linux-kernel - Re: [PATCH v3 0/8] try to reduce fragmenting fallbacks

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Date:   Thu, 16 Mar 2017 14:34:22 -0400
From:   Johannes Weiner <hannes@...xchg.org>
To:     Vlastimil Babka <vbabka@...e.cz>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        Mel Gorman <mgorman@...hsingularity.net>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        David Rientjes <rientjes@...gle.com>, kernel-team@...com
Subject: Re: [PATCH v3 0/8] try to reduce fragmenting fallbacks

On Wed, Mar 08, 2017 at 08:17:39PM +0100, Vlastimil Babka wrote:
> On 8.3.2017 17:46, Johannes Weiner wrote:
> > Is there any other data you would like me to gather?
> 
> If you can enable the extfrag tracepoint, it would be nice to have graphs of how
> unmovable allocations falling back to movable pageblocks, etc.

Okay, here we go. I recorded 24 hours worth of the extfrag tracepoint,
filtered to fallbacks from unmovable requests to movable blocks. I've
uploaded the plot here:

http://cmpxchg.org/antifrag/fallbackrate.png

but this already speaks for itself:

11G     alloc-mtfallback.trace
3.3G    alloc-mtfallback-patched.trace

;)

> Possibly also /proc/pagetypeinfo for numbers of pageblock types.

After a week of uptime, the patched (b) kernel has more movable blocks
than vanilla 4.10-rc8 (a):

   Number of blocks type     Unmovable      Movable  Reclaimable   HighAtomic          CMA      Isolate

a: Node 1, zone   Normal         2017        29763          987            1            0            0
b: Node 1, zone   Normal         1264        30850          653            1            0            0

I sampled this somewhat sporadically over the week and it's been
reading reliably this way.

The patched kernel also consistently beats vanilla in terms of peak
job throughput.

Overall very cool!