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From: Al Viro <viro@ZenIV.linux.org.uk>
To: lkp@lists.01.org
Subject: Re: [dcache_{readdir, dir_lseek}() users] 4e82901cd6: reaim.jobs_per_min -49.1% regression
Date: Sun, 26 Jun 2016 19:06:04 +0100
Message-ID: <20160626180604.GW14480@ZenIV.linux.org.uk>
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On Sun, Jun 26, 2016 at 10:13:32AM -0700, Linus Torvalds wrote:
> On Sun, Jun 26, 2016 at 2:50 AM, Thorsten Leemhuis
> <regressions@leemhuis.info> wrote:
> >
> > Al, what's the status here? This made it on my 4.7 regressions report
> > due to the "regression" keyword in the subject.
> =

> I don't think the tmpfs locking is going to get changed for 4.7. This
> issue will likely only show up for some very specific microbenchmarks,
> and the lockless next_positive one is likely too invasive for this
> stage. So the problem is fixable, and not serious enough to worry
> about for 4.7.

FWIW, #work.dcache_readdir in vfs.git seems to recover the performance.
Not sure if it's worth pushing right now, but if it ends up the next
cycle stuff, I think it'll be worth Cc:stable.

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Date: Sun, 26 Jun 2016 19:06:04 +0100
From: Al Viro <viro@ZenIV.linux.org.uk>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Thorsten Leemhuis <regressions@leemhuis.info>,
        "Huang, Ying" <ying.huang@intel.com>, LKP <lkp@01.org>,
        LKML <linux-kernel@vger.kernel.org>
Subject: Re: [LKP] [lkp] [dcache_{readdir, dir_lseek}() users] 4e82901cd6:
 reaim.jobs_per_min -49.1% regression
Message-ID: <20160626180604.GW14480@ZenIV.linux.org.uk>
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 <20160602162956.GH14480@ZenIV.linux.org.uk>
 <d7cc4340-7a21-f862-bce1-c3dd395bd926@leemhuis.info>
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On Sun, Jun 26, 2016 at 10:13:32AM -0700, Linus Torvalds wrote:
> On Sun, Jun 26, 2016 at 2:50 AM, Thorsten Leemhuis
> <regressions@leemhuis.info> wrote:
> >
> > Al, what's the status here? This made it on my 4.7 regressions report
> > due to the "regression" keyword in the subject.
> 
> I don't think the tmpfs locking is going to get changed for 4.7. This
> issue will likely only show up for some very specific microbenchmarks,
> and the lockless next_positive one is likely too invasive for this
> stage. So the problem is fixable, and not serious enough to worry
> about for 4.7.

FWIW, #work.dcache_readdir in vfs.git seems to recover the performance.
Not sure if it's worth pushing right now, but if it ends up the next
cycle stuff, I think it'll be worth Cc:stable.