From: Alexei Starovoitov Date: Wed, 19 Feb 2020 22:37:36 +0000 (-0800) Subject: Merge branch 'bpf_read_branch_records' X-Git-Tag: v5.15~4200^2~372^2~7 X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=03aa39558e74649b8ad19b2a3988a22bef23a517;p=platform%2Fkernel%2Flinux-starfive.git Merge branch 'bpf_read_branch_records' Daniel Xu says: ==================== Branch records are a CPU feature that can be configured to record certain branches that are taken during code execution. This data is particularly interesting for profile guided optimizations. perf has had branch record support for a while but the data collection can be a bit coarse grained. We (Facebook) have seen in experiments that associating metadata with branch records can improve results (after postprocessing). We generally use bpf_probe_read_*() to get metadata out of userspace. That's why bpf support for branch records is useful. Aside from this particular use case, having branch data available to bpf progs can be useful to get stack traces out of userspace applications that omit frame pointers. Changes in v8: - Use globals instead of perf buffer - Call test_perf_branches__detach() before destroying skeleton - Fix typo in docs Changes in v7: - Const-ify and static-ify local var - Documentation formatting Changes in v6: - Move #ifdef a little to avoid unused variable warnings on !x86 - Test negative condition in selftest (-EINVAL on improperly configured perf event) - Skip positive condition selftest on setups that don't support branch records Changes in v5: - Rename bpf_perf_prog_read_branches() -> bpf_read_branch_records() - Rename BPF_F_GET_BR_SIZE -> BPF_F_GET_BRANCH_RECORDS_SIZE - Squash tools/ bpf.h sync into selftest commit Changes in v4: - Add BPF_F_GET_BR_SIZE flag - Return -ENOENT on unsupported architectures - Only accept initialized memory in helper - Check buffer size is multiple of sizeof(struct perf_branch_entry) - Use bpf skeleton in selftest - Add commit messages - Spelling and formatting Changes in v3: - Document filling unused buffer with zero - Formatting fixes - Rebase Changes in v2: - Change to a bpf helper instead of context access - Avoid mentioning Intel specific things ==================== Signed-off-by: Alexei Starovoitov --- 03aa39558e74649b8ad19b2a3988a22bef23a517