linux-kernel - Re: [LKP] [lkp] [dcache_{readdir, dir_lseek}() users] 4e82901cd6: reaim.jobs_per

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Date:	Sun, 26 Jun 2016 19:06:04 +0100
From:	Al Viro <viro@...IV.linux.org.uk>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Thorsten Leemhuis <regressions@...mhuis.info>,
	"Huang, Ying" <ying.huang@...el.com>, LKP <lkp@...org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [LKP] [lkp] [dcache_{readdir, dir_lseek}() users] 4e82901cd6:
 reaim.jobs_per_min -49.1% regression

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@...mhuis.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.