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Date: Thu, 2 Apr 2015 09:54:43 +0200
From: Peter Zijlstra <peterz@infradead.org>
To: Huang Ying <ying.huang@intel.com>
Cc: Viresh Kumar <viresh.kumar@linaro.org>,
        LKML <linux-kernel@vger.kernel.org>, LKP ML <lkp@01.org>
Subject: Re: [LKP] [timer] 17cdf560f27: +4.0% boot-meminfo.VmallocUsed
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On Thu, Apr 02, 2015 at 09:06:09AM +0800, Huang Ying wrote:
> FYI, we noticed the below changes on
> 
> git://git.kernel.org/pub/scm/linux/kernel/git/vireshk/linux.git timer/alloc_tvec_statically
> commit 17cdf560f2727f687ab159707d0aa591f8a2f82d ("timer: Allocate per-cpu tvec_base's statically")
> 
> 
> testbox/testcase/testparams: lkp-sbx04/boot/performance-1
> 
> c5e77f5216abdd1d  17cdf560f2727f687ab159707d  
> ----------------  --------------------------  
>          %stddev     %change         %stddev
>              \          |                \  
>     410996 ±  0%      +4.0%     427412 ±  0%  boot-meminfo.VmallocUsed
> 
> testbox/testcase/testparams: wsm/boot/performance-1
> 
> c5e77f5216abdd1d  17cdf560f2727f687ab159707d  
> ----------------  --------------------------  
>      85712 ±  0%      +2.4%      87772 ±  0%  boot-meminfo.VmallocUsed
> 
> testbox/testcase/testparams: lkp-snb01/boot/performance-1
> 
> c5e77f5216abdd1d  17cdf560f2727f687ab159707d  
> ----------------  --------------------------  
>     447001 ±  0%      -1.0%     442558 ±  0%  boot-slabinfo.num_objs
>     125616 ±  5%     -13.5%     108720 ±  4%  boot-meminfo.DirectMap4k
>     347196 ±  0%      +4.7%     363612 ±  0%  boot-meminfo.VmallocUsed
> 

well, duh.. it changes a dynamic allocation into a static per-cpu one.
What did you expect?