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Message-ID: <20240703223035.2024586-4-namhyung@kernel.org>
Date: Wed, 3 Jul 2024 15:30:30 -0700
From: Namhyung Kim <namhyung@...nel.org>
To: Arnaldo Carvalho de Melo <acme@...nel.org>,
Ian Rogers <irogers@...gle.com>,
Kan Liang <kan.liang@...ux.intel.com>
Cc: Jiri Olsa <jolsa@...nel.org>,
Adrian Hunter <adrian.hunter@...el.com>,
Peter Zijlstra <peterz@...radead.org>,
Ingo Molnar <mingo@...nel.org>,
LKML <linux-kernel@...r.kernel.org>,
linux-perf-users@...r.kernel.org,
KP Singh <kpsingh@...nel.org>,
Song Liu <song@...nel.org>,
bpf@...r.kernel.org,
Stephane Eranian <eranian@...gle.com>
Subject: [PATCH v3 3/8] perf bpf-filter: Split per-task filter use case
If the target is a list of tasks, it can use a shared hash map for
filter expressions. The key of the filter map is an integer index like
in an array. A separate pid_hash map is added to get the index for the
filter map using the tgid.
For system-wide mode including per-cpu or per-user targets are handled
by the single entry map like before.
Signed-off-by: Namhyung Kim <namhyung@...nel.org>
---
tools/perf/util/bpf-filter.c | 186 +++++++++++++++----
tools/perf/util/bpf_skel/sample-filter.h | 1 +
tools/perf/util/bpf_skel/sample_filter.bpf.c | 21 +++
3 files changed, 168 insertions(+), 40 deletions(-)
diff --git a/tools/perf/util/bpf-filter.c b/tools/perf/util/bpf-filter.c
index 0b2eca56aa10..5ec0e0955ec4 100644
--- a/tools/perf/util/bpf-filter.c
+++ b/tools/perf/util/bpf-filter.c
@@ -3,10 +3,13 @@
#include <bpf/bpf.h>
#include <linux/err.h>
+#include <api/fs/fs.h>
#include <internal/xyarray.h>
+#include <perf/threadmap.h>
#include "util/debug.h"
#include "util/evsel.h"
+#include "util/target.h"
#include "util/bpf-filter.h"
#include <util/bpf-filter-flex.h>
@@ -91,38 +94,17 @@ static int check_sample_flags(struct evsel *evsel, struct perf_bpf_filter_expr *
return -1;
}
-int perf_bpf_filter__prepare(struct evsel *evsel, struct target *target __maybe_unused)
+static int get_filter_entries(struct evsel *evsel, struct perf_bpf_filter_entry *entry)
{
- int i, x, y, fd, ret;
- struct sample_filter_bpf *skel;
- struct bpf_program *prog;
- struct bpf_link *link;
+ int i = 0;
struct perf_bpf_filter_expr *expr;
- struct perf_bpf_filter_entry *entry;
-
- entry = calloc(MAX_FILTERS, sizeof(*entry));
- if (entry == NULL)
- return -1;
-
- skel = sample_filter_bpf__open_and_load();
- if (!skel) {
- pr_err("Failed to load perf sample-filter BPF skeleton\n");
- ret = -EPERM;
- goto err;
- }
- i = 0;
- fd = bpf_map__fd(skel->maps.filters);
list_for_each_entry(expr, &evsel->bpf_filters, list) {
- if (check_sample_flags(evsel, expr) < 0) {
- ret = -EINVAL;
- goto err;
- }
+ if (check_sample_flags(evsel, expr) < 0)
+ return -EINVAL;
- if (i == MAX_FILTERS) {
- ret = -E2BIG;
- goto err;
- }
+ if (i == MAX_FILTERS)
