On Thu, May 8, 2025 at 11:04 PM Christian König <christian.koe...@amd.com> wrote: > > Feel free to add my Acked-by to the patches which don't have my rb yet. > > And ping me when I should upstream this through drm-misc-next, but if you > want to upstream this through some other branch then that is fine with me as > well.
Thanks Christian. Alexei mentioned he was willing to take the series through bpf-next here: https://lore.kernel.org/all/caadnvqlqv-zpoqehk2uwvszorslcjgf7qld76ohguh5-gcs...@mail.gmail.com/ I think it makes sense to send the CONFIG_DMABUF_SYSFS_STATS removal through drm-misc-next though, so I'll resend that as a standalone patch whenever I hear about the next longterm stable release. > > Regards, > Christian. > > On 5/8/25 20:20, T.J. Mercier wrote: > > Until CONFIG_DMABUF_SYSFS_STATS was added [1] it was only possible to > > perform per-buffer accounting with debugfs which is not suitable for > > production environments. Eventually we discovered the overhead with > > per-buffer sysfs file creation/removal was significantly impacting > > allocation and free times, and exacerbated kernfs lock contention. [2] > > dma_buf_stats_setup() is responsible for 39% of single-page buffer > > creation duration, or 74% of single-page dma_buf_export() duration when > > stressing dmabuf allocations and frees. > > > > I prototyped a change from per-buffer to per-exporter statistics with a > > RCU protected list of exporter allocations that accommodates most (but > > not all) of our use-cases and avoids almost all of the sysfs overhead. > > While that adds less overhead than per-buffer sysfs, and less even than > > the maintenance of the dmabuf debugfs_list, it's still *additional* > > overhead on top of the debugfs_list and doesn't give us per-buffer info. > > > > This series uses the existing dmabuf debugfs_list to implement a BPF > > dmabuf iterator, which adds no overhead to buffer allocation/free and > > provides per-buffer info. The list has been moved outside of > > CONFIG_DEBUG_FS scope so that it is always populated. The BPF program > > loaded by userspace that extracts per-buffer information gets to define > > its own interface which avoids the lack of ABI stability with debugfs. > > > > This will allow us to replace our use of CONFIG_DMABUF_SYSFS_STATS, and > > the plan is to remove it from the kernel after the next longterm stable > > release. > > > > [1] > > https://lore.kernel.org/linux-media/20201210044400.1080308-1-hri...@google.com > > [2] > > https://lore.kernel.org/all/20220516171315.2400578-1-tjmerc...@google.com > > > > v1: > > https://lore.kernel.org/all/20250414225227.3642618-1-tjmerc...@google.com > > v1 -> v2: > > Make the DMA buffer list independent of CONFIG_DEBUG_FS per Christian König > > Add CONFIG_DMA_SHARED_BUFFER check to kernel/bpf/Makefile per kernel test > > robot > > Use BTF_ID_LIST_SINGLE instead of BTF_ID_LIST_GLOBAL_SINGLE per Song Liu > > Fixup comment style, mixing code/declarations, and use ASSERT_OK_FD in > > selftest per Song Liu > > Add BPF_ITER_RESCHED feature to bpf_dmabuf_reg_info per Alexei Starovoitov > > Add open-coded iterator and selftest per Alexei Starovoitov > > Add a second test buffer from the system dmabuf heap to selftests > > Use the BPF program we'll use in production for selftest per Alexei > > Starovoitov > > https://r.android.com/c/platform/system/bpfprogs/+/3616123/2/dmabufIter.c > > > > https://r.android.com/c/platform/system/memory/libmeminfo/+/3614259/1/libdmabufinfo/dmabuf_bpf_stats.cpp > > v2: > > https://lore.kernel.org/all/20250504224149.1033867-1-tjmerc...@google.com > > v2 -> v3: > > Rebase onto bpf-next/master > > Move get_next_dmabuf() into drivers/dma-buf/dma-buf.c, along with the > > new get_first_dmabuf(). This avoids having to expose the dmabuf list > > and mutex to the rest of the kernel, and keeps the dmabuf mutex > > operations near each other in the same file. (Christian König) > > Add Christian's RB to dma-buf: Rename debugfs symbols > > Drop RFC: dma-buf: Remove DMA-BUF statistics > > v3: > > https://lore.kernel.org/all/20250507001036.2278781-1-tjmerc...@google.com > > v3 -> v4: > > Fix selftest BPF program comment style (not kdoc) per Alexei Starovoitov > > Fix dma-buf.c kdoc comment style per Alexei Starovoitov > > Rename get_first_dmabuf / get_next_dmabuf to dma_buf_iter_begin / > > dma_buf_iter_next per Christian König > > Add Christian's RB to bpf: Add dmabuf iterator > > > > T.J. Mercier (5): > > dma-buf: Rename debugfs symbols > > bpf: Add dmabuf iterator > > bpf: Add open coded dmabuf iterator > > selftests/bpf: Add test for dmabuf_iter > > selftests/bpf: Add test for open coded dmabuf_iter > > > > drivers/dma-buf/dma-buf.c | 98 +++++-- > > include/linux/dma-buf.h | 4 +- > > kernel/bpf/Makefile | 3 + > > kernel/bpf/dmabuf_iter.c | 149 ++++++++++ > > kernel/bpf/helpers.c | 5 + > > .../testing/selftests/bpf/bpf_experimental.h | 5 + > > tools/testing/selftests/bpf/config | 3 + > > .../selftests/bpf/prog_tests/dmabuf_iter.c | 258 ++++++++++++++++++ > > .../testing/selftests/bpf/progs/dmabuf_iter.c | 91 ++++++ > > 9 files changed, 594 insertions(+), 22 deletions(-) > > create mode 100644 kernel/bpf/dmabuf_iter.c > > create mode 100644 tools/testing/selftests/bpf/prog_tests/dmabuf_iter.c > > create mode 100644 tools/testing/selftests/bpf/progs/dmabuf_iter.c > > > > > > base-commit: 43745d11bfd9683abdf08ad7a5cc403d6a9ffd15 >
