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 <[email protected]>
>
> 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
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