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Message-ID: <Z0VljcVm4ni-lJrE@google.com>
Date: Mon, 25 Nov 2024 22:07:09 -0800
From: Namhyung Kim <namhyung@...nel.org>
To: Chun-Tse Shao <ctshao@...gle.com>
Cc: linux-kernel@...r.kernel.org, Peter Zijlstra <peterz@...radead.org>,
Ingo Molnar <mingo@...hat.com>,
Arnaldo Carvalho de Melo <acme@...nel.org>,
Mark Rutland <mark.rutland@....com>,
Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
Jiri Olsa <jolsa@...hat.com>, Ian Rogers <irogers@...gle.com>
Subject: Re: [PATCH v2] perf lock: Fix parse_lock_type which only retrieve
one lock flag
Hello,
On Fri, Nov 22, 2024 at 12:27:51AM +0000, 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()")
> Signed-off-by: Chun-Tse Shao <ctshao@...gle.com>
> ---
> tools/perf/builtin-lock.c | 93 ++++++++++++++++++++++++++-------------
> 1 file changed, 62 insertions(+), 31 deletions(-)
>
> diff --git a/tools/perf/builtin-lock.c b/tools/perf/builtin-lock.c
> index 062e2b56a2ab..052dbf423efd 100644
> --- a/tools/perf/builtin-lock.c
> +++ b/tools/perf/builtin-lock.c
> @@ -15,6 +15,7 @@
> #include "util/lock-contention.h"
> #include "util/bpf_skel/lock_data.h"
>
> +#include <string.h>
> #include <subcmd/pager.h>
> #include <subcmd/parse-options.h>
> #include "util/trace-event.h"
> @@ -1575,8 +1576,13 @@ static void sort_result(void)
>
> static const struct {
> unsigned int flags;
> - const char *str;
> + /* Name of the lock. */
> const char *name;
I think this is the name of flag or access - read or write.
> + /*
> + * Name of the group this lock belongs to.
> + * For example, both rwlock:R and rwlock:W belong to rwlock.
> + */
> + const char *group;
And this is the name of the lock (type) - rwlock or rwsem.
> } lock_type_table[] = {
> { 0, "semaphore", "semaphore" },
> { LCB_F_SPIN, "spinlock", "spinlock" },
> @@ -1591,42 +1597,38 @@ static const struct {
> { LCB_F_PERCPU | LCB_F_WRITE, "pcpu-sem:W", "percpu-rwsem" },
> { LCB_F_MUTEX, "mutex", "mutex" },
> { LCB_F_MUTEX | LCB_F_SPIN, "mutex", "mutex" },
> - /* alias for get_type_flag() */
> - { LCB_F_MUTEX | LCB_F_SPIN, "mutex-spin", "mutex" },
> };
>
> -static const char *get_type_str(unsigned int flags)
> +static const char *get_type_name(unsigned int flags)
> {
> flags &= LCB_F_MAX_FLAGS - 1;
>
> for (unsigned int i = 0; i < ARRAY_SIZE(lock_type_table); i++) {
> if (lock_type_table[i].flags == flags)
> - return lock_type_table[i].str;
> + return lock_type_table[i].name;
> }
> return "unknown";
> }
>
> -static const char *get_type_name(unsigned int flags)
> +static const char *get_type_group(unsigned int flags)
> {
> flags &= LCB_F_MAX_FLAGS - 1;
>
> for (unsigned int i = 0; i < ARRAY_SIZE(lock_type_table); i++) {
> if (lock_type_table[i].flags == flags)
> - return lock_type_table[i].name;
> + return lock_type_table[i].group;
> }
> return "unknown";
> }
>
> -static unsigned int get_type_flag(const char *str)
> +static unsigned int get_type_flags_by_name(const char *name)
> {
> for (unsigned int i = 0; i < ARRAY_SIZE(lock_type_table); i++) {
> - if (!strcmp(lock_type_table[i].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].str, str))
> + if (!strcmp(lock_type_table[i].name, name))
> return lock_type_table[i].flags;
> }
> +
> + pr_err("Unknown lock flags: %s\n", name);
I'm not sure if there will be another caller, but it seems better to
have this error message in the parse function directly.