+ return -E2BIG;
entry[i].op = expr->op;
entry[i].part = expr->part;
@@ -134,10 +116,8 @@ int perf_bpf_filter__prepare(struct evsel *evsel, struct target *target __maybe_
struct perf_bpf_filter_expr *group;
list_for_each_entry(group, &expr->groups, list) {
- if (i == MAX_FILTERS) {
- ret = -E2BIG;
- goto err;
- }
+ if (i == MAX_FILTERS)
+ return -E2BIG;
entry[i].op = group->op;
entry[i].part = group->part;
@@ -146,10 +126,8 @@ int perf_bpf_filter__prepare(struct evsel *evsel, struct target *target __maybe_
i++;
}
- if (i == MAX_FILTERS) {
- ret = -E2BIG;
- goto err;
- }
+ if (i == MAX_FILTERS)
+ return -E2BIG;
entry[i].op = PBF_OP_GROUP_END;
i++;
@@ -161,15 +139,143 @@ int perf_bpf_filter__prepare(struct evsel *evsel, struct target *target __maybe_
entry[i].op = PBF_OP_DONE;
i++;
}
+ return 0;
+}
+
+static int convert_to_tgid(int tid)
+{
+ char path[128];
+ char *buf, *p, *q;
+ int tgid;
+ size_t len;
+
+ scnprintf(path, sizeof(path), "%d/status", tid);
+ if (procfs__read_str(path, &buf, &len) < 0)
+ return -1;
- /* The filters map has only one entry for now */
- i = 0;
- if (bpf_map_update_elem(fd, &i, entry, BPF_ANY) < 0) {
- ret = -errno;
- pr_err("Failed to update the filter map\n");
+ p = strstr(buf, "Tgid:");
+ if (p == NULL) {
+ free(buf);
+ return -1;
+ }
+
+ tgid = strtol(p + 6, &q, 0);
+ free(buf);
+ if (*q != '\n')
+ return -1;
+
+ return tgid;
+}
+
+static int update_pid_hash(struct sample_filter_bpf *skel, struct evsel *evsel,
+ struct perf_bpf_filter_entry *entry)
+{
+ int filter_idx;
+ int nr, last;
+ int fd = bpf_map__fd(skel->maps.filters);
+ struct perf_thread_map *threads;
+
+ /* Find the first available entry in the filters map */
+ for (filter_idx = 0; filter_idx < MAX_FILTERS; filter_idx++) {
+ if (bpf_map_update_elem(fd, &filter_idx, entry, BPF_NOEXIST) == 0)
+ break;
+ }
+
+ if (filter_idx == MAX_FILTERS) {
+ pr_err("Too many users for the filter map\n");
+ return -EBUSY;
+ }
+
+ threads = perf_evsel__threads(&evsel->core);
+ if (threads == NULL) {
+ pr_err("Cannot get the thread list of the event\n");
+ return -EINVAL;
+ }
+
+ /* save the index to a hash map */
+ fd = bpf_map__fd(skel->maps.pid_hash);
+
+ last = -1;
+ nr = perf_thread_map__nr(threads);
+ for (int i = 0; i < nr; i++) {
+ int pid = perf_thread_map__pid(threads, i);
+ int tgid;
+
+ /* it actually needs tgid, let's get tgid from /proc. */
+ tgid = convert_to_tgid(pid);
+ if (tgid < 0) {
+ /* the thread may be dead, ignore. */
+ continue;
+ }
+
+ if (tgid == last)
+ continue;
+ last = tgid;
+
+ if (bpf_map_update_elem(fd, &tgid, &filter_idx, BPF_ANY) < 0) {
+ pr_err("Failed to update the pid hash\n");
+ return -errno;
+ }
+ pr_debug("pid hash: %d -> %d\n", tgid, filter_idx);
+ }
+ return 0;
+}
+
+int perf_bpf_filter__prepare(struct evsel *evsel, struct target *target)
+{
+ int i, x, y, fd, ret;
+ struct sample_filter_bpf *skel = NULL;
