Perf degradation from -rt14 onwards

[Dinakar Guniguntala <dino@in.ibm.com>]

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.

	-Dinakar

-
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/