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Message-ID: <CAP-5=fXmAbz7Gp5eCRFYsYu_pZoFNSR+mcJgE6Eu6YewHyLNtg@mail.gmail.com>
Date: Mon, 6 Oct 2025 08:21:12 -0700
From: Ian Rogers <irogers@...gle.com>
To: James Clark <james.clark@...aro.org>
Cc: Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>,
Arnaldo Carvalho de Melo <acme@...nel.org>, Namhyung Kim <namhyung@...nel.org>,
Mark Rutland <mark.rutland@....com>,
Alexander Shishkin <alexander.shishkin@...ux.intel.com>, Jiri Olsa <jolsa@...nel.org>,
Adrian Hunter <adrian.hunter@...el.com>, Leo Yan <leo.yan@....com>,
linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] perf tests: Don't retest sections in "Object code reading"
On Mon, Oct 6, 2025 at 6:11 AM James Clark <james.clark@...aro.org> wrote:
>
> We already only test each kcore map once, but on slow systems
> (particularly with network filesystems) even the non-kcore maps are
> slow. The test can test the same objump output over and over which only
> wastes time. Generalize the skipping mechanism to track all DSOs and
> addresses so that each section is only tested once.
>
> On a fully loaded Arm Juno (simulating a parallel Perf test run) with a
> network filesystem, the original runtime is:
>
> real 1m51.126s
> user 0m19.445s
> sys 1m15.431s
>
> And the new runtime is:
>
> real 0m48.873s
> user 0m8.031s
> sys 0m32.353s
>
> Signed-off-by: James Clark <james.clark@...aro.org>
Reviewed-by: Ian Rogers <irogers@...gle.com>
> ---
> tools/perf/tests/code-reading.c | 119 ++++++++++++++++++++++++++++------------
> 1 file changed, 85 insertions(+), 34 deletions(-)
>
> diff --git a/tools/perf/tests/code-reading.c b/tools/perf/tests/code-reading.c
> index 9c2091310191..4c9fbf6965c4 100644
> --- a/tools/perf/tests/code-reading.c
> +++ b/tools/perf/tests/code-reading.c
> @@ -2,6 +2,7 @@
> #include <errno.h>
> #include <linux/kconfig.h>
> #include <linux/kernel.h>
> +#include <linux/rbtree.h>
> #include <linux/types.h>
> #include <inttypes.h>
> #include <stdlib.h>
> @@ -39,11 +40,64 @@
> #define BUFSZ 1024
> #define READLEN 128
>
> -struct state {
> - u64 done[1024];
> - size_t done_cnt;
> +struct tested_section {
> + struct rb_node rb_node;
> + u64 addr;
> + char path[PATH_MAX];
> };
>
> +static bool tested_code_insert_or_exists(const char *path, u64 addr,
> + struct rb_root *tested_sections)
> +{
> + struct rb_node **node = &tested_sections->rb_node;
> + struct rb_node *parent = NULL;
> + struct tested_section *data;
> +
> + while (*node) {
> + int cmp;
> +
> + parent = *node;
> + data = rb_entry(*node, struct tested_section, rb_node);
> + cmp = strcmp(path, data->path);
> + if (!cmp) {
> + if (addr < data->addr)
> + cmp = -1;
> + else if (addr > data->addr)
> + cmp = 1;
> + else
> + return true; /* already tested */
> + }
> +
> + if (cmp < 0)
> + node = &(*node)->rb_left;
> + else
> + node = &(*node)->rb_right;
> + }
> +
> + data = zalloc(sizeof(*data));
> + if (!data)
> + return true;
> +
> + data->addr = addr;
> + strlcpy(data->path, path, sizeof(data->path));
nit: perhaps strdup rather than having 4kb per tested_section.
Thanks,
Ian
> + rb_link_node(&data->rb_node, parent, node);
> + rb_insert_color(&data->rb_node, tested_sections);
> + return false;
> +}
> +
> +static void tested_sections__free(struct rb_root *root)
> +{
> + while (!RB_EMPTY_ROOT(root)) {
> + struct rb_node *node = rb_first(root);
> + struct tested_section *ts = rb_entry(node,
> + struct tested_section,
> + rb_node);
> +
> + rb_erase(node, root);
> + free(ts);
> + }
> +}
> +
> static size_t read_objdump_chunk(const char **line, unsigned char **buf,
> size_t *buf_len)
> {
> @@ -316,13 +370,15 @@ static void dump_buf(unsigned char *buf, size_t len)
> }
>
> static int read_object_code(u64 addr, size_t len, u8 cpumode,
> - struct thread *thread, struct state *state)
> + struct thread *thread,
> + struct rb_root *tested_sections)
> {
> struct addr_location al;
> unsigned char buf1[BUFSZ] = {0};
> unsigned char buf2[BUFSZ] = {0};
> size_t ret_len;
> u64 objdump_addr;
> + u64 skip_addr;
> const char *objdump_name;
> char decomp_name[KMOD_DECOMP_LEN];
> bool decomp = false;
> @@ -350,6 +406,18 @@ static int read_object_code(u64 addr, size_t len, u8 cpumode,
> goto out;
> }
>
> + /*
> + * Don't retest the same addresses. objdump struggles with kcore - try
> + * each map only once even if the address is different.
