[Nouveau] [PATCH] drm/nouveau: fix __nouveau_fence_wait performance regression

[Maarten Maathuis]

On Fri, Mar 4, 2011 at 4:49 PM, Marcin Slusarz <marcin.slusarz at gmail.com> wrote:
> On Sun, Feb 13, 2011 at 09:38:04PM +0100, Marcin Slusarz wrote:
>> Combination of locking and interchannel synchronization changes
>> uncovered poor behaviour of nouveau_fence_wait, which on HZ=100
>> configuration could waste up to 10 ms per call.
>> Depending on application, it lead to 10-30% FPS regression.
>> To fix it, shorten thread sleep time to 0.1 ms and ensure
>> spinning happens for at least one *full* tick.
>>
>> Signed-off-by: Marcin Slusarz <marcin.slusarz at gmail.com>
>> ---
>>  drivers/gpu/drm/nouveau/nouveau_fence.c |   10 ++++++++--
>>  1 files changed, 8 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/nouveau/nouveau_fence.c b/drivers/gpu/drm/nouveau/nouveau_fence.c
>> index 221b846..75ba5e2 100644
>> --- a/drivers/gpu/drm/nouveau/nouveau_fence.c
>> +++ b/drivers/gpu/drm/nouveau/nouveau_fence.c
>> @@ -27,6 +27,9 @@
>>  #include "drmP.h"
>>  #include "drm.h"
>>
>> +#include <linux/ktime.h>
>> +#include <linux/hrtimer.h>
>> +
>>  #include "nouveau_drv.h"
>>  #include "nouveau_ramht.h"
>>  #include "nouveau_dma.h"
>> @@ -230,9 +233,12 @@ int
>>  __nouveau_fence_wait(void *sync_obj, void *sync_arg, bool lazy, bool intr)
>>  {
>>       unsigned long timeout = jiffies + (3 * DRM_HZ);
>> -     unsigned long sleep_time = jiffies + 1;
>> +     unsigned long sleep_time = jiffies + 2;
>> +     ktime_t t;
>>       int ret = 0;
>>
>> +     t = ktime_set(0, NSEC_PER_MSEC / 10);
>> +
>>       while (1) {
>>               if (__nouveau_fence_signalled(sync_obj, sync_arg))
>>                       break;
>> @@ -245,7 +251,7 @@ __nouveau_fence_wait(void *sync_obj, void *sync_arg, bool lazy, bool intr)
>>               __set_current_state(intr ? TASK_INTERRUPTIBLE
>>                       : TASK_UNINTERRUPTIBLE);
>>               if (lazy && time_after_eq(jiffies, sleep_time))
>> -                     schedule_timeout(1);
>> +                     schedule_hrtimeout(&t, HRTIMER_MODE_REL);
>>
>>               if (intr && signal_pending(current)) {
>>                       ret = -ERESTARTSYS;
>> --
>> 1.7.4.rc3
>>
>
> ping again
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>

This looks ok to me, but I would like to get Ben Skeggs ok on this one
as well. So i've CC'ed him, hopefully he'll notice :-)

-- 
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river get wider between your thoughts and the things we do and say.