All of lore.kernel.org
 help / color / mirror / Atom feed
From: Wei Yang <richard.weiyang@linux.alibaba.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: Mon, 17 Aug 2020 17:58:21 +0800	[thread overview]
Message-ID: <20200817095821.GA29756@L-31X9LVDL-1304.local> (raw)
In-Reply-To: <1597549677-7480-1-git-send-email-alex.shi@linux.alibaba.com>

On Sun, Aug 16, 2020 at 11:47:56AM +0800, 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.
>

If my understanding is correct, CPU reads data in the size of cacheline.
Define a variable a char or other, doesn't help on false sharing. 

Correct me, if not.

-- 
Wei Yang
Help you, Help me

  parent reply	other threads:[~2020-08-17  9:58 UTC|newest]

Thread overview: 15+ 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 ` Alex Shi
2020-08-16  3:47 ` [PATCH 2/2] mm/pageblock: remove false sharing in pageblock_flags Alex Shi
2020-08-16  3:47   ` Alex Shi
2020-08-16  4:17   ` Matthew Wilcox
2020-08-16 14:10     ` Alex Shi
2020-08-16 15:56       ` Alexander Duyck
2020-08-16 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
2020-08-16 14:14   ` Alex Shi
2020-08-17  9:58 ` Wei Yang [this message]
2020-08-17 11:02   ` Alex Shi

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20200817095821.GA29756@L-31X9LVDL-1304.local \
    --to=richard.weiyang@linux.alibaba.com \
    --cc=akpm@linux-foundation.org \
    --cc=alex.shi@linux.alibaba.com \
    --cc=alexander.h.duyck@linux.intel.com \
    --cc=hughd@google.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-mm@kvack.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.