Em Mon, Mar 13, 2023 at 06:45:53PM -0300, Arnaldo Carvalho de Melo escreveu: > Em Mon, Mar 13, 2023 at 01:48:21PM -0700, Namhyung Kim escreveu: > > Hello, > > > > This patchset improves the symbolization of locks for -l/--lock-addr mode. > > As of now it only shows global lock symbols present in the kallsyms. But > > we can add some more lock symbols by traversing pointers in the BPF program. > > > > For example, mmap_lock can be reached from the mm_struct of the current task > > (task_struct->mm->mmap_lock) and we can compare the address of the give lock > > with it. Similarly I've added 'siglock' for current->sighand->siglock. Hey, we can go a bit further by using something like pahole's --expand_types and --expand_pointers and play iterating a type members and looking for locks, like: ⬢[acme@toolbox pahole]$ pahole task_struct | grep spinlock_t spinlock_t alloc_lock; /* 3280 4 */ raw_spinlock_t pi_lock; /* 3284 4 */ seqcount_spinlock_t mems_allowed_seq; /* 3616 4 */ ⬢[acme@toolbox pahole]$ Expand points will find mmap_lock: ⬢[acme@toolbox pahole]$ pahole --expand_pointers -C task_struct | grep -B10 mmap_lock } *pgd; atomic_t membarrier_state; atomic_t mm_users; atomic_t mm_count; /* XXX 4 bytes hole, try to pack */ atomic_long_t pgtables_bytes; int map_count; spinlock_t page_table_lock; struct rw_semaphore mmap_lock; ^C ⬢[acme@toolbox pahole]$ ITs just too much expansion to see task_struct->mm, but it is there, of course: ⬢[acme@toolbox pahole]$ pahole mm_struct | grep mmap_lock struct rw_semaphore mmap_lock; /* 120 40 */ ⬢[acme@toolbox pahole]$ Also: ⬢[acme@toolbox pahole]$ pahole --contains rw_semaphore address_space signal_struct key inode super_block quota_info user_namespace blocking_notifier_head backing_dev_info anon_vma tty_struct cpufreq_policy tcf_block ipc_ids autogroup kvm_arch posix_clock listener_list uprobe kernfs_root configfs_fragment ext4_inode_info ext4_group_info btrfs_fs_info extent_buffer btrfs_dev_replace btrfs_space_info btrfs_inode btrfs_block_group tpm_chip ib_device ib_xrcd blk_crypto_profile controller led_classdev cppc_pcc_data dm_snapshot ⬢[acme@toolbox pahole]$ And: ⬢[acme@toolbox pahole]$ pahole --find_pointers_to mm_struct task_struct: mm task_struct: active_mm vm_area_struct: vm_mm flush_tlb_info: mm signal_struct: oom_mm tlb_state: loaded_mm linux_binprm: mm mmu_gather: mm trace_event_raw_xen_mmu_ptep_modify_prot: mm trace_event_raw_xen_mmu_alloc_ptpage: mm trace_event_raw_xen_mmu_pgd: mm trace_event_raw_xen_mmu_flush_tlb_multi: mm trace_event_raw_hyperv_mmu_flush_tlb_multi: mm mmu_notifier: mm mmu_notifier_range: mm sgx_encl_mm: mm rq: prev_mm kvm: mm cpuset_migrate_mm_work: mm mmap_unlock_irq_work: mm delayed_uprobe: mm map_info: mm trace_event_raw_mmap_lock: mm trace_event_raw_mmap_lock_acquire_returned: mm mm_walk: mm make_exclusive_args: mm mmu_interval_notifier: mm mm_slot: mm rmap_item: mm trace_event_raw_mm_khugepaged_scan_pmd: mm trace_event_raw_mm_collapse_huge_page: mm trace_event_raw_mm_collapse_huge_page_swapin: mm mm_slot: mm move_charge_struct: mm userfaultfd_ctx: mm proc_maps_private: mm remap_pfn: mm intel_svm: mm binder_alloc: vma_vm_mm ⬢[acme@toolbox pahole]$ - Arnaldo > > On the other hand, we can traverse some of semi-global locks like per-cpu, > > per-device, per-filesystem and so on. I've added 'rqlock' for each cpu's > > runqueue lock. > > > > It cannot cover all types of locks in the system but it'd be fairly usefule > > if we can add many of often contended locks. I tried to add futex locks > > but it failed to find the __futex_data symbol from BTF. I'm not sure why but > > I guess it's because the struct doesn't have a tag name. > > > > Those locks are added just because they got caught during my test. > > It'd be nice if you suggest which locks to add and how to do that. :) > > I'm thinking if there's a way to track file-based locks (like epoll, etc). > > > > Finally I also added a lock type name after the symbols (if any) so that we > > can get some idea even though it has no symbol. The example output looks > > like below: > > > > $ sudo ./perf lock con -abl -- sleep 1 > > contended total wait max wait avg wait address symbol > > > > 44 6.13 ms 284.49 us 139.28 us ffffffff92e06080 tasklist_lock (rwlock) > > 159 983.38 us 12.38 us 6.18 us ffff8cc717c90000 siglock (spinlock) > > 10 679.90 us 153.35 us 67.99 us ffff8cdc2872aaf8 mmap_lock (rwsem) > > 9 558.11 us 180.67 us 62.01 us ffff8cd647914038 mmap_lock (rwsem) > > 78 228.56 us 7.82 us 2.93 us ffff8cc700061c00 (spinlock) > > 5 41.60 us 16.93 us 8.32 us ffffd853acb41468 (spinlock) > > 10 37.24 us 5.87 us 3.72 us ffff8cd560b5c200 siglock (spinlock) > > 4 11.17 us 3.97 us 2.79 us ffff8d053ddf0c80 rq_lock (spinlock) > > 1 7.86 us 7.86 us 7.86 us ffff8cd64791404c (spinlock) > > 1 4.13 us 4.13 us 4.13 us ffff8d053d930c80 rq_lock (spinlock) > > 7 3.98 us 1.67 us 568 ns ffff8ccb92479440 (mutex) > > 2 2.62 us 2.33 us 1.31 us ffff8cc702e6ede0 (rwlock) > > > > The tasklist_lock is global so it's from the kallsyms. But others like > > siglock, mmap_lock and rq_lock are from the BPF. > > Beautiful :-) > > And the csets are _so_ small and demonstrate techniques that should be > used in more and more tools. > > Applied, testing. > > - Arnaldo > > > You get get the code at 'perf/lock-symbol-v1' branch in > > > > git://git.kernel.org/pub/scm/linux/kernel/git/namhyung/linux-perf.git > > > > Thanks, > > Namhyung > > > > Namhyung Kim (4): > > perf lock contention: Track and show mmap_lock with address > > perf lock contention: Track and show siglock with address > > perf lock contention: Show per-cpu rq_lock with address > > perf lock contention: Show lock type with address > > > > tools/perf/builtin-lock.c | 46 +++++++---- > > tools/perf/util/bpf_lock_contention.c | 35 ++++++++- > > .../perf/util/bpf_skel/lock_contention.bpf.c | 77 +++++++++++++++++++ > > tools/perf/util/bpf_skel/lock_data.h | 14 ++++ > > 4 files changed, 152 insertions(+), 20 deletions(-) > > > > > > base-commit: b8fa3e3833c14151a47ebebbc5427dcfe94bb407 > > -- > > 2.40.0.rc1.284.g88254d51c5-goog > > > > -- > > - Arnaldo -- - Arnaldo
