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Hi Thomas, On 9/4/2019 4:43 PM, Thomas Zimmermann
wrote:
Hi Am 04.09.19 um 10:35 schrieb Feng Tang: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.There are several ways of disabling the cursor. On my test system, I entered tput civis before the test and got better performance. Did you try this as well? There's no obvious change on our system. Best Regards, Rong Chen Best regards ThomasThanks, FengIn 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". -DanielBest regards ThomasThanks, FengBest 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 |
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