vulkan/wsi: x11 acquire is slow
I've been debugging glmark on zink recently, and the perf gap between zink and radeonsi was baffling me: 10,000 fps on zink vs 25,000 fps on radeonsi. perf was pretty useless to a point, so I ended up doing manual instrumentation, which led me to one inevitable conclusion:
Mesa's x11 wsi is slow.
If I look at the timings for ANI over a few seconds, I get about 25,000ns. This initially seems pretty okay until the reality that 25,000fps from radeonsi means a maximum of 40,000ns per frame, and ANI is using over 60% of that.
By contrast, radeonsi's ANI in gallium's dri frontend averages about 5500ns, which is almost 5x faster.
I'm still not entirely sure what's going on here, but this should definitely be examined by more X11 experts.