linux-kernel - Re: [kernfs] ea7c5fc39a: stress-ng.stream.ops_per

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Date:   Sat, 6 Jun 2020 20:18:02 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     kernel test robot <rong.a.chen@...el.com>
Cc:     Ian Kent <raven@...maw.net>,
        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 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?

thanks,

greg k-h