On Tue, Mar 08, 2011 at 08:24:26AM +1000, Ben Skeggs wrote: > On Mon, 2011-03-07 at 18:18 +0000, Maarten Maathuis wrote: > > On Fri, Mar 4, 2011 at 4:49 PM, Marcin Slusarz <[email protected]> > > 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 <[email protected]> > > >> --- > > >> 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 > > > _______________________________________________ > > > Nouveau mailing list > > > [email protected] > > > http://lists.freedesktop.org/mailman/listinfo/nouveau > > > > > > > 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 :-) > Ah sorry, I have actually looked at this quite a while back but came to > no solid conclusion. > > While yes, I did see some minor performance improvement from it, I also > notice that now we once again get 100% CPU usage while an app is waiting > for the GPU a lot..
It's not "minor" performance improvement: without this patch (FPS): nexuiz: 53 wop: 181 tremulous: 157 wsw0.5: 89 glxgears: 730 with: nexuiz: 63 (+18%) wop: 248 (+37%) tremulous: 156 (-0.6%) wsw0.5: 91 (+2%) glxgears: 1054 (+44%) Ok, so you are worried about CPU usage... Let's see what will happen if I remove spinning added by "drm/nouveau: Spin for a bit in nouveau_fence_wait() before yielding the CPU". reduced version (attached): nexuiz: 62 wop: 248 trem: 157 wsw0.5: 90 glxgears: 1055 Good enough? --- From: Marcin Slusarz <[email protected]> Subject: [PATCH] drm/nouveau: fix __nouveau_fence_wait performance regression 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. Additionally, remove spinning (added by "drm/nouveau: Spin for a bit in nouveau_fence_wait() before yielding the CPU"), because it's not needed anymore. Signed-off-by: Marcin Slusarz <[email protected]> --- drivers/gpu/drm/nouveau/nouveau_fence.c | 11 ++++++++--- 1 files changed, 8 insertions(+), 3 deletions(-) diff --git a/drivers/gpu/drm/nouveau/nouveau_fence.c b/drivers/gpu/drm/nouveau/nouveau_fence.c index a244702..010243b 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" @@ -229,9 +232,11 @@ 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; + 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; @@ -243,8 +248,8 @@ __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); + if (lazy) + schedule_hrtimeout(&t, HRTIMER_MODE_REL); if (intr && signal_pending(current)) { ret = -ERESTARTSYS; -- 1.7.4.rc3 _______________________________________________ Nouveau mailing list [email protected] http://lists.freedesktop.org/mailman/listinfo/nouveau
