Messages in this thread |  | | | Date | Tue, 3 Oct 2006 20:32:44 -0700 | | From | Andrew Morton <> | | Subject | Re: [PATCH] Fix WARN_ON / WARN_ON_ONCE regression |
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On Tue, 3 Oct 2006 23:24:27 -0400 Andrew James Wade <andrew.j.wade@gmail.com> wrote:
> On Tuesday 03 October 2006 21:14, Andrew Morton wrote: > > There are changes here: in the old code we'll avoid reading the static > > variable. In the new code we'll read the static variable, but we'll avoid > > evaluating the condition. > > Tim Chen's patch goes back to the old behaviour. I suspect the cache > misses on __warn_once is what he is measuring. If so, the (untested) > patch below should reduce the cache misses back to those of the old > code. > > signed-off-by: Andrew Wade <andrew.j.wade@gmail.com> > diff -rupN a/include/asm-generic/bug.h b/include/asm-generic/bug.h > --- a/include/asm-generic/bug.h 2006-10-03 13:58:40.000000000 -0400 > +++ b/include/asm-generic/bug.h 2006-10-03 23:17:37.000000000 -0400 > @@ -45,9 +45,10 @@ > static int __warn_once = 1; \ > typeof(condition) __ret_warn_once = (condition);\ > \ > - if (likely(__warn_once)) \ > - if (WARN_ON(__ret_warn_once)) \ > + if (unlikely(__ret_warn_once) && __warn_once) { \ > __warn_once = 0; \ > + WARN_ON(1); \ > + }; \ > unlikely(__ret_warn_once); \ > })
It might help, but we still don't know what's going on (I think).
I mean, if cache misses against __warn_once were sufficiently high for it to affect performance, then __warn_once would be, err, in cache? - 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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