The patch titled Subject: mm, meminit: recalculate pcpu batch and high limits after init completes has been removed from the -mm tree. Its filename was mm-meminit-recalculate-pcpu-batch-and-high-limits-after-init-completes.patch
This patch was dropped because an updated version will be merged
------------------------------------------------------ From: Mel Gorman mgorman@techsingularity.net Subject: mm, meminit: recalculate pcpu batch and high limits after init completes
Deferred memory initialisation updates zone->managed_pages during the initialisation phase but before that finishes, the per-cpu page allocator (pcpu) calculates the number of pages allocated/freed in batches as well as the maximum number of pages allowed on a per-cpu list. As zone->managed_pages is not up to date yet, the pcpu initialisation calculates inappropriately low batch and high values.
This increases zone lock contention quite severely in some cases with the degree of severity depending on how many CPUs share a local zone and the size of the zone. A private report indicated that kernel build times were excessive with extremely high system CPU usage. A perf profile indicated that a large chunk of time was lost on zone->lock contention.
This patch recalculates the pcpu batch and high values after deferred initialisation completes on each node. It was tested on a 2-socket AMD EPYC 2 machine using a kernel compilation workload -- allmodconfig and all available CPUs.
mmtests configuration: config-workload-kernbench-max Configuration was modified to build on a fresh XFS partition.
kernbench 5.4.0-rc3 5.4.0-rc3 vanilla resetpcpu-v1r1 Amean user-256 13249.50 ( 0.00%) 15928.40 * -20.22%* Amean syst-256 14760.30 ( 0.00%) 4551.77 * 69.16%* Amean elsp-256 162.42 ( 0.00%) 118.46 * 27.06%* Stddev user-256 42.97 ( 0.00%) 50.83 ( -18.30%) Stddev syst-256 336.87 ( 0.00%) 33.70 ( 90.00%) Stddev elsp-256 2.46 ( 0.00%) 0.81 ( 67.01%)
5.4.0-rc3 5.4.0-rc3 vanillaresetpcpu-v1r1 Duration User 39766.24 47802.92 Duration System 44298.10 13671.93 Duration Elapsed 519.11 387.65
The patch reduces system CPU usage by 69.16% and total build time by 27.06%. The variance of system CPU usage is also much reduced.
Link: http://lkml.kernel.org/r/20191018105606.3249-3-mgorman@techsingularity.net Signed-off-by: Mel Gorman mgorman@techsingularity.net Tested-by: Matt Fleming matt@codeblueprint.co.uk Acked-by: Michal Hocko mhocko@suse.com Cc: Vlastimil Babka vbabka@suse.cz Cc: Thomas Gleixner tglx@linutronix.de Cc: Borislav Petkov bp@alien8.de Cc: stable@vger.kernel.org [4.1+] Signed-off-by: Andrew Morton akpm@linux-foundation.org ---
mm/page_alloc.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-)
--- a/mm/page_alloc.c~mm-meminit-recalculate-pcpu-batch-and-high-limits-after-init-completes +++ a/mm/page_alloc.c @@ -1818,6 +1818,14 @@ static int __init deferred_init_memmap(v */ while (spfn < epfn) nr_pages += deferred_init_maxorder(&i, zone, &spfn, &epfn); + + /* + * The number of managed pages has changed due to the initialisation + * so the pcpu batch and high limits needs to be updated or the limits + * will be artificially small. + */ + zone_pcp_update(zone); + zone_empty: pgdat_resize_unlock(pgdat, &flags);
@@ -8514,7 +8522,6 @@ void free_contig_range(unsigned long pfn WARN(count != 0, "%d pages are still in use!\n", count); }
-#ifdef CONFIG_MEMORY_HOTPLUG /* * The zone indicated has a new number of managed_pages; batch sizes and percpu * page high values need to be recalulated. @@ -8528,7 +8535,6 @@ void __meminit zone_pcp_update(struct zo per_cpu_ptr(zone->pageset, cpu)); mutex_unlock(&pcp_batch_high_lock); } -#endif
void zone_pcp_reset(struct zone *zone) { _
Patches currently in -mm which might be from mgorman@techsingularity.net are
mm-pcp-share-common-code-between-memory-hotplug-and-percpu-sysctl-handler.patch mm-pcpu-make-zone-pcp-updates-and-reset-internal-to-the-mm.patch