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

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Message-ID: <CA+55aFwA6CpODkJwHFd59EbNxOrP-FHM+xG8Xcgeni2DBotGPA@mail.gmail.com>
Date:	Fri, 29 Mar 2013 11:43:25 -0700
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Dave Jones <davej@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Rik van Riel <riel@...riel.com>,
	Davidlohr Bueso <davidlohr.bueso@...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>,
	Stanislav Kinsbursky <skinsbursky@...allels.com>
Subject: Re: ipc,sem: sysv semaphore scalability

On Fri, Mar 29, 2013 at 9:17 AM, Dave Jones <davej@...hat.com> wrote:
>
> Now that I have that reverted, I'm not seeing msgrcv traces any more, but
> I've started seeing this..
>
> general protection fault: 0000 [#1] PREEMPT SMP DEBUG_PAGEALLOC

Do you have CONFIG_CHECKPOINT_RESTORE enabled? Does it go away if you
disable it?

I think I foud at least one bug in the MSG_COPY stuff: it leaks the
"copy" allocation if

    mode == SEARCH_LESSEQUAL

but maybe I'm misreading it. And that shouldn't cause the problem you
see, but it's indicative of how badly tested and thought through the
MSG_COPY code is.

Totally UNTESTED leak fix appended. Stanislav?

                     Linus

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