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Subject[tip:perf/live] perf record: Introduce special handling for pipe output
Commit-ID:  529870e37473a9fc609078f03cc5b4148cf06a87
Gitweb: http://git.kernel.org/tip/529870e37473a9fc609078f03cc5b4148cf06a87
Author: Tom Zanussi <tzanussi@gmail.com>
AuthorDate: Thu, 1 Apr 2010 23:59:16 -0500
Committer: Ingo Molnar <mingo@elte.hu>
CommitDate: Wed, 14 Apr 2010 11:56:06 +0200

perf record: Introduce special handling for pipe output

Adds special treatment for stdout - if the user specifies '-o -'
to perf record, the intent is that the event stream be written
to stdout rather than to a disk file.

Also, redirect stdout of forked child to stderr - in pipe mode,
stdout of the forked child interferes with the stdout perf
stream, so redirect it to stderr where it can still be seen but
won't be mixed in with the perf output.

Signed-off-by: Tom Zanussi <tzanussi@gmail.com>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Cc: fweisbec@gmail.com
Cc: rostedt@goodmis.org
Cc: k-keiichi@bx.jp.nec.com
Cc: acme@ghostprotocols.net
LKML-Reference: <1270184365-8281-3-git-send-email-tzanussi@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
---
tools/perf/builtin-record.c | 18 +++++++++++++++---
1 files changed, 15 insertions(+), 3 deletions(-)

diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
index d060fc5..d4464f7 100644
--- a/tools/perf/builtin-record.c
+++ b/tools/perf/builtin-record.c
@@ -35,6 +35,7 @@ static unsigned int page_size;
static unsigned int mmap_pages = 128;
static int freq = 1000;
static int output;
+static int pipe_output = 0;
static const char *output_name = "perf.data";
static int group = 0;
static unsigned int realtime_prio = 0;
@@ -449,7 +450,9 @@ static int __cmd_record(int argc, const char **argv)
exit(-1);
}

- if (!stat(output_name, &st) && st.st_size) {
+ if (!strcmp(output_name, "-"))
+ pipe_output = 1;
+ else if (!stat(output_name, &st) && st.st_size) {
if (!force) {
if (!append_file) {
pr_err("Error, output file %s exists, use -A "
@@ -474,7 +477,10 @@ static int __cmd_record(int argc, const char **argv)
else
flags |= O_TRUNC;

- output = open(output_name, flags, S_IRUSR|S_IWUSR);
+ if (pipe_output)
+ output = STDOUT_FILENO;
+ else
+ output = open(output_name, flags, S_IRUSR | S_IWUSR);
if (output < 0) {
perror("failed to create output file");
exit(-1);
@@ -513,6 +519,8 @@ static int __cmd_record(int argc, const char **argv)
}

if (!child_pid) {
+ if (pipe_output)
+ dup2(2, 1);
close(child_ready_pipe[0]);
close(go_pipe[1]);
fcntl(go_pipe[0], F_SETFD, FD_CLOEXEC);
@@ -564,7 +572,11 @@ static int __cmd_record(int argc, const char **argv)
open_counters(cpumap[i]);
}

- if (file_new) {
+ if (pipe_output) {
+ err = perf_header__write_pipe(output);
+ if (err < 0)
+ return err;
+ } else if (file_new) {
err = perf_header__write(&session->header, output, false);
if (err < 0)
return err;

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