From: Konstantin Khlebnikov <khlebnikov@openvz.org>
To: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Hugh Dickins <hughd@google.com>,
"linux-mm@kvack.org" <linux-mm@kvack.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 3/3] mm: adjust rss counters for migration entiries
Date: Wed, 11 Jan 2012 12:23:11 +0400 [thread overview]
Message-ID: <4F0D46EF.4060705@openvz.org> (raw)
In-Reply-To: <20120111144125.0c61f35f.kamezawa.hiroyu@jp.fujitsu.com>
KAMEZAWA Hiroyuki wrote:
> On Fri, 06 Jan 2012 21:38:56 +0400
> Konstantin Khlebnikov<khlebnikov@openvz.org> wrote:
>
>> Memory migration fill pte with migration entry and it didn't update rss counters.
>> Then it replace migration entry with new page (or old one if migration was failed).
>> But between this two passes this pte can be unmaped, or task can fork child and
>> it will get copy of this migration entry. Nobody account this into rss counters.
>>
>> This patch properly adjust rss counters for migration entries in zap_pte_range()
>> and copy_one_pte(). Thus we avoid extra atomic operations on migration fast-path.
>>
>> Signed-off-by: Konstantin Khlebnikov<khlebnikov@openvz.org>
>
> It's better to show wheter this is a bug-fix or not in changelog.
>
> IIUC, the bug-fix is the 1st harf of this patch + patch [2/3].
> Your new bug-check code is in patch[1/3] and 2nd half of this patch.
>
No, there only one new bug-check in 1st patch, this is non-fatal warning.
I didn't hide this check under CONFIG_VM_DEBUG because it rather small and
rss counters covers whole page-table management, this is very good invariant.
Currently I can trigger this warning only on this rare race -- extremely loaded
memory compaction catches this every several seconds.
1/3 bug-check
2/3 fix preparation
3/3 bugfix in two places:
do rss++ in copy_one_pte()
do rss-- in zap_pte_range()
> I think it's better to do bug-fix 1st and add bug-check later.
>
> So, could you reorder patches to bug-fix and new-bug-check ?
Patches didn't share any context, so they can be applied in any order.
>
> To the logic itself,
> Acked-by: KAMEZAWA Hiroyuki<kamezawa.hiroyu@jp.fujitsu.com>
> Please CC when you repost.
>
>
>
--
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/ .
Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
WARNING: multiple messages have this Message-ID (diff)
From: Konstantin Khlebnikov <khlebnikov@openvz.org>
To: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Hugh Dickins <hughd@google.com>,
"linux-mm@kvack.org" <linux-mm@kvack.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 3/3] mm: adjust rss counters for migration entiries
Date: Wed, 11 Jan 2012 12:23:11 +0400 [thread overview]
Message-ID: <4F0D46EF.4060705@openvz.org> (raw)
In-Reply-To: <20120111144125.0c61f35f.kamezawa.hiroyu@jp.fujitsu.com>
KAMEZAWA Hiroyuki wrote:
> On Fri, 06 Jan 2012 21:38:56 +0400
> Konstantin Khlebnikov<khlebnikov@openvz.org> wrote:
>
>> Memory migration fill pte with migration entry and it didn't update rss counters.
>> Then it replace migration entry with new page (or old one if migration was failed).
>> But between this two passes this pte can be unmaped, or task can fork child and
>> it will get copy of this migration entry. Nobody account this into rss counters.
>>
>> This patch properly adjust rss counters for migration entries in zap_pte_range()
>> and copy_one_pte(). Thus we avoid extra atomic operations on migration fast-path.
>>
>> Signed-off-by: Konstantin Khlebnikov<khlebnikov@openvz.org>
>
> It's better to show wheter this is a bug-fix or not in changelog.
>
> IIUC, the bug-fix is the 1st harf of this patch + patch [2/3].
> Your new bug-check code is in patch[1/3] and 2nd half of this patch.
>
No, there only one new bug-check in 1st patch, this is non-fatal warning.
I didn't hide this check under CONFIG_VM_DEBUG because it rather small and
rss counters covers whole page-table management, this is very good invariant.
Currently I can trigger this warning only on this rare race -- extremely loaded
memory compaction catches this every several seconds.
1/3 bug-check
2/3 fix preparation
3/3 bugfix in two places:
do rss++ in copy_one_pte()
do rss-- in zap_pte_range()
> I think it's better to do bug-fix 1st and add bug-check later.
>
> So, could you reorder patches to bug-fix and new-bug-check ?
Patches didn't share any context, so they can be applied in any order.
>
> To the logic itself,
> Acked-by: KAMEZAWA Hiroyuki<kamezawa.hiroyu@jp.fujitsu.com>
> Please CC when you repost.
>
>
>
next prev parent reply other threads:[~2012-01-11 8:23 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-01-06 17:38 [PATCH 1/3] mm: add rss counters consistency check Konstantin Khlebnikov
2012-01-06 17:38 ` Konstantin Khlebnikov
2012-01-06 17:38 ` [PATCH 2/3] mm: postpone migrated page mapping reset Konstantin Khlebnikov
2012-01-06 17:38 ` Konstantin Khlebnikov
2012-01-06 17:38 ` [PATCH 3/3] mm: adjust rss counters for migration entiries Konstantin Khlebnikov
2012-01-06 17:38 ` Konstantin Khlebnikov
2012-01-06 17:45 ` Konstantin Khlebnikov
2012-01-11 5:41 ` KAMEZAWA Hiroyuki
2012-01-11 5:41 ` KAMEZAWA Hiroyuki
2012-01-11 8:23 ` Konstantin Khlebnikov [this message]
2012-01-11 8:23 ` Konstantin Khlebnikov
2012-01-11 8:41 ` KAMEZAWA Hiroyuki
2012-01-11 8:41 ` KAMEZAWA Hiroyuki
2012-01-18 23:21 ` Andrew Morton
2012-01-18 23:21 ` Andrew Morton
2012-01-24 1:42 ` Hugh Dickins
2012-01-24 1:42 ` Hugh Dickins
2012-01-24 7:08 ` Konstantin Khlebnikov
2012-01-24 7:08 ` Konstantin Khlebnikov
2012-01-25 23:01 ` Hugh Dickins
2012-01-25 23:01 ` Hugh Dickins
2012-01-26 0:20 ` Andrew Morton
2012-01-26 0:20 ` Andrew Morton
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=4F0D46EF.4060705@openvz.org \
--to=khlebnikov@openvz.org \
--cc=akpm@linux-foundation.org \
--cc=hughd@google.com \
--cc=kamezawa.hiroyu@jp.fujitsu.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.