Commit 5d0a661d authored by Mel Gorman's avatar Mel Gorman Committed by Andrew Morton
Browse files

mm/page_alloc: use only one PCP list for THP-sized allocations 

The per_cpu_pages is cache-aligned on a standard x86-64 distribution
configuration but a later patch will add a new field which would push the
structure into the next cache line.  Use only one list to store THP-sized
pages on the per-cpu list.  This assumes that the vast majority of
THP-sized allocations are GFP_MOVABLE but even if it was another type, it
would not contribute to serious fragmentation that potentially causes a
later THP allocation failure.  Align per_cpu_pages on the cacheline
boundary to ensure there is no false cache sharing.

After this patch, the structure sizing is;

struct per_cpu_pages {
        int                        count;                /*     0     4 */
        int                        high;                 /*     4     4 */
        int                        batch;                /*     8     4 */
        short int                  free_factor;          /*    12     2 */
        short int                  expire;               /*    14     2 */
        struct list_head           lists[13];            /*    16   208 */

        /* size: 256, cachelines: 4, members: 6 */
        /* padding: 32 */
} __attribute__((__aligned__(64)));

Link: https://lkml.kernel.org/r/20220624125423.6126-3-mgorman@techsingularity.net


Signed-off-by: default avatarMel Gorman <mgorman@techsingularity.net>
Tested-by: default avatarMinchan Kim <minchan@kernel.org>
Acked-by: default avatarMinchan Kim <minchan@kernel.org>
Acked-by: default avatarVlastimil Babka <vbabka@suse.cz>
Tested-by: default avatarYu Zhao <yuzhao@google.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Marcelo Tosatti <mtosatti@redhat.com>
Cc: Marek Szyprowski <m.szyprowski@samsung.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Nicolas Saenz Julienne <nsaenzju@redhat.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent bf75f200

include/linux/mmzone.h

+7 −4
Original line number Diff line number Diff line
@@ -355,15 +355,18 @@ enum zone_watermarks { 
};



/*

 * One per migratetype for each PAGE_ALLOC_COSTLY_ORDER plus one additional

 * for pageblock size for THP if configured.

 * One per migratetype for each PAGE_ALLOC_COSTLY_ORDER. One additional list

 * for THP which will usually be GFP_MOVABLE. Even if it is another type,

 * it should not contribute to serious fragmentation causing THP allocation

 * failures.

 */

#ifdef CONFIG_TRANSPARENT_HUGEPAGE

#define NR_PCP_THP 1

#else

#define NR_PCP_THP 0

#endif

#define NR_PCP_LISTS (MIGRATE_PCPTYPES * (PAGE_ALLOC_COSTLY_ORDER + 1 + NR_PCP_THP))

#define NR_LOWORDER_PCP_LISTS (MIGRATE_PCPTYPES * (PAGE_ALLOC_COSTLY_ORDER + 1))

#define NR_PCP_LISTS (NR_LOWORDER_PCP_LISTS + NR_PCP_THP)



/*

 * Shift to encode migratetype and order in the same integer, with order
@@ -389,7 +392,7 @@ struct per_cpu_pages { 


	/* Lists of pages, one per migrate type stored on the pcp-lists */

	struct list_head lists[NR_PCP_LISTS];

};

} ____cacheline_aligned_in_smp;



struct per_cpu_zonestat {

#ifdef CONFIG_SMP

mm/page_alloc.c

+2 −2
Original line number Diff line number Diff line
@@ -653,7 +653,7 @@ static inline unsigned int order_to_pindex(int migratetype, int order) 
#ifdef CONFIG_TRANSPARENT_HUGEPAGE

	if (order > PAGE_ALLOC_COSTLY_ORDER) {

		VM_BUG_ON(order != pageblock_order);

		base = PAGE_ALLOC_COSTLY_ORDER + 1;

		return NR_LOWORDER_PCP_LISTS;

	}

#else

	VM_BUG_ON(order > PAGE_ALLOC_COSTLY_ORDER);
@@ -667,7 +667,7 @@ static inline int pindex_to_order(unsigned int pindex) 
	int order = pindex / MIGRATE_PCPTYPES;



#ifdef CONFIG_TRANSPARENT_HUGEPAGE

	if (order > PAGE_ALLOC_COSTLY_ORDER)

	if (pindex == NR_LOWORDER_PCP_LISTS)

		order = pageblock_order;

#else

	VM_BUG_ON(order > PAGE_ALLOC_COSTLY_ORDER);