Re: Perf degradation from -rt14 onwards

[David Singleton]

Dinakar Guniguntala wrote:

> I was wondering why the following change was made from -rt14
> onwards.
>
>
> @@ -1634,7 +1531,7 @@ asmlinkage long sys_futex(u32 __user *ua
>                          int val3)
> {
>        struct timespec t;
> -       unsigned long timeout = MAX_SCHEDULE_TIMEOUT;
> +       unsigned long timeout = 0;
>
> This was introduced in patch-2.6.14-rt13-rf3 by David.
>
> This seems to return spurious -ETIMEDOUT errors even in the
> non-robust code and results in userspace (glibc) retrying
> several mutex operations before it succeeds. I was chasing
> down a degradation of performance of some testcases and was
> able to fix those by reverting this change back.
>  

Yes.  The default timeout should be set to MAX_SCHEDULE_TIMEOUT, not zero.

David

> 	-Dinakar
>
>  

-
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