> return UINT_MAX;
> }
>
> @@ -1732,7 +1734,8 @@ static void print_lock_stat_stdio(struct lock_contention *con, struct lock_stat
>
> switch (aggr_mode) {
> case LOCK_AGGR_CALLER:
> - fprintf(lock_output, " %10s %s\n", get_type_str(st->flags), st->name);
> + fprintf(lock_output, " %10s %s\n",
> + get_type_name(st->flags), st->name);
> break;
> case LOCK_AGGR_TASK:
> pid = st->addr;
> @@ -1742,7 +1745,7 @@ static void print_lock_stat_stdio(struct lock_contention *con, struct lock_stat
> break;
> case LOCK_AGGR_ADDR:
> fprintf(lock_output, " %016llx %s (%s)\n", (unsigned long long)st->addr,
> - st->name, get_type_name(st->flags));
> + st->name, get_type_group(st->flags));
> break;
> case LOCK_AGGR_CGROUP:
> fprintf(lock_output, " %s\n", st->name);
> @@ -1783,7 +1786,8 @@ static void print_lock_stat_csv(struct lock_contention *con, struct lock_stat *s
>
> switch (aggr_mode) {
> case LOCK_AGGR_CALLER:
> - fprintf(lock_output, "%s%s %s", get_type_str(st->flags), sep, st->name);
> + fprintf(lock_output, "%s%s %s",
> + get_type_name(st->flags), sep, st->name);
> if (verbose <= 0)
> fprintf(lock_output, "\n");
> break;
> @@ -1795,7 +1799,7 @@ static void print_lock_stat_csv(struct lock_contention *con, struct lock_stat *s
> break;
> case LOCK_AGGR_ADDR:
> fprintf(lock_output, "%llx%s %s%s %s\n", (unsigned long long)st->addr, sep,
> - st->name, sep, get_type_name(st->flags));
> + st->name, sep, get_type_group(st->flags));
> break;
> case LOCK_AGGR_CGROUP:
> fprintf(lock_output, "%s\n",st->name);
> @@ -2338,41 +2342,68 @@ static bool add_lock_type(unsigned int flags)
> unsigned int *tmp;
>
> tmp = realloc(filters.types, (filters.nr_types + 1) * sizeof(*filters.types));
> - if (tmp == NULL)
> + if (tmp == NULL) {
> + pr_err("Failed to add lock flags: %u\n", flags);
> return false;
> + }
>
> tmp[filters.nr_types++] = flags;
> filters.types = tmp;
> return true;
> }
>
> -static int parse_lock_type(const struct option *opt __maybe_unused, const char *str,
> - int unset __maybe_unused)
> +static int parse_lock_type(const struct option *opt __maybe_unused,
> + const char *str, 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);
> + for (tok = strtok_r(s, ", ", &tmp); tok;
> + tok = strtok_r(NULL, ", ", &tmp)) {
I think you changed this because of the 80 column limit. But I think
it's recently increased to 100 so you don't need to change this line
uncessarily.
Other lines containing actual changes may be accceptable. It's up to
you but I generally prefer smaller changes.
> + bool found = false;
>
> - if (flags == -1U) {
> - pr_err("Unknown lock flags: %s\n", tok);
> - ret = -1;
> - break;
> + /* `tok` is a lock name if it contains ':'. */
> + if (strchr(tok, ':')) {
> + unsigned int flags = get_type_flags_by_name(tok);
> +
> + if (flags == UINT_MAX || !add_lock_type(flags)) {
> + free(s);
> + return -1;
> + }
> + continue;
> }
>
> - if (!add_lock_type(flags)) {
> - ret = -1;
> - break;
> + /* Otherwise look up flags by lock group */
> + /*
> + * 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";
Can you please split this into a separate fix?
Thanks,
Namhyung
> +
> + for (unsigned int i = 0; i < ARRAY_SIZE(lock_type_table); i++) {
> + if (!strcmp(lock_type_table[i].group, tok)) {
> + if (add_lock_type(lock_type_table[i].flags)) {
> + found = true;
> + } else {
> + free(s);
> + return -1;
> + }
> + }
> + }
> +
> + if (!found) {
> + pr_err("Unknown lock flags: %s\n", tok);
> + free(s);
> + return -1;
> }
> }
>
> free(s);
> - return ret;
> + return 0;
> }
>
> static bool add_lock_addr(unsigned long addr)
> --
> 2.47.0.371.ga323438b13-goog
>
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