linux-kernel - Re: [PATCH v2 0/5] introduce kcompactd and stop compacting in kswapd

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Message-ID: <56E1329F.3040600@suse.cz>
Date:	Thu, 10 Mar 2016 09:38:55 +0100
From:	Vlastimil Babka <vbabka@...e.cz>
To:	Michal Hocko <mhocko@...nel.org>
Cc:	linux-mm@...ck.org, Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org,
	Andrea Arcangeli <aarcange@...hat.com>,
	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
	Rik van Riel <riel@...hat.com>,
	Joonsoo Kim <iamjoonsoo.kim@....com>,
	Mel Gorman <mgorman@...hsingularity.net>,
	David Rientjes <rientjes@...gle.com>,
	Johannes Weiner <hannes@...xchg.org>
Subject: Re: [PATCH v2 0/5] introduce kcompactd and stop compacting in kswapd

On 03/09/2016 04:52 PM, Michal Hocko wrote:
> On Mon 08-02-16 14:38:06, Vlastimil Babka wrote:
>> The previous RFC is here [1]. It didn't have a cover letter, so the description
>> and results are in the individual patches.
>
> FWIW I think this is a step in the right direction. I would give my

Thanks!

> Acked-by to all patches but I wasn't able to find time for a deep review
> and my lack of knowledge of compaction details doesn't help much. I do
> agree that conflating kswapd with compaction didn't really work out well
> and fixing this would just make the code more complex and would more
> prone to new bugs.

Yeah, it seems that direct reclaim/compaction is complex enough already...

> In future we might want to invent something similar
> to watermarks and set an expected level of high order pages prepared for
> the allocation (e.g. have at least XMB of memory in order-9+). kcompact
> then could try as hard as possible to provide them. Does that sound at
> least doable?

Sure, that was/is part of the plan. But I was trimming the series for 
initial merge over the past year to arrive at a starting point where 
reaching consensus is easier.

> Thanks!
>