On 03/14/2018 06:36 PM, Song Liu wrote: >> On Mar 14, 2018, at 10:23 AM, Song Liu <[email protected]> wrote: >> >> Currently, bpf stackmap store address for each entry in the call trace. >> To map these addresses to user space files, it is necessary to maintain >> the mapping from these virtual address to symbols in the binary. Usually, >> the user space profiler (such as perf) has to scan /proc/pid/maps at the >> beginning of profiling, and monitor mmap2() calls afterwards. Given the >> cost of maintaining the address map, this solution is not practical for >> system wide profiling that is always on. >> >> This patch tries to solve this problem with a variation of stackmap. This >> variation is enabled by flag BPF_F_STACK_BUILD_ID. Instead of storing >> addresses, the variation stores ELF file build_id + offset. >> >> Build_id is >> only meaningful for user stack. If a kernel stack is added to a stackmap >> with BPF_F_STACK_BUILD_ID, it will automatically fallback to only store >> ip (status == BPF_STACK_BUILD_ID_IP). > > I forgot to delete the paragraph above. Please let me know if I should > resend (or it can be removed when you apply it).
We can fix it up when applying, no problem. Thanks, Daniel
