| Message ID | 20230324220013.191795-1-robdclark@gmail.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | drm/msm: Avoid rounding down to zero jiffies | expand |
On 25/03/2023 00:00, Rob Clark wrote: > From: Rob Clark <robdclark@chromium.org> > > If userspace asked for a timeout greater than zero, but less than a > jiffy, they clearly weren't planning on spinning. So it is better > to round up to one. > > This fixes an issue with supertuxkart that was (for some reason) > spinning on a gl sync with 1ms timeout. CPU time for a demo lap > drops from: > > 15.83user 20.98system 0:47.46elapsed 77%CPU > > to: > > 8.84user 2.30system 0:46.67elapsed 23%CPU Interesting. We potentially increased the timeout, but the overall (elapsed) time has decreased. Nevertheless: Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org> > > Signed-off-by: Rob Clark <robdclark@chromium.org> > --- > drivers/gpu/drm/msm/msm_drv.h | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/gpu/drm/msm/msm_drv.h b/drivers/gpu/drm/msm/msm_drv.h > index 9f0c184b02a0..7936aa6cad03 100644 > --- a/drivers/gpu/drm/msm/msm_drv.h > +++ b/drivers/gpu/drm/msm/msm_drv.h > @@ -548,7 +548,7 @@ static inline unsigned long timeout_to_jiffies(const ktime_t *timeout) > remaining_jiffies = ktime_divns(rem, NSEC_PER_SEC / HZ); > } > > - return clamp(remaining_jiffies, 0LL, (s64)INT_MAX); > + return clamp(remaining_jiffies, 1LL, (s64)INT_MAX); > } > > /* Driver helpers */
On Tue, Mar 28, 2023 at 8:28 AM Dmitry Baryshkov <dmitry.baryshkov@linaro.org> wrote: > > On 25/03/2023 00:00, Rob Clark wrote: > > From: Rob Clark <robdclark@chromium.org> > > > > If userspace asked for a timeout greater than zero, but less than a > > jiffy, they clearly weren't planning on spinning. So it is better > > to round up to one. > > > > This fixes an issue with supertuxkart that was (for some reason) > > spinning on a gl sync with 1ms timeout. CPU time for a demo lap > > drops from: > > > > 15.83user 20.98system 0:47.46elapsed 77%CPU > > > > to: > > > > 8.84user 2.30system 0:46.67elapsed 23%CPU > > Interesting. We potentially increased the timeout, but the overall > (elapsed) time has decreased. Nevertheless: There is some randomness from run to run so small variations in total --profile-laps=N time are normal. So I wouldn't read too much into that, compared to %CPU. This shouldn't really change how long it takes for the fence to signal, as much as just prevent the CPU from busy looping until the fence does signal ;-) (In theory the CPU busy looping could cause GPU thermal throttling, but I don't think that was happening in this case.) > Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org> thx > > > > Signed-off-by: Rob Clark <robdclark@chromium.org> > > --- > > drivers/gpu/drm/msm/msm_drv.h | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/drivers/gpu/drm/msm/msm_drv.h b/drivers/gpu/drm/msm/msm_drv.h > > index 9f0c184b02a0..7936aa6cad03 100644 > > --- a/drivers/gpu/drm/msm/msm_drv.h > > +++ b/drivers/gpu/drm/msm/msm_drv.h > > @@ -548,7 +548,7 @@ static inline unsigned long timeout_to_jiffies(const ktime_t *timeout) > > remaining_jiffies = ktime_divns(rem, NSEC_PER_SEC / HZ); > > } > > > > - return clamp(remaining_jiffies, 0LL, (s64)INT_MAX); > > + return clamp(remaining_jiffies, 1LL, (s64)INT_MAX); > > } > > > > /* Driver helpers */ > > -- > With best wishes > Dmitry >
On Fri, 24 Mar 2023 15:00:13 -0700, Rob Clark wrote: > If userspace asked for a timeout greater than zero, but less than a > jiffy, they clearly weren't planning on spinning. So it is better > to round up to one. > > This fixes an issue with supertuxkart that was (for some reason) > spinning on a gl sync with 1ms timeout. CPU time for a demo lap > drops from: > > [...] Applied, thanks! [1/1] drm/msm: Avoid rounding down to zero jiffies https://gitlab.freedesktop.org/lumag/msm/-/commit/a5c5593477b0 Best regards,
diff --git a/drivers/gpu/drm/msm/msm_drv.h b/drivers/gpu/drm/msm/msm_drv.h index 9f0c184b02a0..7936aa6cad03 100644 --- a/drivers/gpu/drm/msm/msm_drv.h +++ b/drivers/gpu/drm/msm/msm_drv.h @@ -548,7 +548,7 @@ static inline unsigned long timeout_to_jiffies(const ktime_t *timeout) remaining_jiffies = ktime_divns(rem, NSEC_PER_SEC / HZ); } - return clamp(remaining_jiffies, 0LL, (s64)INT_MAX); + return clamp(remaining_jiffies, 1LL, (s64)INT_MAX); } /* Driver helpers */