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

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Message-ID: <0e01d912-9473-35df-5bc7-f080ab9c1818@suse.cz>
Date:   Fri, 17 Mar 2017 19:29:54 +0100
From:   Vlastimil Babka <vbabka@...e.cz>
To:     Johannes Weiner <hannes@...xchg.org>
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 03/16/2017 07:34 PM, Johannes Weiner wrote:
> 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
> 
> ;)

Great!

>> 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

That's better than I expected. I wouldn't be surprised if the number of
unmovable pageblocks actually got *higher* due to the series because
previously many unmovable pages would be scattered around movable blocks.

> 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!

Thanks a lot! So that means it's worth the increased compaction stats
you reported earlier?