> + */
> + skip_addr = dso__is_kcore(dso) ? map__start(al.map) : al.addr;
> + if (tested_code_insert_or_exists(dso__long_name(dso), skip_addr,
> + tested_sections)) {
> + pr_debug("Already tested %s @ %#"PRIx64" - skipping\n",
> + dso__long_name(dso), skip_addr);
> + goto out;
> + }
> +
> pr_debug("On file address is: %#"PRIx64"\n", al.addr);
>
> if (len > BUFSZ)
> @@ -387,24 +455,6 @@ static int read_object_code(u64 addr, size_t len, u8 cpumode,
> goto out;
> }
>
> - /* objdump struggles with kcore - try each map only once */
> - if (dso__is_kcore(dso)) {
> - size_t d;
> -
> - for (d = 0; d < state->done_cnt; d++) {
> - if (state->done[d] == map__start(al.map)) {
> - pr_debug("kcore map tested already");
> - pr_debug(" - skipping\n");
> - goto out;
> - }
> - }
> - if (state->done_cnt >= ARRAY_SIZE(state->done)) {
> - pr_debug("Too many kcore maps - skipping\n");
> - goto out;
> - }
> - state->done[state->done_cnt++] = map__start(al.map);
> - }
> -
> objdump_name = dso__long_name(dso);
> if (dso__needs_decompress(dso)) {
> if (dso__decompress_kmodule_path(dso, objdump_name,
> @@ -471,9 +521,9 @@ static int read_object_code(u64 addr, size_t len, u8 cpumode,
> return err;
> }
>
> -static int process_sample_event(struct machine *machine,
> - struct evlist *evlist,
> - union perf_event *event, struct state *state)
> +static int process_sample_event(struct machine *machine, struct evlist *evlist,
> + union perf_event *event,
> + struct rb_root *tested_sections)
> {
> struct perf_sample sample;
> struct thread *thread;
> @@ -494,7 +544,8 @@ static int process_sample_event(struct machine *machine,
> goto out;
> }
>
> - ret = read_object_code(sample.ip, READLEN, sample.cpumode, thread, state);
> + ret = read_object_code(sample.ip, READLEN, sample.cpumode, thread,
> + tested_sections);
> thread__put(thread);
> out:
> perf_sample__exit(&sample);
> @@ -502,10 +553,11 @@ static int process_sample_event(struct machine *machine,
> }
>
> static int process_event(struct machine *machine, struct evlist *evlist,
> - union perf_event *event, struct state *state)
> + union perf_event *event, struct rb_root *tested_sections)
> {
> if (event->header.type == PERF_RECORD_SAMPLE)
> - return process_sample_event(machine, evlist, event, state);
> + return process_sample_event(machine, evlist, event,
> + tested_sections);
>
> if (event->header.type == PERF_RECORD_THROTTLE ||
> event->header.type == PERF_RECORD_UNTHROTTLE)
> @@ -525,7 +577,7 @@ static int process_event(struct machine *machine, struct evlist *evlist,
> }
>
> static int process_events(struct machine *machine, struct evlist *evlist,
> - struct state *state)
> + struct rb_root *tested_sections)
> {
> union perf_event *event;
> struct mmap *md;
> @@ -537,7 +589,7 @@ static int process_events(struct machine *machine, struct evlist *evlist,
> continue;
>
> while ((event = perf_mmap__read_event(&md->core)) != NULL) {
> - ret = process_event(machine, evlist, event, state);
> + ret = process_event(machine, evlist, event, tested_sections);
> perf_mmap__consume(&md->core);
> if (ret < 0)
> return ret;
> @@ -637,9 +689,7 @@ static int do_test_code_reading(bool try_kcore)
> .uses_mmap = true,
> },
> };
> - struct state state = {
> - .done_cnt = 0,
> - };
> + struct rb_root tested_sections = RB_ROOT;
> struct perf_thread_map *threads = NULL;
> struct perf_cpu_map *cpus = NULL;
> struct evlist *evlist = NULL;
> @@ -773,7 +823,7 @@ static int do_test_code_reading(bool try_kcore)
>
> evlist__disable(evlist);
>
> - ret = process_events(machine, evlist, &state);
> + ret = process_events(machine, evlist, &tested_sections);
> if (ret < 0)
> goto out_put;
>
> @@ -793,6 +843,7 @@ static int do_test_code_reading(bool try_kcore)
> perf_thread_map__put(threads);
> machine__delete(machine);
> perf_env__exit(&host_env);
> + tested_sections__free(&tested_sections);
>
> return err;
> }
>
> ---
> base-commit: a22d167ed82505f770340c3a7c257c04ba24dac9
> change-id: 20251006-james-perf-object-code-reading-9646e486d595
>
> Best regards,
> --
> James Clark <james.clark@...aro.org>
>
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