On Wed, 4 Sep 2019 at 19:17, Daniel Vetter <daniel@xxxxxxxx> wrote: > > On Wed, Sep 4, 2019 at 10:35 AM Feng Tang <feng.tang@xxxxxxxxx> wrote: > > > > 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? > > Hm, that would indicate the write-combining got broken somewhere. This > should definitely be faster. Also we shouldn't transfer the hole > thing, except when scrolling ... First rule of fbcon usage, you are always effectively scrolling. Also these devices might be on a PCIE 1x piece of wet string, not sure if the numbers reflect that. Dave. _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
