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Subject: Re: [PATCH v4 1/4] mm/pageblock: mitigation cmpxchg false sharing in
 pageblock flags
From:   Alex Shi <alex.shi@linux.alibaba.com>
To:     Mel Gorman <mgorman@techsingularity.net>
Cc:     Anshuman Khandual <anshuman.khandual@arm.com>,
        David Hildenbrand <david@redhat.com>,
        Matthew Wilcox <willy@infradead.org>,
        Vlastimil Babka <vbabka@suse.cz>,
        Alexander Duyck <alexander.duyck@gmail.com>,
        Andrew Morton <akpm@linux-foundation.org>, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org
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Date:   Thu, 3 Sep 2020 16:40:40 +0800
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在 2020/9/3 下午4:32, Alex Shi 写道:
>>
> I have run thpscale with 'always' defrag setting of THP. The Amean stddev is much
> larger than a very little average run time reducing.
> 
> But the left patch 4 could show the cmpxchg retry reduce from thousands to hundreds
> or less.
> 
> Subject: [PATCH v4 4/4] add cmpxchg tracing


It's a typical result with the patchset:

 Performance counter stats for './run-mmtests.sh -c configs/config-workload-thpscale pageblock-c':

             9,564      compaction:mm_compaction_isolate_migratepages
             6,430      compaction:mm_compaction_isolate_freepages
             5,287      compaction:mm_compaction_migratepages
            45,299      compaction:mm_compaction_begin
            45,299      compaction:mm_compaction_end
            30,557      compaction:mm_compaction_try_to_compact_pages
            95,540      compaction:mm_compaction_finished
           149,379      compaction:mm_compaction_suitable
                 0      compaction:mm_compaction_deferred
                 0      compaction:mm_compaction_defer_compaction
             3,949      compaction:mm_compaction_defer_reset
                 0      compaction:mm_compaction_kcompactd_sleep
                 0      compaction:mm_compaction_wakeup_kcompactd
                 0      compaction:mm_compaction_kcompactd_wake
                68      pageblock:hit_cmpxchg

     113.570974583 seconds time elapsed

      14.664451000 seconds user
      96.847116000 seconds sys

It's 5.9-rc2 base kernel result:

 Performance counter stats for './run-mmtests.sh -c configs/config-workload-thpscale rc2-e':

            15,920      compaction:mm_compaction_isolate_migratepages
            20,523      compaction:mm_compaction_isolate_freepages
             9,752      compaction:mm_compaction_migratepages
            27,773      compaction:mm_compaction_begin
            27,773      compaction:mm_compaction_end
            16,391      compaction:mm_compaction_try_to_compact_pages
            62,809      compaction:mm_compaction_finished
            69,821      compaction:mm_compaction_suitable
                 0      compaction:mm_compaction_deferred
                 0      compaction:mm_compaction_defer_compaction
             7,875      compaction:mm_compaction_defer_reset
                 0      compaction:mm_compaction_kcompactd_sleep
                 0      compaction:mm_compaction_wakeup_kcompactd
                 0      compaction:mm_compaction_kcompactd_wake
             1,208      pageblock:hit_cmpxchg

     116.440414591 seconds time elapsed

      15.326913000 seconds user
     103.752758000 seconds sys