On Fri, May 29, 2015 at 06:14:46PM -0400, Yogi A. Patel wrote: > > > On 05/28/2015 08:54 PM, Michel Dänzer wrote: > > Can you narrow down when the problem was introduced in the kernel, > > ideally with git bisect? > >
> I did a few experiments and here is an update: > > + It seems that whatever is causing this is from drm/radeon and it came in > sometime between 3.8.13 and 3.10.32. The dmesg output from 3.10.32 is > attached, too > > + the latencies are worse on 3.14 (40us) than on 3.10 (20-30us) regardless of > the card. > > + latencies on 3.8 for both cards are below 10us. > Just in case you don't realise how stable kernel releases happen: First, Linus release .0. For most people, these kernels work ok most of the time. Then gradual fixes appear during the development of a later kernel, and get applied by the stable team. So, I suggest that an approach something like this might help: Begin by testing 3.10.0 and (ideally) 3.8.0. Is 3.10.0 worse than 3.8 ? If it is, the problem was introduced between 3.8 (good) and 3.10 (bad) and you can bisect linus's tree. If 3.10.0 was good, the problem appeared in the 3.10 _stable_ tree. For something like that, I have on occasion been tempted to take a broad-brush initial approach and try the released versions - in this case I might begin by trying e.g. 3.10.16, 3.10.8 or 3.10.24, etc to get a better feeling for when it went bad. But ultimately, bisecting the 3.10 stable tree will be the way to go. Also, it sounds as if 3.14 is a different, or extra, problem. Would it be practical for you to move to a newer version if that solved the problem ? If so, you could try 4.0.latest just in case it is already fixed. A couple of times, I've had to do bisection in -rc kernels, only to discover that a commit during the current week had already removed the problem I had. ĸen -- Nanny Ogg usually went to bed early. After all, she was an old lady. Sometimes she went to bed as early as 6 a.m. _______________________________________________ xorg-driver-ati mailing list [email protected] http://lists.x.org/mailman/listinfo/xorg-driver-ati
