linux-kernel - Re: Hack bench regression with CONFIG_SLUB_CPU

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Message-ID: <51F1263A.6070704@linux.vnet.ibm.com>
Date:	Thu, 25 Jul 2013 18:50:58 +0530
From:	Raghavendra K T <raghavendra.kt@...ux.vnet.ibm.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
CC:	netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	"David S. Miller" <davem@...emloft.net>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Eric Dumazet <edumazet@...gle.com>,
	Al Viro <viro@...iv.linux.org.uk>,
	Gao feng <gaofeng@...fujitsu.com>
Subject: Re: Hack bench regression with CONFIG_SLUB_CPU_PARTIAL disabled (info
 only)

On 07/25/2013 04:35 PM, Eric Dumazet wrote:
> On Thu, 2013-07-25 at 13:30 +0530, Raghavendra K T wrote:
>> Hi,
>>
>> While testing hackbench with 3.11-rc1 I observed hackbench testcase
>> took too long to complete (32 vcpu kvm guest on 32 core HT off machine).
>>
>> hackbench 1x degraded by 3 time (40sec vs 112sec)
>> hackbench 2x degraded by around 20time (90sec vs 1800 sec)
>>
>> When I bisected, I found that I had CONFIG_SLUB_CPU_PARTIAL
>> accidentally disabled.
>> I understand that  CONFIG_SLUB_CPU_PARTIAL=y by default and the config
>> option is to provide determinism for RT kernels and thus it is not a
>> problem.
>> But thought of sharing this here so that if somebody runs into same
>> issue accidently, it would save their time.
>
> Incidentally, what difference do you currently get with SLUB and SLAB ?
>

tested now,
hackbench 1x is  almost 2 times slower (40 vs 93)
hackbench 2x is almost 6times slower   (90sec vs 528)

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