From: David Hildenbrand <david@redhat.com>
To: Alex Shi <alex.shi@linux.alibaba.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Hugh Dickins <hughd@google.com>,
Alexander Duyck <alexander.h.duyck@linux.intel.com>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/2] mm/pageblock: mitigation cmpxchg false sharing in pageblock flags
Date: Sun, 16 Aug 2020 14:16:07 +0200 [thread overview]
Message-ID: <eeb80957-96f7-661c-1510-0e6247570bd3@redhat.com> (raw)
In-Reply-To: <1597549677-7480-1-git-send-email-alex.shi@linux.alibaba.com>
On 16.08.20 05:47, Alex Shi wrote:
> pageblock_flags is used as long, since every pageblock_flags is just 4
> bits, 'long' size will include 8(32bit machine) or 16 pageblocks' flags,
> that flag setting has to sync in cmpxchg with 7 or 15 other pageblock
> flags. It would cause long waiting for sync.
>
> If we could change the pageblock_flags variable as char, we could use
> char size cmpxchg, which just sync up with 2 pageblock flags. it could
> relief much false sharing in cmpxchg.
Do you have any performance numbers to back your claims? IOW, do we care
at all?
--
Thanks,
David / dhildenb
next prev parent reply other threads:[~2020-08-16 12:16 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-08-16 3:47 [PATCH 1/2] mm/pageblock: mitigation cmpxchg false sharing in pageblock flags Alex Shi
2020-08-16 3:47 ` [PATCH 2/2] mm/pageblock: remove false sharing in pageblock_flags Alex Shi
2020-08-16 4:17 ` Matthew Wilcox
2020-08-16 14:10 ` Alex Shi
2020-08-16 15:56 ` Alexander Duyck
2020-08-18 7:15 ` Alex Shi
2020-08-16 4:09 ` [PATCH 1/2] mm/pageblock: mitigation cmpxchg false sharing in pageblock flags Matthew Wilcox
2020-08-16 13:53 ` Alex Shi
2020-08-16 12:16 ` David Hildenbrand [this message]
2020-08-16 14:14 ` Alex Shi
2020-08-17 9:58 ` Wei Yang
2020-08-17 11:02 ` Alex Shi
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