On Mon, May 18, 2015 at 3:04 PM, Christian König christian.koenig@amd.com wrote:
On 18.05.2015 20:50, Denys Vlasenko wrote:
On 05/18/2015 08:06 PM, Christian König wrote:
I'm actually surprised how often people come along with that. The last time we tried this it caused a noticeable performance drop.
Basic problem is that this line:
- if ((reg < rdev->rmmio_size || reg < RADEON_MIN_MMIO_SIZE) &&
!always_indirect)
optimizes away in most of the cases which reduces the call to a readl which is way faster than the spinlock path.
So this is a NAK,
Fair enough.
I'm preparing a v2 where the fast branch of r100_mm_{r,w}reg() will stay inlined.
Sounds good to be, but IIRC that was suggested the last time this came up as well. You might just want to google a bit why it wasn't done like this before submitting the patch for review.
BTW: Please CC the dri-devel list as well, cause not everybody is reading on linux-kernel.
http://lists.freedesktop.org/archives/dri-devel/2014-April/057349.html ... http://lists.freedesktop.org/archives/dri-devel/2014-April/057520.html
Actually Lauri was *inlining* the function, not out-of-lining. I made the suggestion (and you agreed at the time) that the slow-path should be kept out of line, but apparently there was still high CPU overhead as a result?
Cheers,
-ilia