[0/4] perf lock contention: Improve lock symbol display (v1)

  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.

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.

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
  

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.
> 
> 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
>
  

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
  

Hi Arnaldo,

On Tue, Mar 14, 2023 at 5:23 AM Arnaldo Carvalho de Melo
<acme@kernel.org> wrote:
>
> 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]$

This looks really cool! especially.

I'm especially interested in adding super_block and kernfs_root.
Let me see how I can add them.

Thanks,
Namhyung