linux-kernel - Re: [PATCH 1/3 v2] slub: prefetch next freelist pointer in __slab

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Message-ID: <CAAmzW4N88UW0p41W5ObRZzDHHe08jW4X+VkeDrTu3pNNzFNUFA@mail.gmail.com>
Date:	Thu, 5 Jul 2012 01:04:16 +0900
From:	JoonSoo Kim <js1304@...il.com>
To:	Pekka Enberg <penberg@...nel.org>
Cc:	Christoph Lameter <cl@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	Eric Dumazet <eric.dumazet@...il.com>,
	David Rientjes <rientjes@...gle.com>
Subject: Re: [PATCH 1/3 v2] slub: prefetch next freelist pointer in __slab_alloc()

2012/7/5 Pekka Enberg <penberg@...nel.org>:
> On Wed, Jul 4, 2012 at 6:45 PM, JoonSoo Kim <js1304@...il.com> wrote:
>>> Prefetching can also have negative effect on overall performance:
>>>
>>> http://lwn.net/Articles/444336/
>>
>> Thanks for good article which is very helpful to me.
>>
>>> That doesn't seem like that obvious win to me... Eric, Christoph?
>>
>> Could you tell me how I test this patch more deeply, plz?
>> I am a kernel newbie and in the process of learning.
>> I doesn't know what I can do more for this.
>> I googling previous patch related to slub, some people use netperf.
>>
>> Just do below is sufficient?
>> How is this test related to slub?
>>
>> for in in `seq 1 32`
>> do
>>  netperf -H 192.168.0.8 -v 0 -l -100000 -t TCP_RR > /dev/null &
>> done
>> wait
>
> The networking subsystem is sensitive to slab allocator performance
> which makes netperf an interesting benchmark, that's all.
>
> As for slab benchmarking, you might want to look at what Mel Gorman
> has done in the past:
>
> https://lkml.org/lkml/2009/2/16/252
>
> For something like prefetch optimization, you'd really want to see a
> noticeable win in some benchmark. The kind of improvement you're
> seeing with your patch is likely to be lost in the noise - or even
> worse, cause negative performance for real world workloads.

Okay.
Thanks for comments.
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