Hi Thomas, On Fri, Aug 09, 2019 at 04:12:29PM +0800, Rong Chen wrote: > Hi, > > >>Actually we run the benchmark as a background process, do we need to > >>disable the cursor and test again? > >There's a worker thread that updates the display from the shadow buffer. > >The blinking cursor periodically triggers the worker thread, but the > >actual update is just the size of one character. > > > >The point of the test without output is to see if the regression comes > >from the buffer update (i.e., the memcpy from shadow buffer to VRAM), or > >from the worker thread. If the regression goes away after disabling the > >blinking cursor, then the worker thread is the problem. If it already > >goes away if there's simply no output from the test, the screen update > >is the problem. On my machine I have to disable the blinking cursor, so > >I think the worker causes the performance drop. > > We disabled redirecting stdout/stderr to /dev/kmsg, and the regression is > gone. > > commit: > f1f8555dfb9 drm/bochs: Use shadow buffer for bochs framebuffer console > 90f479ae51a drm/mgag200: Replace struct mga_fbdev with generic framebuffer > emulation > > f1f8555dfb9a70a2 90f479ae51afa45efab97afdde testcase/testparams/testbox > ---------------- -------------------------- --------------------------- > %stddev change %stddev > \ | \ > 43785 44481 > vm-scalability/300s-8T-anon-cow-seq-hugetlb/lkp-knm01 > 43785 44481 GEO-MEAN vm-scalability.median Till now, from Rong's tests: 1. Disabling cursor blinking doesn't cure the regression. 2. Disabling printint test results to console can workaround the regression. Also if we set the perfer_shadown to 0, the regression is also gone. --- a/drivers/gpu/drm/mgag200/mgag200_main.c +++ b/drivers/gpu/drm/mgag200/mgag200_main.c @@ -167,7 +167,7 @@ int mgag200_driver_load(struct drm_device *dev, unsigned long flags) dev->mode_config.preferred_depth = 16; else dev->mode_config.preferred_depth = 32; - dev->mode_config.prefer_shadow = 1; + dev->mode_config.prefer_shadow = 0; And from the perf data, one obvious difference is good case don't call drm_fb_helper_dirty_work(), while bad case calls. Thanks, Feng > Best Regards, > Rong Chen _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
