From: Bob Liu <lliubbo@gmail.com>
To: Wu Fengguang <fengguang.wu@intel.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
"akpm@linux-foundation.org" <akpm@linux-foundation.org>,
"linux-mm@kvack.org" <linux-mm@kvack.org>,
"mel@csn.ul.ie" <mel@csn.ul.ie>,
"kosaki.motohiro@jp.fujitsu.com" <kosaki.motohiro@jp.fujitsu.com>
Subject: Re: [PATCH] do_migrate_range: avoid failure as much as possible
Date: Mon, 25 Oct 2010 12:00:01 +0800 [thread overview]
Message-ID: <AANLkTinBTRBZFbc3+rqdKy7Ls28MOWvO46gjZ7pYcRHg@mail.gmail.com> (raw)
In-Reply-To: <20101025034833.GB15933@localhost>
On Mon, Oct 25, 2010 at 11:48 AM, Wu Fengguang <fengguang.wu@intel.com> wrote:
> On Mon, Oct 25, 2010 at 11:09:01AM +0800, KAMEZAWA Hiroyuki wrote:
>> On Mon, 25 Oct 2010 12:05:50 +0900
>> KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> wrote:
>>
>> > This changes behavior.
>> >
>> > This "ret" can be > 0 because migrate_page()'s return code is
>> > "Return: Number of pages not migrated or error code."
>> >
>> > Then,
>> > ret < 0 ===> maybe ebusy
>> > ret > 0 ===> some pages are not migrated. maybe PG_writeback or some
>> > ret == 0 ===> ok, all condition green. try next chunk soon.
>> >
>> > Then, I added "yield()" and --retrym_max for !ret cases.
>> ^^^^^^^^
>> wrong.
>>
>> The code here does
>>
>> ret == 0 ==> ok, all condition green, try next chunk.
>
> It seems reasonable to remove the drain operations for "ret == 0"
> case. That would help large NUMA boxes noticeably I guess.
>
>> ret > 0 ==> all pages are isolated but some pages cannot be migrated. maybe under I/O
>> do yield.
>
> Don't know how to deal with the possible "migration fail" pages --
> sorry I have no idea about that situation at all.
>
> Perhaps, OOM while offlining pages?
>
>> ret < 0 ==> some pages may not be able to be isolated. reduce retrycount and yield()
>
> Makes good sense.
>
> Thanks,
> Fengguang
>
Hi, Wu
What about acking these two patches first which doesn't change logic too much.
[PATCH 2/3] do_migrate_range: exit loop if not_managed is true.
[PATCH 3/3] do_migrate_range: reduce list_empty() check.
For the current, I think more work&discussion is needed and make a
clean one is better.
Thanks.
--
Regards,
--Bob
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next prev parent reply other threads:[~2010-10-25 4:00 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-10-25 2:47 Bob Liu
2010-10-25 2:40 ` KAMEZAWA Hiroyuki
2010-10-25 2:57 ` Wu Fengguang
2010-10-25 3:05 ` KAMEZAWA Hiroyuki
2010-10-25 3:09 ` KAMEZAWA Hiroyuki
2010-10-25 3:48 ` Wu Fengguang
2010-10-25 3:48 ` KAMEZAWA Hiroyuki
2010-10-25 4:06 ` Wu Fengguang
2010-10-25 4:34 ` KAMEZAWA Hiroyuki
2010-10-25 4:55 ` Wu Fengguang
2010-10-25 4:00 ` Bob Liu [this message]
2010-10-25 3:28 ` Wu Fengguang
2010-10-25 3:50 ` KAMEZAWA Hiroyuki
2010-10-25 3:06 ` Wu Fengguang
2010-10-25 3:16 ` Wu Fengguang
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