Hi Am 09.03.22 um 12:55 schrieb Dmitry Osipenko:
Hello, On 3/9/22 11:59, Thomas Zimmermann wrote:Hi Am 08.03.22 um 14:17 schrieb Dmitry Osipenko:Hello, This patchset introduces memory shrinker for the VirtIO-GPU DRM driver. During OOM, the shrinker will release BOs that are marked as "not needed" by userspace using the new madvise IOCTL. The userspace in this case is the Mesa VirGL driver, it will mark the cached BOs as "not needed", allowing kernel driver to release memory of the cached shmem BOs on lowmem situations, preventing OOM kills.Virtio-gpu is build on top of GEM shmem helpers. I have a prototype patchset that adds a shrinker to these helpers. If you want to go further, you could implement something like that instead. Panfrost and lima also have their own shrinker and could certainly be converted to the gem-shmem shrinker.I had a thought that it could be possible to unify shrinkers into a common DRM framework. Could you please give me a link to yours prototype patchset?
I uploaded the patches to https://gitlab.freedesktop.org/tzimmermann/linux/-/commits/gem-shmem-cached-mappingsit's incomplete and un-debugged, but it shows what needs to be done. It has the infrastructure, but lacks the changes to the GEM shmem code.
The reason for this work is to keep GEM shmem pages mapped and allocated even while the BO is neither mapped nor pinned. As it is now, GEM SHMEM creates and releases pages on each pin and unpin, and maps and unmaps memory ranges on each vmap and vunmap. It's all wasteful. Only the first pin and vmap calls should establish pages and mappings and only the purge and free functions should release them.
The patchset adds new helpers for BO purging to struct drm_gem_object_funcs. With this, I think it might be possible to have one global DRM shrinker and let it handle all BOs; independent of each BO's memory manager.
Best regards Thomas -- Thomas Zimmermann Graphics Driver Developer SUSE Software Solutions Germany GmbH Maxfeldstr. 5, 90409 Nürnberg, Germany (HRB 36809, AG Nürnberg) Geschäftsführer: Ivo Totev
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