diff options
author | Huang Ying <ying.huang@intel.com> | 2023-10-16 13:29:56 +0800 |
---|---|---|
committer | Andrew Morton <akpm@linux-foundation.org> | 2023-10-25 16:47:10 -0700 |
commit | 362d37a106dd3f6431b2fdd91d9208b0d023b50d (patch) | |
tree | f51d1db4a765d1594fd34b62a96ca872d8e639da /mm/page_alloc.c | |
parent | 94a3bfe4073cd88b05f7fb201ea7bf9dfa2cf5d5 (diff) |
mm, pcp: reduce lock contention for draining high-order pages
In commit f26b3fa04611 ("mm/page_alloc: limit number of high-order pages
on PCP during bulk free"), the PCP (Per-CPU Pageset) will be drained when
PCP is mostly used for high-order pages freeing to improve the cache-hot
pages reusing between page allocating and freeing CPUs.
On system with small per-CPU data cache slice, pages shouldn't be cached
before draining to guarantee cache-hot. But on a system with large
per-CPU data cache slice, some pages can be cached before draining to
reduce zone lock contention.
So, in this patch, instead of draining without any caching, "pcp->batch"
pages will be cached in PCP before draining if the size of the per-CPU
data cache slice is more than "3 * batch".
In theory, if the size of per-CPU data cache slice is more than "2 *
batch", we can reuse cache-hot pages between CPUs. But considering the
other usage of cache (code, other data accessing, etc.), "3 * batch" is
used.
Note: "3 * batch" is chosen to make sure the optimization works on recent
x86_64 server CPUs. If you want to increase it, please check whether it
breaks the optimization.
On a 2-socket Intel server with 128 logical CPU, with the patch, the
network bandwidth of the UNIX (AF_UNIX) test case of lmbench test suite
with 16-pair processes increase 70.5%. The cycles% of the spinlock
contention (mostly for zone lock) decreases from 46.1% to 21.3%. The
number of PCP draining for high order pages freeing (free_high) decreases
89.9%. The cache miss rate keeps 0.2%.
Link: https://lkml.kernel.org/r/20231016053002.756205-4-ying.huang@intel.com
Signed-off-by: "Huang, Ying" <ying.huang@intel.com>
Acked-by: Mel Gorman <mgorman@techsingularity.net>
Cc: Sudeep Holla <sudeep.holla@arm.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: David Hildenbrand <david@redhat.com>
Cc: Johannes Weiner <jweiner@redhat.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Pavel Tatashin <pasha.tatashin@soleen.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Christoph Lameter <cl@linux.com>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Diffstat (limited to 'mm/page_alloc.c')
-rw-r--r-- | mm/page_alloc.c | 38 |
1 files changed, 37 insertions, 1 deletions
diff --git a/mm/page_alloc.c b/mm/page_alloc.c index de547ef9a9ad..b76b1de48a30 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -52,6 +52,7 @@ #include <linux/psi.h> #include <linux/khugepaged.h> #include <linux/delayacct.h> +#include <linux/cacheinfo.h> #include <asm/div64.h> #include "internal.h" #include "shuffle.h" @@ -2385,7 +2386,9 @@ static void free_unref_page_commit(struct zone *zone, struct per_cpu_pages *pcp, */ if (order && order <= PAGE_ALLOC_COSTLY_ORDER) { free_high = (pcp->free_factor && - (pcp->flags & PCPF_PREV_FREE_HIGH_ORDER)); + (pcp->flags & PCPF_PREV_FREE_HIGH_ORDER) && + (!(pcp->flags & PCPF_FREE_HIGH_BATCH) || + pcp->count >= READ_ONCE(pcp->batch))); pcp->flags |= PCPF_PREV_FREE_HIGH_ORDER; } else if (pcp->flags & PCPF_PREV_FREE_HIGH_ORDER) { pcp->flags &= ~PCPF_PREV_FREE_HIGH_ORDER; @@ -5418,6 +5421,39 @@ static void zone_pcp_update(struct zone *zone, int cpu_online) mutex_unlock(&pcp_batch_high_lock); } +static void zone_pcp_update_cacheinfo(struct zone *zone) +{ + int cpu; + struct per_cpu_pages *pcp; + struct cpu_cacheinfo *cci; + + for_each_online_cpu(cpu) { + pcp = per_cpu_ptr(zone->per_cpu_pageset, cpu); + cci = get_cpu_cacheinfo(cpu); + /* + * If data cache slice of CPU is large enough, "pcp->batch" + * pages can be preserved in PCP before draining PCP for + * consecutive high-order pages freeing without allocation. + * This can reduce zone lock contention without hurting + * cache-hot pages sharing. + */ + spin_lock(&pcp->lock); + if ((cci->per_cpu_data_slice_size >> PAGE_SHIFT) > 3 * pcp->batch) + pcp->flags |= PCPF_FREE_HIGH_BATCH; + else + pcp->flags &= ~PCPF_FREE_HIGH_BATCH; + spin_unlock(&pcp->lock); + } +} + +void setup_pcp_cacheinfo(void) +{ + struct zone *zone; + + for_each_populated_zone(zone) + zone_pcp_update_cacheinfo(zone); +} + /* * Allocate per cpu pagesets and initialize them. * Before this call only boot pagesets were available. |