On Mon, Nov 11, 2024 at 11:46:37AM -0800, Ian Rogers wrote: > On Thu, Nov 7, 2024 at 10:15 PM Namhyung Kim <namhyung@xxxxxxxxxx> wrote: > > > > Hello, > > > > This is to support symbolization of dynamic locks using slab > > allocator's metadata. The kernel support is in the bpf-next tree now. > > > > It provides the new "kmem_cache" BPF iterator and "bpf_get_kmem_cache" > > kfunc to get the information from an address. The feature detection is > > done using BTF type info and it won't have any effect on old kernels. > > > > v2 changes) > > > > * don't use libbpf_get_error() (Andrii) > > > > v1) https://lore.kernel.org/linux-perf-users/20241105172635.2463800-1-namhyung@xxxxxxxxxx > > > > With this change, it can show locks in a slab object like below. I > > added "&" sign to distinguish them from global locks. > > I know the & is intentional but I worry it could later complicate > parsing of filters. Perhaps @ is a viable alternative. Other than > that: > > Acked-by: Ian Rogers <irogers@xxxxxxxxxx> Thanks for the review! I don't think it clashes with BPF sample filters which works on sample data generated from a perf_event. Technically this command doesn't use perf_event and just attaches the BPF program to tracepoint directly. Also sample filters don't use '&' symbol in the syntax as of now. :) Thanks, Namhyung > > > # perf lock con -abl sleep 1 > > contended total wait max wait avg wait address symbol > > > > 2 1.95 us 1.77 us 975 ns ffff9d5e852d3498 &task_struct (mutex) > > 1 1.18 us 1.18 us 1.18 us ffff9d5e852d3538 &task_struct (mutex) > > 4 1.12 us 354 ns 279 ns ffff9d5e841ca800 &kmalloc-cg-512 (mutex) > > 2 859 ns 617 ns 429 ns ffffffffa41c3620 delayed_uprobe_lock (mutex) > > 3 691 ns 388 ns 230 ns ffffffffa41c0940 pack_mutex (mutex) > > 3 421 ns 164 ns 140 ns ffffffffa3a8b3a0 text_mutex (mutex) > > 1 409 ns 409 ns 409 ns ffffffffa41b4cf8 tracepoint_srcu_srcu_usage (mutex) > > 2 362 ns 239 ns 181 ns ffffffffa41cf840 pcpu_alloc_mutex (mutex) > > 1 220 ns 220 ns 220 ns ffff9d5e82b534d8 &signal_cache (mutex) > > 1 215 ns 215 ns 215 ns ffffffffa41b4c28 tracepoint_srcu_srcu_usage (mutex) > > > > The first two were from "task_struct" slab cache. It happened to > > match with the type name of object but there's no guarantee. We need > > to add type info to slab cache to resolve the lock inside the object. > > Anyway, the third one has no dedicated slab cache and was allocated by > > kmalloc. > > > > Those slab objects can be used to filter specific locks using -L or > > --lock-filter option. (It needs quotes to avoid special handling in > > the shell). > > > > # perf lock con -ab -L '&task_struct' sleep 1 > > contended total wait max wait avg wait type caller > > > > 1 25.10 us 25.10 us 25.10 us mutex perf_event_exit_task+0x39 > > 1 21.60 us 21.60 us 21.60 us mutex futex_exit_release+0x21 > > 1 5.56 us 5.56 us 5.56 us mutex futex_exec_release+0x21 > > > > The code is available at 'perf/lock-slab-v2' branch in my tree > > > > git://git.kernel.org/pub/scm/linux/kernel/git/namhyung/linux-perf.git > > > > Thanks, > > Namhyung > > > > > > Namhyung Kim (4): > > perf lock contention: Add and use LCB_F_TYPE_MASK > > perf lock contention: Run BPF slab cache iterator > > perf lock contention: Resolve slab object name using BPF > > perf lock contention: Handle slab objects in -L/--lock-filter option > > > > tools/perf/builtin-lock.c | 39 ++++- > > tools/perf/util/bpf_lock_contention.c | 140 +++++++++++++++++- > > .../perf/util/bpf_skel/lock_contention.bpf.c | 70 ++++++++- > > tools/perf/util/bpf_skel/lock_data.h | 15 +- > > tools/perf/util/bpf_skel/vmlinux/vmlinux.h | 8 + > > tools/perf/util/lock-contention.h | 2 + > > 6 files changed, 267 insertions(+), 7 deletions(-) > > > > -- > > 2.47.0.277.g8800431eea-goog > >
