Re: Performance drop on XDrawRectangles()

Thomas Richter
2014-01-08T17:49:45Z

On 01/08/2014 06:10 PM, Chris Wilson wrote:
> On Wed, Jan 08, 2014 at 04:57:52PM +0100, Thomas Richter wrote:
>> Hi folks,
>>
>> during the changes from 3.12rc7 to 3.13rc4, the performance of
>> XDrawRectangles() dropped considerably. Interestingly, it is not the
>> raw rectangles drawing operations that are slow, but it seems that
>> the "per-call" overhead has increased by one magnitude. In specific,
>> if you use the unmodified "x11pref" program:
>>
>
> Just to be clear: new = 3.13-rc4, old = 3.12-rc7 ?

Yes, exactly.

> I've taken a quick look at this on an ivb i7-3270qm, and see a 296kops/s
> to 248kops/s decrease. Not massive, and considering the difference in
> our hardware probably a distinct issue.

Well, note that a 1Ghz P-III / i830M is not an i7-3270qm. (-;

Did you made the changes in x11perf as I did? The bottleneck is not in
the actual rectangle rendering, it is somewhere in the call-path from
the application down to the hardware, i.e. the per-call overhead
increased by a factor of eight.

Kernel configuration is identical, as much as I could arrange it. X11
and higher level libraries are all identical, I only changed the kernel.

Greetings,
Thomas