From: Dave Jones <davej@redhat.com>
To: linux-kernel@vger.kernel.org
Cc: 76306.1226@compuserve.com, mingo@elte.hu
Subject: Re: + spinlock_debug-dont-recompute-jiffies_per_loop.patch added to -mm tree
Date: Tue, 25 Jul 2006 16:42:28 -0400 [thread overview]
Message-ID: <20060725204228.GE13829@redhat.com> (raw)
In-Reply-To: <200607251910.k6PJASfo006168@shell0.pdx.osdl.net>
On Tue, Jul 25, 2006 at 12:10:28PM -0700, Andrew Morton wrote:
>
> The patch titled
>
> spinlock_debug: don't recompute (jiffies_per_loop applied-patches arch backup bin block config-x COPYING CREDITS CREDITS~git-gfs2 crypto CVS Documentation drivers fs include init ipc Kbuild kernel lib linus-series log mach MAINTAINERS MAINTAINERS~avr32-arch MAINTAINERS~edac-new-opteron-athlon64-memory-controller-driver MAINTAINERS~git-gfs2 MAINTAINERS~git-klibc MAINTAINERS.orig MAINTAINERS~origin MAINTAINERS~qla3xxx-NIC-driver MAINTAINERS~x86_64-mm-add-a-maintainers-entry-for-calgary Makefile Makefile~git-kbuild Makefile~git-klibc Makefile~mm Makefile.orig Makefile.rej mm net notes patches pc README REPORTING-BUGS scripts security series 'series sound Tags test.img txt usr HZ) in spinloop
>
> has been added to the -mm tree. Its filename is
Wow, that's umm, spectacular ;-)
> ------------------------------------------------------
> Subject: spinlock_debug: don't recompute (jiffies_per_loop applied-patches arch backup bin block config-x COPYING CREDITS CREDITS~git-gfs2 crypto CVS Documentation drivers fs include init ipc Kbuild kernel lib linus-series log mach MAINTAINERS MAINTAINERS~avr32-arch MAINTAINERS~edac-new-opteron-athlon64-memory-controller-driver MAINTAINERS~git-gfs2 MAINTAINERS~git-klibc MAINTAINERS.orig MAINTAINERS~origin MAINTAINERS~qla3xxx-NIC-driver MAINTAINERS~x86_64-mm-add-a-maintainers-entry-for-calgary Makefile Makefile~git-kbuild Makefile~git-klibc Makefile~mm Makefile.orig Makefile.rej mm net notes patches pc README REPORTING-BUGS scripts security series 'series sound Tags test.img txt usr HZ) in spinloop
> From: Chuck Ebbert <76306.1226@compuserve.com>
>
> In spinlock_debug.c, the spinloops call __delay() on every iteration.
> Because that is an external function, (jiffies_per_loop * HZ), the loop's
> iteration limit, gets recomputed every time. Caching it explicitly
> prevents that.
What is the purpose of those __delays being there at all ?
Seems odd to be waiting that long when the spinlock could become available
a lot sooner. (These also make spinlock debug really painful
on boxes with huge numbers of CPUs).
Dave
--
http://www.codemonkey.org.uk
next parent reply other threads:[~2006-07-25 20:44 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <200607251910.k6PJASfo006168@shell0.pdx.osdl.net>
2006-07-25 20:42 ` Dave Jones [this message]
2006-07-25 20:43 ` + spinlock_debug-dont-recompute-jiffies_per_loop.patch added to -mm tree Ingo Molnar
2006-07-27 5:53 Chuck Ebbert
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