From: Vlastimil Babka <vbabka@suse.cz>
To: Alex Shi <alex.shi@linux.alibaba.com>,
Mel Gorman <mgorman@techsingularity.net>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>,
David Hildenbrand <david@redhat.com>,
Matthew Wilcox <willy@infradead.org>,
Alexander Duyck <alexander.duyck@gmail.com>,
Andrew Morton <akpm@linux-foundation.org>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v4 1/4] mm/pageblock: mitigation cmpxchg false sharing in pageblock flags
Date: Thu, 3 Sep 2020 11:00:24 +0200 [thread overview]
Message-ID: <e4c95bf8-508a-3743-4547-1782938670a0@suse.cz> (raw)
In-Reply-To: <7813624a-d8af-f09f-d8c3-0d2a01fe5dd3@linux.alibaba.com>
On 9/3/20 10:40 AM, Alex Shi wrote:
>
>
> 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
The runs wildly differ in many of other stats, so I'm not sure they are really
comparable. I guess you could show the fraction of hit_cmpxchg to all cmpxchg.
But there's also danger of tracepoints widening the race window.
In the end what matters is how these 1208 retries contribute to runtime. I doubt
they could be really visible in a 100+ seconds run though.
next prev parent reply other threads:[~2020-09-03 9:00 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-03 7:01 Alex Shi
2020-09-03 7:01 ` [PATCH v4 2/4] mm/pageblock: remove false sharing in pageblock_flags Alex Shi
2020-09-03 7:01 ` [PATCH v4 3/4] mm/pageblock: work around multiple arch's cmpxchg support issue Alex Shi
2020-09-03 7:29 ` Max Filippov
2020-09-03 8:50 ` Alex Shi
2020-09-10 5:51 ` Christoph Hellwig
2020-09-03 7:24 ` [PATCH v4 1/4] mm/pageblock: mitigation cmpxchg false sharing in pageblock flags Mel Gorman
2020-09-03 8:32 ` Alex Shi
2020-09-03 8:40 ` Alex Shi
2020-09-03 9:00 ` Vlastimil Babka [this message]
2020-09-03 9:31 ` Mel Gorman
2020-09-03 8:19 ` David Hildenbrand
2020-09-03 9:14 ` Alex Shi
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