linux-kernel - Re: question on NUMA page migration

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Date:	Sat, 20 Oct 2012 12:02:32 -0400
From:	Rik van Riel <riel@...hat.com>
To:	Ingo Molnar <mingo@...nel.org>
CC:	Peter Zijlstra <peterz@...radead.org>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Linux Memory Management List <linux-mm@...ck.org>,
	Mel Gorman <mel@....ul.ie>,
	Linux kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: question on NUMA page migration

On 10/19/2012 09:23 PM, Ingo Molnar wrote:
>
> * Rik van Riel <riel@...hat.com> wrote:
>
>> On 10/19/2012 01:53 PM, Peter Zijlstra wrote:
>>> On Fri, 2012-10-19 at 13:13 -0400, Rik van Riel wrote:
>>
>>>> Another alternative might be to do the put_page inside
>>>> do_prot_none_numa().  That would be analogous to do_wp_page
>>>> disposing of the old page for the caller.
>>>
>>> It'd have to be inside migrate_misplaced_page(), can't do before
>>> isolate_lru_page() or the page might disappear. Doing it after is
>>> (obviously) too late.
>>
>> Keeping an extra refcount on the page might _still_
>> result in it disappearing from the process by some
>> other means, in-between you grabbing the refcount
>> and invoking migration of the page.
>>
>>>> I am not real happy about NUMA migration introducing its own
>>>> migration mode...
>>>
>>> You didn't seem to mind too much earlier, but I can remove it if you
>>> want.
>>
>> Could have been reviewing fatigue :)
>
> :-)
>
>> And yes, it would have been nice to not have a special
>> migration mode for sched/numa.
>>
>> Speaking of, when do you guys plan to submit a (cleaned up)
>> version of the sched/numa patch series for review on lkml?
>
> Which commit(s) worry you specifically?

One of them would be the commit that introduces MIGRATE_FAULT.
Adding it in one patch, and removing it into a next just makes
things harder on the reviewers.

03a040f6c17ab81659579ba6abe267c0562097e4


If the changesets with NUMA syscalls are still in your tree's
history, they should not be submitted as part of the patch
series, either.
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