From: Mel Gorman Date: Fri, 24 Feb 2017 22:56:26 +0000 (-0800) Subject: mm, page_alloc: split buffered_rmqueue() X-Git-Tag: Ubuntu-5.0.0-8.9~5409^2~106 X-Git-Url: https://git.proxmox.com/?a=commitdiff_plain;h=066b23935578d3913c2df9bed7addbcdf4711f1a;p=mirror_ubuntu-disco-kernel.git mm, page_alloc: split buffered_rmqueue() Patch series "Use per-cpu allocator for !irq requests and prepare for a bulk allocator", v5. This series is motivated by a conversation led by Jesper Dangaard Brouer at the last LSF/MM proposing a generic page pool for DMA-coherent pages. Part of his motivation was due to the overhead of allocating multiple order-0 that led some drivers to use high-order allocations and splitting them. This is very slow in some cases. The first two patches in this series restructure the page allocator such that it is relatively easy to introduce an order-0 bulk page allocator. A patch exists to do that and has been handed over to Jesper until an in-kernel users is created. The third patch prevents the per-cpu allocator being drained from IPI context as that can potentially corrupt the list after patch four is merged. The final patch alters the per-cpu alloctor to make it exclusive to !irq requests. This cuts allocation/free overhead by roughly 30%. Performance tests from both Jesper and me are included in the patch. This patch (of 4): buffered_rmqueue removes a page from a given zone and uses the per-cpu list for order-0. This is fine but a hypothetical caller that wanted multiple order-0 pages has to disable/reenable interrupts multiple times. This patch structures buffere_rmqueue such that it's relatively easy to build a bulk order-0 page allocator. There is no functional change. [mgorman@techsingularity.net: failed per-cpu refill may blow up] Link: http://lkml.kernel.org/r/20170124112723.mshmgwq2ihxku2um@techsingularity.net Link: http://lkml.kernel.org/r/20170123153906.3122-2-mgorman@techsingularity.net Signed-off-by: Mel Gorman Acked-by: Hillf Danton Cc: Vlastimil Babka Cc: Jesper Dangaard Brouer Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- diff --git a/mm/page_alloc.c b/mm/page_alloc.c index c21b33668133..284153d3e0fc 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -2600,74 +2600,104 @@ static inline void zone_statistics(struct zone *preferred_zone, struct zone *z) #endif } +/* Remove page from the per-cpu list, caller must protect the list */ +static struct page *__rmqueue_pcplist(struct zone *zone, int migratetype, + bool cold, struct per_cpu_pages *pcp, + struct list_head *list) +{ + struct page *page; + + do { + if (list_empty(list)) { + pcp->count += rmqueue_bulk(zone, 0, + pcp->batch, list, + migratetype, cold); + if (unlikely(list_empty(list))) + return NULL; + } + + if (cold) + page = list_last_entry(list, struct page, lru); + else + page = list_first_entry(list, struct page, lru); + + list_del(&page->lru); + pcp->count--; + } while (check_new_pcp(page)); + + return page; +} + +/* Lock and remove page from the per-cpu list */ +static struct page *rmqueue_pcplist(struct zone *preferred_zone, + struct zone *zone, unsigned int order, + gfp_t gfp_flags, int migratetype) +{ + struct per_cpu_pages *pcp; + struct list_head *list; + bool cold = ((gfp_flags & __GFP_COLD) != 0); + struct page *page; + unsigned long flags; + + local_irq_save(flags); + pcp = &this_cpu_ptr(zone->pageset)->pcp; + list = &pcp->lists[migratetype]; + page = __rmqueue_pcplist(zone, migratetype, cold, pcp, list); + if (page) { + __count_zid_vm_events(PGALLOC, page_zonenum(page), 1 << order); + zone_statistics(preferred_zone, zone); + } + local_irq_restore(flags); + return page; +} + /* * Allocate a page from the given zone. Use pcplists for order-0 allocations. */ static inline -struct page *buffered_rmqueue(struct zone *preferred_zone, +struct page *rmqueue(struct zone *preferred_zone, struct zone *zone, unsigned int order, gfp_t gfp_flags, unsigned int alloc_flags, int migratetype) { unsigned long flags; struct page *page; - bool cold = ((gfp_flags & __GFP_COLD) != 0); if (likely(order == 0)) { - struct per_cpu_pages *pcp; - struct list_head *list; - - local_irq_save(flags); - do { - pcp = &this_cpu_ptr(zone->pageset)->pcp; - list = &pcp->lists[migratetype]; - if (list_empty(list)) { - pcp->count += rmqueue_bulk(zone, 0, - pcp->batch, list, - migratetype, cold); - if (unlikely(list_empty(list))) - goto failed; - } - - if (cold) - page = list_last_entry(list, struct page, lru); - else - page = list_first_entry(list, struct page, lru); - - list_del(&page->lru); - pcp->count--; + page = rmqueue_pcplist(preferred_zone, zone, order, + gfp_flags, migratetype); + goto out; + } - } while (check_new_pcp(page)); - } else { - /* - * We most definitely don't want callers attempting to - * allocate greater than order-1 page units with __GFP_NOFAIL. - */ - WARN_ON_ONCE((gfp_flags & __GFP_NOFAIL) && (order > 1)); - spin_lock_irqsave(&zone->lock, flags); + /* + * We most definitely don't want callers attempting to + * allocate greater than order-1 page units with __GFP_NOFAIL. + */ + WARN_ON_ONCE((gfp_flags & __GFP_NOFAIL) && (order > 1)); + spin_lock_irqsave(&zone->lock, flags); - do { - page = NULL; - if (alloc_flags & ALLOC_HARDER) { - page = __rmqueue_smallest(zone, order, MIGRATE_HIGHATOMIC); - if (page) - trace_mm_page_alloc_zone_locked(page, order, migratetype); - } - if (!page) - page = __rmqueue(zone, order, migratetype); - } while (page && check_new_pages(page, order)); - spin_unlock(&zone->lock); + do { + page = NULL; + if (alloc_flags & ALLOC_HARDER) { + page = __rmqueue_smallest(zone, order, MIGRATE_HIGHATOMIC); + if (page) + trace_mm_page_alloc_zone_locked(page, order, migratetype); + } if (!page) - goto failed; - __mod_zone_freepage_state(zone, -(1 << order), - get_pcppage_migratetype(page)); - } + page = __rmqueue(zone, order, migratetype); + } while (page && check_new_pages(page, order)); + spin_unlock(&zone->lock); + if (!page) + goto failed; + __mod_zone_freepage_state(zone, -(1 << order), + get_pcppage_migratetype(page)); __count_zid_vm_events(PGALLOC, page_zonenum(page), 1 << order); zone_statistics(preferred_zone, zone); local_irq_restore(flags); - VM_BUG_ON_PAGE(bad_range(zone, page), page); +out: + VM_BUG_ON_PAGE(page && bad_range(zone, page), page); return page; failed: @@ -2972,7 +3002,7 @@ get_page_from_freelist(gfp_t gfp_mask, unsigned int order, int alloc_flags, } try_this_zone: - page = buffered_rmqueue(ac->preferred_zoneref->zone, zone, order, + page = rmqueue(ac->preferred_zoneref->zone, zone, order, gfp_mask, alloc_flags, ac->migratetype); if (page) { prep_new_page(page, order, gfp_mask, alloc_flags);