linux-kernel - Re: ipc,sem: sysv semaphore scalability

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Date:	Sat, 30 Mar 2013 10:02:29 +0700
From:	Emmanuel Benisty <benisty.e@...il.com>
To:	Davidlohr Bueso <davidlohr.bueso@...com>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Dave Jones <davej@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Rik van Riel <riel@...riel.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	hhuang@...hat.com, "Low, Jason" <jason.low2@...com>,
	Michel Lespinasse <walken@...gle.com>,
	Larry Woodman <lwoodman@...hat.com>,
	"Vinod, Chegu" <chegu_vinod@...com>,
	Peter Hurley <peter@...leysoftware.com>
Subject: Re: ipc,sem: sysv semaphore scalability

Hi Davidlohr,

On Sat, Mar 30, 2013 at 9:08 AM, Davidlohr Bueso <davidlohr.bueso@...com> wrote:
> Not sure which one liner you refer to, but, if you haven't already done
> so, please try with these fixes (queued in linux-next):
>
> http://git.kernel.org/cgit/linux/kernel/git/next/linux-next.git/commit/?id=a9cead0347283f3e72a39e7b76a3cc479b048e51
> http://git.kernel.org/cgit/linux/kernel/git/next/linux-next.git/commit/?id=4db64b89525ac357cba754c3120065adddd9ec31
>
> I've been trying to reproduce your twilight zone problem on five
> different machines now without any luck. Is there anything you're doing
> to trigger the issue? Does the machine boot ok and then do weird things,
> say after X starts, open some program, etc?

I was missing a9cead0, thanks. What I usually do is starting a
standard session, which looks like this:

init-+-5*[agetty]
     |-bash---startx---xinit-+-X---2*[{X}]
     |                       `-dwm---sh---sleep
     |-bash---chromium-+-chromium
     |                 |-chromium-+-chromium
     |                 |          `-2*[{chromium}]
     |
|-chromium-sandbo---chromium---chromium---4*[chromium---4*[{chromium}]]
     |                 `-65*[{chromium}]
     |-crond
     |-dbus-daemon
     |-klogd
     |-syslogd
     |-tmux-+-alsamixer
     |      |-bash---bash
     |      |-bash
     |      |-htop
     |      `-newsbeuter---{newsbeuter}
     |-udevd
     |-urxvtd-+-bash---pstree
     |        `-bash---tmux
     `-wpa_supplicant

Then I start building a random package and the problems start. They
may also happen without compiling but this seems to trigger the bug
quite quickly. Anyway, some progress here, I hope: dmesg seems to be
willing to reveal some secrets (using some pastebin service since this
is pretty big):

https://gist.github.com/anonymous/5275120

Thanks.
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