On Wed, 8 Feb 2012 19:02:47 +0100, Daniel Vetter <daniel at ffwll.ch> wrote: > The issue is that the first one introduces a pretty decent perf > regression, iirc Chris mentions something much large than 10x slowdown > on certain cairo traces on sna. So we can only merge the first one > together with the second one. As it turns out, the cairo-traces were successfully exploiting the ringbuffer overflow to avoid work. The reason why it eventually broke is that when I experimented with using the BLT and semaphores, I introduced a dependency on accurate seqno processing, which was obviously broken by the overwriting of commands in the ringbuffer. And so is consistent with the hangs reported by Eugeni and Ben, but we have yet to see many more examples in the wild. Otoh, I don't think this explains the all-generation use-after-free bug. Net result, the 0.9s firefox-paintball result was a fantasy and the perf gains provided by the second patch are only around 20% for the same trace. Ergo -next material only if it passes scrutiny. -Chris -- Chris Wilson, Intel Open Source Technology Centre
