Re: [PATCH v2 2/4] perf trace: Convert syscall_stats to hashmap

From: Ian Rogers
Date: Sun Feb 02 2025 - 02:04:18 EST

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On Wed, Jan 29, 2025 at 7:05 PM Namhyung Kim <namhyung@xxxxxxxxxx> wrote:
>
> It was using a RBtree-based int-list as a hash and a custome resort
> logic for that. As we have hashmap, let's convert to it and add a
> sorting function using an array.

How is a hashmap connected to a sorting function of an array?

> It's also to prepare supporting
> system-wide syscall stats.
>
> No functional changes intended.
>
> Signed-off-by: Namhyung Kim <namhyung@xxxxxxxxxx>
> ---
> tools/perf/builtin-trace.c | 122 ++++++++++++++++++++++++++++---------
> 1 file changed, 93 insertions(+), 29 deletions(-)
>
> diff --git a/tools/perf/builtin-trace.c b/tools/perf/builtin-trace.c
> index 7e0324a2e9182088..1d32ef2b05ae8c1c 100644
> --- a/tools/perf/builtin-trace.c
> +++ b/tools/perf/builtin-trace.c
> @@ -39,6 +39,7 @@
> #include "util/synthetic-events.h"
> #include "util/evlist.h"
> #include "util/evswitch.h"
> +#include "util/hashmap.h"
> #include "util/mmap.h"
> #include <subcmd/pager.h>
> #include <subcmd/exec-cmd.h>
> @@ -63,7 +64,6 @@
> #include "print_binary.h"
> #include "string2.h"
> #include "syscalltbl.h"
> -#include "rb_resort.h"
> #include "../perf.h"
> #include "trace_augment.h"
>
> @@ -1519,17 +1519,55 @@ struct thread_trace {
> struct file *table;
> } files;
>
> - struct intlist *syscall_stats;
> + struct hashmap *syscall_stats;
> };
>
> +static size_t id_hash(long key, void *ctx __maybe_unused)

I find the use of "id" in this code confusing - it is a pre-existing
problem, but you add to it here. I think a more intention revealing
name would be something like system_call_number_hash.

> +{
> + return key;
> +}
> +
> +static bool id_equal(long key1, long key2, void *ctx __maybe_unused)
> +{
> + return key1 == key2;
> +}
> +
> +static struct hashmap *alloc_syscall_stats(void)
> +{
> + struct hashmap *stats = hashmap__new(id_hash, id_equal, NULL);
> +
> + /* just for simpler error check */

What is "just for simpler error check" ?

> + if (IS_ERR(stats))
> + stats = NULL;
> + return stats;
> +}
> +
> +static void delete_syscall_stats(struct hashmap *syscall_stats)
> +{
> + struct hashmap_entry *pos;
> + size_t bkt;
> +
> + if (syscall_stats == NULL)
> + return;
> +
> + hashmap__for_each_entry(syscall_stats, pos, bkt)
> + free(pos->pvalue);
> + hashmap__free(syscall_stats);
> +}
> +
> static struct thread_trace *thread_trace__new(struct trace *trace)
> {
> struct thread_trace *ttrace = zalloc(sizeof(struct thread_trace));
>
> if (ttrace) {
> ttrace->files.max = -1;
> - if (trace->summary)
> - ttrace->syscall_stats = intlist__new(NULL);
> + if (trace->summary) {
> + ttrace->syscall_stats = alloc_syscall_stats();
> + if (ttrace->syscall_stats == NULL) {
> + free(ttrace);
> + ttrace = NULL;

This looks overly indented.