+ struct bpf_program *prog;
+ struct bpf_link *link;
+ struct perf_bpf_filter_entry *entry;
+ bool needs_pid_hash = !target__has_cpu(target) && !target->uid_str;
+
+ entry = calloc(MAX_FILTERS, sizeof(*entry));
+ if (entry == NULL)
+ return -1;
+
+ ret = get_filter_entries(evsel, entry);
+ if (ret < 0) {
+ pr_err("Failed to process filter entries\n");
+ goto err;
+ }
+
+ skel = sample_filter_bpf__open();
+ if (!skel) {
+ pr_err("Failed to open perf sample-filter BPF skeleton\n");
+ ret = -EPERM;
goto err;
}
+ if (needs_pid_hash) {
+ bpf_map__set_max_entries(skel->maps.filters, MAX_FILTERS);
+ bpf_map__set_max_entries(skel->maps.pid_hash, MAX_PIDS);
+ skel->rodata->use_pid_hash = 1;
+ }
+
+ if (sample_filter_bpf__load(skel) < 0) {
+ pr_err("Failed to load perf sample-filter BPF skeleton\n");
+ ret = -EPERM;
+ goto err;
+ }
+
+ if (needs_pid_hash) {
+ /* The filters map is shared among other processes */
+ ret = update_pid_hash(skel, evsel, entry);
+ if (ret < 0)
+ goto err;
+ } else {
+ i = 0;
+ fd = bpf_map__fd(skel->maps.filters);
+
+ /* The filters map has only one entry in this case */
+ if (bpf_map_update_elem(fd, &i, entry, BPF_ANY) < 0) {
+ ret = -errno;
+ pr_err("Failed to update the filter map\n");
+ goto err;
+ }
+ }
+
prog = skel->progs.perf_sample_filter;
for (x = 0; x < xyarray__max_x(evsel->core.fd); x++) {
for (y = 0; y < xyarray__max_y(evsel->core.fd); y++) {
diff --git a/tools/perf/util/bpf_skel/sample-filter.h b/tools/perf/util/bpf_skel/sample-filter.h
index bb6a1b91f1df..e666bfd5fbdd 100644
--- a/tools/perf/util/bpf_skel/sample-filter.h
+++ b/tools/perf/util/bpf_skel/sample-filter.h
@@ -2,6 +2,7 @@
#define PERF_UTIL_BPF_SKEL_SAMPLE_FILTER_H
#define MAX_FILTERS 64
+#define MAX_PIDS (16 * 1024)
/* supported filter operations */
enum perf_bpf_filter_op {
diff --git a/tools/perf/util/bpf_skel/sample_filter.bpf.c b/tools/perf/util/bpf_skel/sample_filter.bpf.c
index 0d56e52b922c..c5273f06fa45 100644
--- a/tools/perf/util/bpf_skel/sample_filter.bpf.c
+++ b/tools/perf/util/bpf_skel/sample_filter.bpf.c
@@ -15,7 +15,16 @@ struct filters {
__uint(max_entries, 1);
} filters SEC(".maps");
+/* tgid to filter index */
+struct pid_hash {
+ __uint(type, BPF_MAP_TYPE_HASH);
+ __type(key, int);
+ __type(value, int);
+ __uint(max_entries, 1);
+} pid_hash SEC(".maps");
+
int dropped;
+volatile const int use_pid_hash;
void *bpf_cast_to_kern_ctx(void *) __ksym;
@@ -184,6 +193,18 @@ int perf_sample_filter(void *ctx)
kctx = bpf_cast_to_kern_ctx(ctx);
k = 0;
+
+ if (use_pid_hash) {
+ int tgid = bpf_get_current_pid_tgid() >> 32;
+ int *idx;
+
+ idx = bpf_map_lookup_elem(&pid_hash, &tgid);
+ if (idx)
+ k = *idx;
+ else
+ goto drop;
+ }
+
entry = bpf_map_lookup_elem(&filters, &k);
if (entry == NULL)
goto drop;
--
2.45.2.803.g4e1b14247a-goog
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