This patch allows passing perf's own PID to '--filter' by using
'@PERFPID'. This should be useful when system-widely capturing
tracepoints events.
Before this patch, when doing something like:
# perf record -a -e syscalls:sys_enter_write <cmd>
One could easily get result like this:
# /tmp/perf report --stdio
...
# Overhead Command Shared Object Symbol
# ........ ....... .................. ....................
#
99.99% perf libpthread-2.18.so [.] __write_nocancel
0.01% ls libc-2.18.so [.] write
0.01% sshd libc-2.18.so [.] write
...
Where most events are generated by perf itself.
A shell trick can be done to filter perf itself out:
# cat << EOF > ./tmp
> #!/bin/sh
> exec perf record -e ... --filter="common_pid != \$\$" -a sleep 10
> EOF
# chmod a+x ./tmp
# ./tmp
However, doing so is user unfriendly.
This patch introduces '@PERFPID' placeholder to '--filter' options. Now
user is allowed to the above work with:
# perf record -e ... --filter="common_pid != @PERFPID' sleep 10
Signed-off-by: Wang Nan <wangn...@huawei.com>
---
tools/perf/Documentation/perf-record.txt | 1 +
tools/perf/util/parse-events.c | 96 ++++++++++++++++++++++++++++++++
2 files changed, 97 insertions(+)
diff --git a/tools/perf/Documentation/perf-record.txt
b/tools/perf/Documentation/perf-record.txt
index 9b9d9d0..c2902d2 100644
--- a/tools/perf/Documentation/perf-record.txt
+++ b/tools/perf/Documentation/perf-record.txt
@@ -62,6 +62,7 @@ OPTIONS
--filter=<filter>::
Event filter.
+ String '@PERFPID' is allowed to be used to represent pid of 'perf'
itself.
-a::
--all-cpus::
diff --git a/tools/perf/util/parse-events.c b/tools/perf/util/parse-events.c
index aaee24c..2d62957 100644
--- a/tools/perf/util/parse-events.c
+++ b/tools/perf/util/parse-events.c
@@ -1175,6 +1175,101 @@ int parse_events_option(const struct option *opt, const
char *str,
return ret;
}
+#ifndef PAGE_SIZE
+# define PAGE_SIZE 4096
+#endif
+static int
+postproc_filter_append_token(const char *key, char *new_filter,
+ ssize_t *pspace)
+{
+ if (strcmp(key, "PERFPID") == 0) {
+ char pid_buf[32];
+ pid_t self_pid = getpid();
+
+ snprintf(pid_buf, 32, "%d", self_pid);
+ strncat(new_filter, pid_buf, *pspace);
+ *pspace -= strlen(pid_buf);
+ if (*pspace < 0)
+ return -1;
+ return 0;
+ }
+
+ return -1;
+}
+
+static void postproc_filter(struct perf_evsel *evsel)
+{
+ char *at = NULL, *sep = NULL, *old_filter, *new_filter;
+ ssize_t space;
+
+ if (!evsel->filter)
+ return;
+
+ old_filter = evsel->filter;
+ at = strchr(old_filter, '@');
+ if (!at)
+ return;
+
+ /*
+ * See perf_event_set_filter(). Length of a valid filter is
+ * limited by PAGE_SIZE.
+ */
+ new_filter = malloc(PAGE_SIZE);
+ if (!new_filter) {
+ fprintf(stderr, "No enough memory for post proc filter '%s'\n",
+ old_filter);
+ return;
+ }
+ *new_filter = '\0';
+ space = PAGE_SIZE - 1;
+
+ while (1) {
+ if (at)
+ *at = '\0';
+ strncat(new_filter, old_filter, space);
+ space -= strlen(old_filter);
+ if (space < 0)
+ goto errout;
+ if (!at)
+ break;
+ *at = '@';
+
+ sep = strchr(at + 1, ' ');
+ if (sep)
+ *sep = '\0';
+
+ if (postproc_filter_append_token(at + 1, new_filter, &space))
+ goto errout;
+
+ if (!sep)
+ break;
+ *sep = ' ';
+
+ old_filter = sep;
+ at = strchr(old_filter, '@');
+ }
+
+ free(evsel->filter);
+ /*
+ * It is safe to use new_filter directly. However, try to
+ * release some memory by strdup() a smaller string and free
+ * new_filter, which takes a full page.
+ */
+ evsel->filter = strdup(new_filter);
+ if (!evsel->filter)
+ evsel->filter = new_filter;
+ else
+ free(new_filter);
+ return;
+errout:
+ if (at)
+ *at = '@';
+ if (sep)
+ *sep = ' ';
+ fprintf(stderr, "Can't post proc filter '%s'\n", evsel->filter);
+ free(new_filter);
+}
+
int parse_filter(const struct option *opt, const char *str,
int unset __maybe_unused)
{
@@ -1196,6 +1291,7 @@ int parse_filter(const struct option *opt, const char
*str,
return -1;
}
+ postproc_filter(last);
return 0;
}
--
1.8.3.4
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
