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Message-ID: <Z04dWxBBEfcXK8z5@google.com>
Date: Mon, 2 Dec 2024 12:49:31 -0800
From: Namhyung Kim <namhyung@...nel.org>
To: Chun-Tse Shao <ctshao@...gle.com>
Cc: linux-kernel@...r.kernel.org, peterz@...radead.org, mingo@...hat.com,
acme@...nel.org, mark.rutland@....com,
alexander.shishkin@...ux.intel.com, jolsa@...nel.org,
irogers@...gle.com, adrian.hunter@...el.com,
kan.liang@...ux.intel.com, linux-perf-users@...r.kernel.org
Subject: Re: [PATCH v3 2/2] perf lock: Fix parse_lock_type which only
retrieve one lock flag
Hello,
On Tue, Nov 26, 2024 at 01:22:54PM -0800, Chun-Tse Shao wrote:
> `parse_lock_type` can only add the first lock flag in `lock_type_table`
> given input `str`. For example, for `Y rwlock`, it only adds `rwlock:R`
> into this perf session. Another example is for `-Y mutex`, it only adds
> the mutex without `LCB_F_SPIN` flag. The patch fixes this issue, makes
> sure both `rwlock:R` and `rwlock:W` will be added with `-Y rwlock`, and
> so on.
>
> Testing:
> $ ./perf lock con -ab -Y mutex,rwlock -- perf bench sched pipe
> # Running 'sched/pipe' benchmark:
> # Executed 1000000 pipe operations between two processes
>
> Total time: 8.425 [sec]
>
> 8.425402 usecs/op
> 118688 ops/sec
> contended total wait max wait avg wait type caller
>
> 194 1.68 ms 44.16 us 8.66 us mutex pipe_read+0x57
> 10 423.03 us 44.27 us 42.30 us rwlock:W do_exit+0x365
> 54 254.67 us 58.87 us 4.72 us mutex pipe_write+0x50
> 21 146.64 us 11.54 us 6.98 us mutex pipe_read+0x282
> 10 141.27 us 20.62 us 14.13 us rwlock:W release_task+0x6f
> 5 58.92 us 16.37 us 11.78 us mutex do_epoll_wait+0x24d
> 3 29.81 us 17.66 us 9.94 us mutex do_epoll_ctl+0x6c1
> 4 26.82 us 11.02 us 6.70 us mutex do_epoll_wait+0x24d
> 2 18.32 us 12.49 us 9.16 us rwlock:W do_epoll_wait+0x255
> 1 11.34 us 11.34 us 11.34 us rwlock:W ep_done_scan+0x2d
> 1 11.02 us 11.02 us 11.02 us rwlock:R mm_update_next_owner+0x4e
> 1 10.60 us 10.60 us 10.60 us rwlock:W do_epoll_ctl+0xb65
> 1 9.90 us 9.90 us 9.90 us rwlock:W do_exit+0x365
>
> Fixes: d783ea8f62c4 ("perf lock contention: Simplify parse_lock_type()")
I think it won't apply to earlier kernels because you changed the field
names in the previous commit. I think you can switch the order of the
commits so that we can have the fix first.
> Signed-off-by: Chun-Tse Shao <ctshao@...gle.com>
> ---
> tools/perf/builtin-lock.c | 68 ++++++++++++++++++++++++++-------------
> 1 file changed, 45 insertions(+), 23 deletions(-)
>
> diff --git a/tools/perf/builtin-lock.c b/tools/perf/builtin-lock.c
> index c528aff1c9d5..c1870c287580 100644
> --- a/tools/perf/builtin-lock.c
> +++ b/tools/perf/builtin-lock.c
> @@ -1622,19 +1622,6 @@ static const char *get_type_lock_name(unsigned int flags)
> return "unknown";
> }
>
> -static unsigned int get_type_flag(const char *str)
> -{
> - for (unsigned int i = 0; i < ARRAY_SIZE(lock_type_table); i++) {
> - if (!strcmp(lock_type_table[i].flags_name, str))
> - return lock_type_table[i].flags;
> - }
> - for (unsigned int i = 0; i < ARRAY_SIZE(lock_type_table); i++) {
> - if (!strcmp(lock_type_table[i].lock_name, str))
> - return lock_type_table[i].flags;
> - }
> - return UINT_MAX;
> -}
> -
> static void lock_filter_finish(void)
> {
> zfree(&filters.types);
> @@ -2356,29 +2343,64 @@ static int parse_lock_type(const struct option *opt __maybe_unused, const char *
> int unset __maybe_unused)
> {
> char *s, *tmp, *tok;
> - int ret = 0;
>
> s = strdup(str);
> if (s == NULL)
> return -1;
>
> for (tok = strtok_r(s, ", ", &tmp); tok; tok = strtok_r(NULL, ", ", &tmp)) {
> - unsigned int flags = get_type_flag(tok);
> + bool found = false;
>
> - if (flags == -1U) {
> - pr_err("Unknown lock flags: %s\n", tok);
> - ret = -1;
> - break;
> + /* `tok` is a flags name if it contains ':'. */
> + if (strchr(tok, ':')) {
> + for (unsigned int i = 0; i < ARRAY_SIZE(lock_type_table); i++) {
> + if (!strcmp(lock_type_table[i].flags_name, tok) &&
> + add_lock_type(lock_type_table[i].flags)) {
> + found = true;
> + break;
> + }
> + }
> +
> + if (!found) {
> + pr_err("Unknown lock flags name: %s\n", tok);
> + free(s);
> + return -1;
> + }
> +
> + continue;
> }
>
> - if (!add_lock_type(flags)) {
> - ret = -1;
> - break;
> + /*
> + * Otherwise `tok` is a lock name.
> + * Single lock name could contain multiple flags.
> + */
> + /*
> + * By documentation, `percpu-rwmem` should be `pcpu-sem`.
> + * For backward compatibility, we replace `pcpu-sem` with `percpu-rwmem`.
> + */
> + if (!strcmp(tok, "pcpu-sem"))
> + tok = (char *)"percpu-rwsem";
I think it's better to split the pcpu-sem part into a separate commit as
it fixes a different issue. Also you'd better merge the block commits.
Thanks,
Namhyung
> +
> + for (unsigned int i = 0; i < ARRAY_SIZE(lock_type_table); i++) {
> + if (!strcmp(lock_type_table[i].lock_name, tok)) {
> + if (add_lock_type(lock_type_table[i].flags)) {
> + found = true;
> + } else {
> + free(s);
> + return -1;
> + }
> + }
> + }
> +
> + if (!found) {
> + pr_err("Unknown lock name: %s\n", tok);
> + free(s);
> + return -1;
> }
> }
>
> free(s);
> - return ret;
> + return 0;
> }
>
> static bool add_lock_addr(unsigned long addr)
> --
> 2.47.0.338.g60cca15819-goog
>
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