From: Michal Hocko <mhocko@suse.cz>
To: Sha Zhengju <handai.szj@gmail.com>
Cc: cgroups@vger.kernel.org, linux-mm@kvack.org,
kamezawa.hiroyu@jp.fujitsu.com, akpm@linux-foundation.org,
hughd@google.com, gthelen@google.com,
Sha Zhengju <handai.szj@taobao.com>
Subject: Re: [PATCH V2 2/3] memcg: alter mem_cgroup_{update,inc,dec}_page_stat() args to memcg pointer
Date: Mon, 13 May 2013 14:25:04 +0200 [thread overview]
Message-ID: <20130513122504.GA5246@dhcp22.suse.cz> (raw)
In-Reply-To: <1368421524-4937-1-git-send-email-handai.szj@taobao.com>
On Mon 13-05-13 13:05:24, Sha Zhengju wrote:
> From: Sha Zhengju <handai.szj@taobao.com>
>
> Change the first argument of mem_cgroup_{update,inc,dec}_page_stat() from
> 'struct page *' to 'struct mem_cgroup *', and so move PageCgroupUsed(pc)
> checking out of mem_cgroup_update_page_stat(). This is a prepare patch for
> the following memcg page stat lock simplifying.
No, please do not do this because it just spreads memcg specific code
out of memcontrol.c. Besides that the patch is not correct.
[...]
> --- a/mm/rmap.c
> +++ b/mm/rmap.c
> @@ -1109,12 +1109,24 @@ void page_add_file_rmap(struct page *page)
> {
> bool locked;
> unsigned long flags;
> + struct page_cgroup *pc;
> + struct mem_cgroup *memcg = NULL;
>
> mem_cgroup_begin_update_page_stat(page, &locked, &flags);
> + pc = lookup_page_cgroup(page);
> +
> + rcu_read_lock();
> + memcg = pc->mem_cgroup;
a) unnecessary RCU take for memcg disabled and b) worse KABOOM in that case
as page_cgroup is NULL. We really do not want to put
mem_cgroup_disabled() tests all over the place. The idea behind
mem_cgroup_begin_update_page_stat was to be almost a noop for !memcg
(and the real noop for !CONFIG_MEMCG).
so Nak to this approach
--
Michal Hocko
SUSE Labs
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org. For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
next prev parent reply other threads:[~2013-05-13 12:25 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-05-13 5:03 [PATCH V2 0/3] memcg: simply lock of page stat accounting Sha Zhengju
2013-05-13 5:04 ` [PATCH V2 1/3] memcg: rewrite the comment about race condition " Sha Zhengju
2013-05-13 5:05 ` [PATCH V2 2/3] memcg: alter mem_cgroup_{update,inc,dec}_page_stat() args to memcg pointer Sha Zhengju
2013-05-13 12:25 ` Michal Hocko [this message]
2013-05-14 9:00 ` Sha Zhengju
2013-05-14 9:10 ` Michal Hocko
2013-05-14 0:15 ` Kamezawa Hiroyuki
2013-05-14 9:03 ` Sha Zhengju
2013-05-13 5:05 ` [PATCH V2 3/3] memcg: simplify lock of memcg page stat account Sha Zhengju
2013-05-13 13:12 ` Michal Hocko
2013-05-13 13:38 ` Michal Hocko
2013-05-14 9:13 ` Sha Zhengju
2013-05-14 9:28 ` Michal Hocko
2013-05-14 8:35 ` Sha Zhengju
2013-05-14 0:41 ` [PATCH V2 0/3] memcg: simply lock of page stat accounting Kamezawa Hiroyuki
2013-05-14 7:13 ` Michal Hocko
2013-05-15 12:35 ` Konstantin Khlebnikov
2013-05-15 13:41 ` Michal Hocko
2013-05-16 4:28 ` Konstantin Khlebnikov
2013-05-16 13:28 ` Michal Hocko
2013-05-17 5:57 ` Konstantin Khlebnikov
2013-05-17 8:38 ` Michal Hocko
2013-05-17 10:29 ` Konstantin Khlebnikov
2013-05-17 12:53 ` Michal Hocko
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=20130513122504.GA5246@dhcp22.suse.cz \
--to=mhocko@suse.cz \
--cc=akpm@linux-foundation.org \
--cc=cgroups@vger.kernel.org \
--cc=gthelen@google.com \
--cc=handai.szj@gmail.com \
--cc=handai.szj@taobao.com \
--cc=hughd@google.com \
--cc=kamezawa.hiroyu@jp.fujitsu.com \
--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 a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox