linux-kernel - Re: [LKP] [x86_64,entry] f04e05b81e4: -62.7% time.user

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Message-ID: <20141107064027.GA24745@yliu-dev.sh.intel.com>
Date:	Fri, 7 Nov 2014 14:40:27 +0800
From:	Yuanhan Liu <yuanhan.liu@...ux.intel.com>
To:	Andy Lutomirski <luto@...capital.net>
Cc:	LKP <lkp@...org>, LKML <linux-kernel@...r.kernel.org>
Subject: Re: [LKP] [x86_64,entry] f04e05b81e4: -62.7% time.user_time

On Thu, Nov 06, 2014 at 10:26:23PM -0800, Andy Lutomirski wrote:
> On Thu, Nov 6, 2014 at 10:00 PM, LKP <lkp@...org> wrote:
> > FYI, we noticed the below changes on
> >
> > git://git.kernel.org/pub/scm/linux/kernel/git/luto/linux.git x86/entry
> > commit f04e05b81e4d9ae88bee379f12176f551a24394a ("x86_64,entry: Use sysret to return to userspace when possible")
> >
> >
> > f2ee9bebb99dd4a4  f04e05b81e4d9ae88bee379f12  testbox/testcase/testparams
> > ----------------  --------------------------
> >          %stddev     %change         %stddev
> >              \          |                \
> >      24.09 ±  4%     -62.7%       8.99 ±  3%  lkp-wsx02/aim9/performance-300s-creat-clo
> >      24.09           -62.7%       8.99        GEO-MEAN time.user_time
> >
> 
> I don't really know how to interpret this.  Is this a good thing or a bad thing?

TBH, I don't, either. Here we just list the changes we captured, which
is then for your information to decide it's good or bad.

> 
> I actually expect this change to be a dramatic speedup for some
> workloads. 

Would you like to share your workload? If so, I can add them to our
testing system, and give feedback to you when datat is available.

> Any chance you can send me the .config, kernel command
> line, and whether you have any tracing features enabled?

.config and dmesg are attached.

	--yliu

View attachment "dmesg" of type "text/plain" (311294 bytes)

View attachment "config-3.18.0-rc3-wl-ath-g7c130ce" of type "text/plain" (126749 bytes)