perf lock contention: Track and show mmap_lock with address

Sometimes there are severe contentions on the mmap_lock and we want
see it in the -l/--lock-addr output.  However it cannot symbolize
the mmap_lock because it's allocated dynamically without symbols.

Stephane and Hao gave me an idea separately to display mmap_lock by
following the current->mm pointer.  I added a flag to mark mmap_lock
after comparing the lock address so that it can show them differently.
With this change it can show mmap_lock like below:

  $ sudo ./perf lock con -abl -- sleep 10
   contended   total wait     max wait     avg wait            address   symbol
   ...
       16344    312.30 ms      2.22 ms     19.11 us   ffff8cc702595640
       17686    310.08 ms      1.49 ms     17.53 us   ffff8cc7025952c0
           3     84.14 ms     45.79 ms     28.05 ms   ffff8cc78114c478   mmap_lock
        3557     76.80 ms     68.75 us     21.59 us   ffff8cc77ca3af58
           1     68.27 ms     68.27 ms     68.27 ms   ffff8cda745dfd70
           9     54.53 ms      7.96 ms      6.06 ms   ffff8cc7642a48b8   mmap_lock
       14629     44.01 ms     60.00 us      3.01 us   ffff8cc7625f9ca0
        3481     42.63 ms    140.71 us     12.24 us   ffffffff937906ac   vmap_area_lock
       16194     38.73 ms     42.15 us      2.39 us   ffff8cd397cbc560
          11     38.44 ms     10.39 ms      3.49 ms   ffff8ccd6d12fbb8   mmap_lock
           1      5.43 ms      5.43 ms      5.43 ms   ffff8cd70018f0d8
        1674      5.38 ms    422.93 us      3.21 us   ffffffff92e06080   tasklist_lock
         581      4.51 ms    130.68 us      7.75 us   ffff8cc9b1259058
           5      3.52 ms      1.27 ms    703.23 us   ffff8cc754510070
         112      3.47 ms     56.47 us     31.02 us   ffff8ccee38b3120
         381      3.31 ms     73.44 us      8.69 us   ffffffff93790690   purge_vmap_area_lock
         255      3.19 ms     36.35 us     12.49 us   ffff8d053ce30c80

Note that mmap_lock was renamed some time ago and it needs to support
old kernels with a different name 'mmap_sem'.

Suggested-by: Hao Luo <haoluo@google.com>
Suggested-by: Stephane Eranian <eranian@google.com>
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Song Liu <song@kernel.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Waiman Long <longman@redhat.com>
Cc: Will Deacon <will@kernel.org>
Cc: bpf@vger.kernel.org
Link: https://lore.kernel.org/r/20230313204825.2665483-2-namhyung@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
This commit is contained in:
Namhyung Kim 2023-03-13 13:48:22 -07:00 committed by Arnaldo Carvalho de Melo
parent 8d98ca5c02
commit 3ace2435bb
3 changed files with 48 additions and 1 deletions

View File

@ -1663,7 +1663,7 @@ static void print_contention_result(struct lock_contention *con)
break;
case LOCK_AGGR_ADDR:
pr_info(" %016llx %s\n", (unsigned long long)st->addr,
st->name ? : "");
(st->flags & LCD_F_MMAP_LOCK) ? "mmap_lock" : st->name);
break;
default:
break;

View File

@ -92,6 +92,14 @@ struct rw_semaphore___new {
atomic_long_t owner;
} __attribute__((preserve_access_index));
struct mm_struct___old {
struct rw_semaphore mmap_sem;
} __attribute__((preserve_access_index));
struct mm_struct___new {
struct rw_semaphore mmap_lock;
} __attribute__((preserve_access_index));
/* control flags */
int enabled;
int has_cpu;
@ -210,6 +218,36 @@ static inline struct task_struct *get_lock_owner(__u64 lock, __u32 flags)
return task;
}
static inline __u32 check_lock_type(__u64 lock, __u32 flags)
{
struct task_struct *curr;
struct mm_struct___old *mm_old;
struct mm_struct___new *mm_new;
switch (flags) {
case LCB_F_READ: /* rwsem */
case LCB_F_WRITE:
curr = bpf_get_current_task_btf();
if (curr->mm == NULL)
break;
mm_new = (void *)curr->mm;
if (bpf_core_field_exists(mm_new->mmap_lock)) {
if (&mm_new->mmap_lock == (void *)lock)
return LCD_F_MMAP_LOCK;
break;
}
mm_old = (void *)curr->mm;
if (bpf_core_field_exists(mm_old->mmap_sem)) {
if (&mm_old->mmap_sem == (void *)lock)
return LCD_F_MMAP_LOCK;
}
break;
default:
break;
}
return 0;
}
SEC("tp_btf/contention_begin")
int contention_begin(u64 *ctx)
{
@ -320,6 +358,9 @@ int contention_end(u64 *ctx)
.flags = pelem->flags,
};
if (aggr_mode == LOCK_AGGR_ADDR)
first.flags |= check_lock_type(pelem->lock, pelem->flags);
bpf_map_update_elem(&lock_stat, &key, &first, BPF_NOEXIST);
bpf_map_delete_elem(&tstamp, &pid);
return 0;

View File

@ -15,6 +15,12 @@ struct contention_task_data {
char comm[TASK_COMM_LEN];
};
/*
* Upper bits of the flags in the contention_data are used to identify
* some well-known locks which do not have symbols (non-global locks).
*/
#define LCD_F_MMAP_LOCK (1U << 31)
struct contention_data {
u64 total_time;
u64 min_time;