Messages in this thread | | | Date | Tue, 3 Oct 2006 17:07:05 -0700 | From | Andrew Morton <> | Subject | Re: [PATCH] Fix WARN_ON / WARN_ON_ONCE regression |
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On Tue, 03 Oct 2006 16:04:04 -0700 Tim Chen <tim.c.chen@linux.intel.com> wrote:
> Hi Herbet, > > The patch "Let WARN_ON/WARN_ON_ONCE return the condition" > http://kernel.org/git/? > p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=684f978347deb42d180373ac4c427f82ef963171 > > introduced 40% more 2nd level cache miss to tbench workload > being run in a loop back mode on a Core 2 machine. I think the > introduction of the local variables to WARN_ON and WARN_ON_ONCE > > typeof(x) __ret_warn_on = (x); > typeof(condition) __ret_warn_once = (condition); > > results in the extra cache misses.
I don't see why it should.
Perhaps the `static int __warn_once' is getting put in the same cacheline as some frequently-modified thing. Perhaps try marking that as __read_mostly?
> In our test workload profile, we see > heavily used functions like do_softirq and local_bh_enable > takes a lot longer to execute. > > The modification below helps fix the problem. I made a slight > modification to sched.c to get around a gcc bug. > > Signed-off-by: Tim Chen <tim.c.chen@intel.com> > diff --git a/include/asm-generic/bug.h b/include/asm-generic/bug.h > index a525089..05ed388 100644 > --- a/include/asm-generic/bug.h > +++ b/include/asm-generic/bug.h > @@ -17,13 +17,12 @@ #endif > > #ifndef HAVE_ARCH_WARN_ON > #define WARN_ON(condition) > ({ \ > - typeof(condition) __ret_warn_on = > (condition); \ > - if (unlikely(__ret_warn_on)) > { \ > + if (unlikely(condition)) > { \ > printk("BUG: warning at %s:%d/%s()\n", > __FILE__, \
Your patch is extremely wordwrapped. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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