[Dri-devel] XvShmPutImage on r128 eating too much CPU, round 4

[Peter S. <shu...@pa...>]

Hi!

Preface for those who don't remember: playing videos on r128 with
XvShmPutImage used to take a lot of CPU time, about 25% for DVD, inside
SYSTEM. The cause was found to be slow videoram and was solved by using DRI's
DMA functions. Suddenly, several months later, roughly the same amount of CPU
again started to be consumed, this time in userspace though, even if DRI is
enabled. If DRI is disabled, it is even worse: CPU time is eaten both in
SYSTEM and USER, consuming a total of about 50% CPU while basically doing
nothing.

I have yet another idea what could be causing this.

As Volodya said, calling XvShmPutImage doesn't actually put the stuff on the
screen, it just queues it and returns. A client application (in my case SDL
and Mplayer's vo_xv) then calls XSync (or XFlush) immediately afterwards. I
assume XSync does a busy loop, which "eats CPU time". This theory seems to
explain the behaviour better than others (e.g. why the load takes place in
USER and why turning off DRI doesn't help).

Still unknown is why it appeared in the 4.1.99 times. Does anyone remember
changing either XSync or XvShmPutImage behaviour?

Comments, ideas?

Bye,

Peter Surda (Shurdeek) <shu...@pa...>, ICQ 10236103, +436505122023

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