| Message ID | 20241220060009.507297-1-namhyung@kernel.org (mailing list archive) |
|---|---|
| Headers | show |
| Series | perf lock contention: Symbolize locks using slab cache names | expand |
On Thu, Dec 19, 2024 at 10:00:05PM -0800, Namhyung Kim wrote: > Hello, > > This is to support symbolization of dynamic locks using slab > allocator's metadata. The kernel support is merged to v6.13. > > 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. > > v3 changes) > > * fix build error with GEN_VMLINUX_H=1 (Arnaldo) Thanks, applied to perf-tools-next, - Arnaldo > * update comment to explain slab cache ID (Vlastimil) > * add Ian's Acked-by > > v2) https://lore.kernel.org/linux-perf-users/20241108061500.2698340-1-namhyung@kernel.org > > * don't use libbpf_get_error() (Andrii) > > v1) https://lore.kernel.org/linux-perf-users/20241105172635.2463800-1-namhyung@kernel.org > > With this change, it can show locks in a slab object like below. I > added "&" sign to distinguish them from global locks. > > # 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-v3' 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 | 95 +++++++++++- > 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, 292 insertions(+), 7 deletions(-) > > -- > 2.47.1.613.gc27f4b7a9f-goog
Hello, This is to support symbolization of dynamic locks using slab allocator's metadata. The kernel support is merged to v6.13. 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. v3 changes) * fix build error with GEN_VMLINUX_H=1 (Arnaldo) * update comment to explain slab cache ID (Vlastimil) * add Ian's Acked-by v2) https://lore.kernel.org/linux-perf-users/20241108061500.2698340-1-namhyung@kernel.org * don't use libbpf_get_error() (Andrii) v1) https://lore.kernel.org/linux-perf-users/20241105172635.2463800-1-namhyung@kernel.org With this change, it can show locks in a slab object like below. I added "&" sign to distinguish them from global locks. # 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-v3' 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 | 95 +++++++++++- 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, 292 insertions(+), 7 deletions(-)