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Date: Thu, 11 Jun 2020 10:06:57 +0800 From: kernel test robot <rong.a.chen@...el.com> To: Ian Kent <raven@...maw.net> Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>, Andrew Morton <akpm@...ux-foundation.org>, Al Viro <viro@...iv.linux.org.uk>, Tejun Heo <tj@...nel.org>, Rick Lindsley <ricklind@...ux.vnet.ibm.com>, Stephen Rothwell <sfr@...b.auug.org.au>, David Howells <dhowells@...hat.com>, Miklos Szeredi <miklos@...redi.hu>, linux-fsdevel <linux-fsdevel@...r.kernel.org>, Kernel Mailing List <linux-kernel@...r.kernel.org>, lkp@...ts.01.org Subject: Re: [kernfs] ea7c5fc39a: stress-ng.stream.ops_per_sec 11827.2% improvement On Sun, Jun 07, 2020 at 09:13:08AM +0800, Ian Kent wrote: > On Sat, 2020-06-06 at 20:18 +0200, Greg Kroah-Hartman wrote: > > On Sat, Jun 06, 2020 at 11:52:16PM +0800, kernel test robot wrote: > > > Greeting, > > > > > > FYI, we noticed a 11827.2% improvement of stress- > > > ng.stream.ops_per_sec due to commit: > > > > > > > > > commit: ea7c5fc39ab005b501e0c7666c29db36321e4f74 ("[PATCH 1/4] > > > kernfs: switch kernfs to use an rwsem") > > > url: > > > https://github.com/0day-ci/linux/commits/Ian-Kent/kernfs-proposed-locking-and-concurrency-improvement/20200525-134849 > > > > > > > Seriously? That's a huge performance increase, and one that feels > > really odd. Why would a stress-ng test be touching sysfs? > > That is unusually high even if there's a lot of sysfs or kernfs > activity and that patch shouldn't improve VFS path walk contention > very much even if it is present. > > Maybe I've missed something, and the information provided doesn't > seem to be quite enough to even make a start on it. > > That's going to need some analysis which, for my part, will need to > wait probably until around rc1 time frame to allow me to get through > the push down stack (reactive, postponed due to other priorities) of > jobs I have in order to get back to the fifo queue (longer term tasks, > of which this is one) list of jobs I need to do as well, ;) > > Please, kernel test robot, more information about this test and what > it's doing. > Hi Ian, We increased the timeout of stress-ng from 1s to 32s, and there's only 3% improvement of stress-ng.stream.ops_per_sec: fefcfc968723caf9 ea7c5fc39ab005b501e0c7666c testcase/testparams/testbox ---------------- -------------------------- --------------------------- %stddev change %stddev \ | \ 10686 3% 11037 stress-ng/cpu-cache-performance-1HDD-100%-32s-ucode=0x500002c/lkp-csl-2sp5 10686 3% 11037 GEO-MEAN stress-ng.stream.ops_per_sec It seems the result of stress-ng is inaccurate if test time too short, we'll increase the test time to avoid unreasonable results, sorry for the inconvenience. Best Regards, Rong Chen
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