add PF flag to force non cma alloc) Cc: stable@vger.kernel.org Signed-off-by: Joonsoo Kim iamjoonsoo.kim@lge.com
include/linux/sched/mm.h | 4 ---- mm/page_alloc.c | 27 +++++++++++++++------------ 2 files changed, 15 insertions(+), 16 deletions(-)
diff --git a/include/linux/sched/mm.h b/include/linux/sched/mm.h index 44ad5b7..a73847a 100644 --- a/include/linux/sched/mm.h +++ b/include/linux/sched/mm.h @@ -191,10 +191,6 @@ static inline gfp_t current_gfp_context(gfp_t flags) flags &= ~(__GFP_IO | __GFP_FS); else if (pflags & PF_MEMALLOC_NOFS) flags &= ~__GFP_FS; -#ifdef CONFIG_CMA
if (pflags & PF_MEMALLOC_NOCMA)flags &= ~__GFP_MOVABLE;-#endif } return flags; } diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 6416d08..cd53894 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -2791,7 +2791,7 @@ __rmqueue(struct zone *zone, unsigned int order, int migratetype, * allocating from CMA when over half of the zone's free memory * is in the CMA area. */
- if (migratetype == MIGRATE_MOVABLE &&
- if (alloc_flags & ALLOC_CMA && zone_page_state(zone, NR_FREE_CMA_PAGES) > zone_page_state(zone, NR_FREE_PAGES) / 2) { page = __rmqueue_cma_fallback(zone, order);
@@ -2802,7 +2802,7 @@ __rmqueue(struct zone *zone, unsigned int order, int migratetype, retry: page = __rmqueue_smallest(zone, order, migratetype); if (unlikely(!page)) {
if (migratetype == MIGRATE_MOVABLE)
if (alloc_flags & ALLOC_CMA) page = __rmqueue_cma_fallback(zone, order);if (!page && __rmqueue_fallback(zone, order, migratetype, @@ -3502,11 +3502,9 @@ static inline long __zone_watermark_unusable_free(struct zone *z, if (likely(!alloc_harder)) unusable_free += z->nr_reserved_highatomic; -#ifdef CONFIG_CMA /* If allocation can't use CMA areas don't use free CMA pages */
- if (!(alloc_flags & ALLOC_CMA))
- if (IS_ENABLED(CONFIG_CMA) && !(alloc_flags & ALLOC_CMA)) unusable_free += zone_page_state(z, NR_FREE_CMA_PAGES);
-#endif return unusable_free; } @@ -3693,6 +3691,16 @@ alloc_flags_nofragment(struct zone *zone, gfp_t gfp_mask) return alloc_flags; } +static inline void current_alloc_flags(gfp_t gfp_mask,
unsigned int *alloc_flags)+{
- unsigned int pflags = READ_ONCE(current->flags);
- if (!(pflags & PF_MEMALLOC_NOCMA) &&
gfp_migratetype(gfp_mask) == MIGRATE_MOVABLE)*alloc_flags |= ALLOC_CMA;+}
/*
- get_page_from_freelist goes through the zonelist trying to allocate
- a page.
@@ -3706,6 +3714,8 @@ get_page_from_freelist(gfp_t gfp_mask, unsigned int order, int alloc_flags, struct pglist_data *last_pgdat_dirty_limit = NULL; bool no_fallback;
- current_alloc_flags(gfp_mask, &alloc_flags);
retry: /* * Scan zonelist, looking for a zone with enough free. @@ -4339,10 +4349,6 @@ gfp_to_alloc_flags(gfp_t gfp_mask) } else if (unlikely(rt_task(current)) && !in_interrupt()) alloc_flags |= ALLOC_HARDER; -#ifdef CONFIG_CMA
- if (gfp_migratetype(gfp_mask) == MIGRATE_MOVABLE)
alloc_flags |= ALLOC_CMA;-#endif return alloc_flags; } @@ -4808,9 +4814,6 @@ static inline bool prepare_alloc_pages(gfp_t gfp_mask, unsigned int order, if (should_fail_alloc_page(gfp_mask, order)) return false;
- if (IS_ENABLED(CONFIG_CMA) && ac->migratetype == MIGRATE_MOVABLE)
*alloc_flags |= ALLOC_CMA;- return true;
} -- 2.7.4