Thanks,
Ian

> + }
> + }
> }
>
> return ttrace;
> @@ -1544,7 +1582,7 @@ static void thread_trace__delete(void *pttrace)
> if (!ttrace)
> return;
>
> - intlist__delete(ttrace->syscall_stats);
> + delete_syscall_stats(ttrace->syscall_stats);
> ttrace->syscall_stats = NULL;
> thread_trace__free_files(ttrace);
> zfree(&ttrace->entry_str);
> @@ -2463,22 +2501,19 @@ struct syscall_stats {
> static void thread__update_stats(struct thread *thread, struct thread_trace *ttrace,
> int id, struct perf_sample *sample, long err, bool errno_summary)
> {
> - struct int_node *inode;
> - struct syscall_stats *stats;
> + struct syscall_stats *stats = NULL;
> u64 duration = 0;
>
> - inode = intlist__findnew(ttrace->syscall_stats, id);
> - if (inode == NULL)
> - return;
> -
> - stats = inode->priv;
> - if (stats == NULL) {
> + if (!hashmap__find(ttrace->syscall_stats, id, &stats)) {
> stats = zalloc(sizeof(*stats));
> if (stats == NULL)
> return;
>
> init_stats(&stats->stats);
> - inode->priv = stats;
> + if (hashmap__add(ttrace->syscall_stats, id, stats) < 0) {
> + free(stats);
> + return;
> + }
> }
>
> if (ttrace->entry_time && sample->time > ttrace->entry_time)
> @@ -4617,18 +4652,45 @@ static size_t trace__fprintf_threads_header(FILE *fp)
> return printed;
> }
>
> -DEFINE_RESORT_RB(syscall_stats, a->msecs > b->msecs,
> +struct syscall_entry {
> struct syscall_stats *stats;
> double msecs;
> int syscall;
> -)
> +};
> +
> +static int entry_cmp(const void *e1, const void *e2)
> {
> - struct int_node *source = rb_entry(nd, struct int_node, rb_node);
> - struct syscall_stats *stats = source->priv;
> + const struct syscall_entry *entry1 = e1;
> + const struct syscall_entry *entry2 = e2;
>
> - entry->syscall = source->i;
> - entry->stats = stats;
> - entry->msecs = stats ? (u64)stats->stats.n * (avg_stats(&stats->stats) / NSEC_PER_MSEC) : 0;
> + return entry1->msecs > entry2->msecs ? -1 : 1;
> +}
> +
> +static struct syscall_entry *thread__sort_stats(struct thread_trace *ttrace)
> +{
> + struct syscall_entry *entry;
> + struct hashmap_entry *pos;
> + unsigned bkt, i, nr;
> +
> + nr = ttrace->syscall_stats->sz;
> + entry = malloc(nr * sizeof(*entry));
> + if (entry == NULL)
> + return NULL;
> +
> + i = 0;
> + hashmap__for_each_entry(ttrace->syscall_stats, pos, bkt) {
> + struct syscall_stats *ss = pos->pvalue;
> + struct stats *st = &ss->stats;
> +
> + entry[i].stats = ss;
> + entry[i].msecs = (u64)st->n * (avg_stats(st) / NSEC_PER_MSEC);
> + entry[i].syscall = pos->key;
> + i++;
> + }
> + assert(i == nr);
> +
> + qsort(entry, nr, sizeof(*entry), entry_cmp);
> + return entry;
> }
>
> static size_t thread__dump_stats(struct thread_trace *ttrace,
> @@ -4636,10 +4698,10 @@ static size_t thread__dump_stats(struct thread_trace *ttrace,
> {
> size_t printed = 0;
> struct syscall *sc;
> - struct rb_node *nd;
> - DECLARE_RESORT_RB_INTLIST(syscall_stats, ttrace->syscall_stats);
> + struct syscall_entry *entries;
>
> - if (syscall_stats == NULL)
> + entries = thread__sort_stats(ttrace);
> + if (entries == NULL)
> return 0;
>
> printed += fprintf(fp, "\n");
> @@ -4648,8 +4710,10 @@ static size_t thread__dump_stats(struct thread_trace *ttrace,
> printed += fprintf(fp, " (msec) (msec) (msec) (msec) (%%)\n");
> printed += fprintf(fp, " --------------- -------- ------ -------- --------- --------- --------- ------\n");
>
> - resort_rb__for_each_entry(nd, syscall_stats) {
> - struct syscall_stats *stats = syscall_stats_entry->stats;
> + for (size_t i = 0; i < ttrace->syscall_stats->sz; i++) {
> + struct syscall_entry *entry = &entries[i];
> + struct syscall_stats *stats = entry->stats;
> +
> if (stats) {
> double min = (double)(stats->stats.min) / NSEC_PER_MSEC;
> double max = (double)(stats->stats.max) / NSEC_PER_MSEC;
> @@ -4660,10 +4724,10 @@ static size_t thread__dump_stats(struct thread_trace *ttrace,
> pct = avg ? 100.0 * stddev_stats(&stats->stats) / avg : 0.0;
> avg /= NSEC_PER_MSEC;
>
> - sc = &trace->syscalls.table[syscall_stats_entry->syscall];
> + sc = &trace->syscalls.table[entry->syscall];
> printed += fprintf(fp, " %-15s", sc->name);
> printed += fprintf(fp, " %8" PRIu64 " %6" PRIu64 " %9.3f %9.3f %9.3f",
> - n, stats->nr_failures, syscall_stats_entry->msecs, min, avg);
> + n, stats->nr_failures, entry->msecs, min, avg);
> printed += fprintf(fp, " %9.3f %9.2f%%\n", max, pct);
>
> if (trace->errno_summary && stats->nr_failures) {
> @@ -4677,7 +4741,7 @@ static size_t thread__dump_stats(struct thread_trace *ttrace,
> }
> }
>
> - resort_rb__delete(syscall_stats);
> + free(entries);
> printed += fprintf(fp, "\n\n");
>
> return printed;
> --
> 2.48.1.262.g85cc9f2d1e-goog
>

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