On Thu, Mar 10, 2022 at 5:16 PM Hao Luo <haoluo@xxxxxxxxxx> wrote: > > On Fri, Feb 25, 2022 at 12:43 PM Pasha Tatashin > <pasha.tatashin@xxxxxxxxxx> wrote: > > > > On 2/23/22 19:05, Hao Luo wrote: > > > For binaries that are statically linked, consecutive stack frames are > > > likely to be in the same VMA and therefore have the same build id. > > > As an optimization for this case, we can cache the previous frame's > > > VMA, if the new frame has the same VMA as the previous one, reuse the > > > previous one's build id. We are holding the MM locks as reader across > > > the entire loop, so we don't need to worry about VMA going away. > > > > > > Tested through "stacktrace_build_id" and "stacktrace_build_id_nmi" in > > > test_progs. > > > > > > Suggested-by: Greg Thelen <gthelen@xxxxxxxxxx> > > > Signed-off-by: Hao Luo <haoluo@xxxxxxxxxx> > > > > Reviewed-by: Pasha Tatashin <pasha.tatashin@xxxxxxxxxx> > > > > An update with performance numbers. Thanks to Blake Jones for > collecting the stats: > > In a production workload, with BPF probes sampling stack trace, we see > the following changes: > > - stack_map_get_build_id_offset() is taking 70% of the time of > __bpf_get_stackid(); it was 80% before. Great, thanks for following up with updated numbers! > > - find_get_page() and find_vma() together are taking 75% of the time > of stack_map_get_build_id_offset(); it was 83% before. > > Note the call chain is > > __bpf_get_stackid() > -> stack_map_get_build_id_offset() > -> find_get_page() > -> find_vma() > > > Thanks, > > Pasha
