Hi Daniel, On Wed, Sep 04, 2019 at 10:11:11AM +0200, Daniel Vetter wrote: > On Wed, Sep 4, 2019 at 8:53 AM Thomas Zimmermann <tzimmermann@xxxxxxx> wrote: > > > > Hi > > > > Am 04.09.19 um 08:27 schrieb Feng Tang: > > >> Thank you for testing. But don't get too excited, because the patch > > >> simulates a bug that was present in the original mgag200 code. A > > >> significant number of frames are simply skipped. That is apparently the > > >> reason why it's faster. > > > > > > Thanks for the detailed info, so the original code skips time-consuming > > > work inside atomic context on purpose. Is there any space to optmise it? > > > If 2 scheduled update worker are handled at almost same time, can one be > > > skipped? > > > > To my knowledge, there's only one instance of the worker. Re-scheduling > > the worker before a previous instance started, will not create a second > > instance. The worker's instance will complete all pending updates. So in > > some way, skipping workers already happens. > > So I think that the most often fbcon update from atomic context is the > blinking cursor. If you disable that one you should be back to the old > performance level I think, since just writing to dmesg is from process > context, so shouldn't change. Hmm, then for the old driver, it should also do the most update in non-atomic context? One other thing is, I profiled that updating a 3MB shadow buffer needs 20 ms, which transfer to 150 MB/s bandwidth. Could it be related with the cache setting of DRM shadow buffer? say the orginal code use a cachable buffer? > > https://unix.stackexchange.com/questions/3759/how-to-stop-cursor-from-blinking > > Bunch of tricks, but tbh I haven't tested them. Thomas has suggested to disable curson by echo 0 > /sys/devices/virtual/graphics/fbcon/cursor_blink We tried that way, and no change for the performance data. Thanks, Feng > > In any case, I still strongly advice you don't print anything to dmesg > or fbcon while benchmarking, because dmesg/printf are anything but > fast, especially if a gpu driver is involved. There's some efforts to > make the dmesg/printk side less painful (untangling the console_lock > from printk), but fundamentally printing to the gpu from the kernel > through dmesg/fbcon won't be cheap. It's just not something we > optimize beyond "make sure it works for emergencies". > -Daniel > > > > > Best regards > > Thomas > > > > > > > > Thanks, > > > Feng > > > > > >> > > >> Best regards > > >> Thomas > > > _______________________________________________ > > > dri-devel mailing list > > > dri-devel@xxxxxxxxxxxxxxxxxxxxx > > > https://lists.freedesktop.org/mailman/listinfo/dri-devel > > > > > > > -- > > Thomas Zimmermann > > Graphics Driver Developer > > SUSE Linux GmbH, Maxfeldstrasse 5, 90409 Nuernberg, Germany > > GF: Felix Imendörffer, Mary Higgins, Sri Rasiah > > HRB 21284 (AG Nürnberg) > > > > _______________________________________________ > > dri-devel mailing list > > dri-devel@xxxxxxxxxxxxxxxxxxxxx > > https://lists.freedesktop.org/mailman/listinfo/dri-devel > > > > -- > Daniel Vetter > Software Engineer, Intel Corporation > +41 (0) 79 365 57 48 - http://blog.ffwll.ch _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
