[PATCH xserver 01/20] Remove non-smart scheduler. Don't require setitimer.

[Adam Jackson]

On Wed, 2015-11-11 at 22:02 -0800, Keith Packard wrote:
> This allows the server to call GetTimeInMillis() after each request is
> processed to avoid needing setitimer. -dumbSched now turns off the
> setitimer.

I'm not sure there are real systems we'd be protecting by not requiring
setitimer.  But, at least on my Ivybridge, this only dings noop
performance by like 1% when using -dumbSched.  Probably this would be
worse on non-vdso setups, but anyone with both of those problems is
already in pretty bad shape.

Would also be nice to see doc/smartsched updated to reflect reality,
I'll take a crack at that.

> +#if HAVE_SETITIMER
>      if (SmartScheduleEnable() < 0) {
>          perror("sigaction for smart scheduler");
> -        SmartScheduleDisable = TRUE;
> +        SmartScheduleSignalEnable = FALSE;
>      }
> +#endif
>  }

I have a slight preference for doing like this in the header:

#ifndef HAVE_SETITIMER
#define SmartScheduleEnable() 0
#endif

> +#if HAVE_SETITIMER
>      if (SmartSchedulePause() < 0) {
>          close(pdes[0]);
>          close(pdes[1]);

... same.  A bit cosmetic I suppose.

- ajax