[Libva] CPU usage regression

[Yuan, Shengquan]

On Wed, Jun 8, 2011 at 6:00 PM, gimli <gimli at dark-green.com> wrote:
> I was hitting a performance regression in libva on ILK and SNA.
> Did a bisect of the git changes and found the root cause.
> In commit 0d97d088493f2b62dd1b55df26f26775eb20d85c
>
> diff --git a/va/x11/va_dri2.c b/va/x11/va_dri2.c
> index 4915651..8e9f304 100644
> --- a/va/x11/va_dri2.c
> +++ b/va/x11/va_dri2.c
> @@ -340,9 +340,9 @@ void VA_DRI2SwapBuffers(Display *dpy, XID drawable,
> CARD64 target_msc,
> req->drawable = drawable;
> load_swap_req(req, target_msc, divisor, remainder);
>
> -    _XReply(dpy, (xReply *)&rep, 0, xFalse);
> +    _XSend(dpy, NULL, 0);

The original intent of changing from _XReply to _XSend is that with
_XSend  we can gain some FPS.

Are you saying it will increase CPU usage? I understand _XReplay waits
until Xserver returns the result, and
_XSend just sends the request, is that true?

Thanks
-Austin

>
> -    *count = vals_to_card64(rep.swap_lo, rep.swap_hi);
> +    *count = 0;
>
> UnlockDisplay(dpy);
> SyncHandle();
>
> This is causing in a running application a permanent growing of the CPU
> usage.
> The attached patch revert this to the old behavior where the CPU usage
> remains constant.
>
> Signed-off-by: Edgar Hucek <gimli at dark-green.com>