[PATCH 0/2] perf scripts: Fix rwtop script

[PATCH 0/2] perf scripts: Fix rwtop script

[Jiri Olsa]

hi,
sending patches for rwtop race issue caused by rwtop script
triggering SIGALRM and underneath pipe reading layer reporting
error when interrupted.

It's discussed in here:
https://lkml.org/lkml/2012/9/14/381

thanks,
jirka

Cc: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Andrew Jones <drjones@redhat.com>
Cc: David Ahern <dsahern@gmail.com>
---
Jiri Olsa (2):
      perf scripts: Fix SIGALRM and pipe read race for rwtop
      perf scripts: Fix rwtop record script

 tools/perf/scripts/perl/bin/rwtop-record | 2 +-
 tools/perf/scripts/perl/rwtop.pl         | 6 +++++-
 2 files changed, 6 insertions(+), 2 deletions(-)

[PATCH 1/2] perf scripts: Fix SIGALRM and pipe read race for rwtop

[Jiri Olsa]

Fixing rwtop script race. The issue is caused by rwtop
script triggering SIGALRM and underneath pipe reading
layer reporting error when interrupted.

Fixing this by setting SA_RESTART for rwtop SIGALRM handler,
which avoids interruption of the pipe reading layer.

The discussion for this issue & fix is here:
https://lkml.org/lkml/2012/9/18/123

Original-patch-by: Andrew Jones <drjones@redhat.com>
Signed-off-by: Jiri Olsa <jolsa@redhat.com>
Cc: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Andrew Jones <drjones@redhat.com>
Cc: David Ahern <dsahern@gmail.com>
---
 tools/perf/scripts/perl/rwtop.pl | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/tools/perf/scripts/perl/rwtop.pl b/tools/perf/scripts/perl/rwtop.pl
index 4bb3ecd..8b20787 100644
--- a/tools/perf/scripts/perl/rwtop.pl
+++ b/tools/perf/scripts/perl/rwtop.pl
@@ -17,6 +17,7 @@ use lib "$ENV{'PERF_EXEC_PATH'}/scripts/perl/Perf-Trace-Util/lib";
 use lib "./Perf-Trace-Util/lib";
 use Perf::Trace::Core;
 use Perf::Trace::Util;
+use POSIX qw/SIGALRM SA_RESTART/;
 
 my $default_interval = 3;
 my $nlines = 20;
@@ -90,7 +91,10 @@ sub syscalls::sys_enter_write
 
 sub trace_begin
 {
-    $SIG{ALRM} = \&set_print_pending;
+    my $sa = POSIX::SigAction->new(\&set_print_pending);
+    $sa->flags(SA_RESTART);
+    $sa->safe(1);
+    POSIX::sigaction(SIGALRM, $sa) or die "Can't set SIGALRM handler: $!\n";
     alarm 1;
 }
 
-- 
1.7.11.7

[PATCH 2/2] perf scripts: Fix rwtop record script

[Jiri Olsa]

Adding -D option into the rwtop record command line, to get
immediate response when there's event in the buffer.

Otherwise we need to wait till half of the buffer is filled,
which is the default wattermark if it's not set.

Suggested-by: Andrew Jones <drjones@redhat.com>
Signed-off-by: Jiri Olsa <jolsa@redhat.com>
Cc: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Andrew Jones <drjones@redhat.com>
Cc: David Ahern <dsahern@gmail.com>
---
 tools/perf/scripts/perl/bin/rwtop-record | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/perf/scripts/perl/bin/rwtop-record b/tools/perf/scripts/perl/bin/rwtop-record
index 7cb9db2..e4ec090 100644
--- a/tools/perf/scripts/perl/bin/rwtop-record
+++ b/tools/perf/scripts/perl/bin/rwtop-record
@@ -1,2 +1,2 @@
 #!/bin/bash
-perf record -e syscalls:sys_enter_read -e syscalls:sys_exit_read -e syscalls:sys_enter_write -e syscalls:sys_exit_write $@
+perf record -e syscalls:sys_enter_read -e syscalls:sys_exit_read -e syscalls:sys_enter_write -e syscalls:sys_exit_write -D $@
-- 
1.7.11.7

Re: [PATCH 2/2] perf scripts: Fix rwtop record script

[David Ahern]

On 2/5/13 9:05 AM, Jiri Olsa wrote:
> Adding -D option into the rwtop record command line, to get
> immediate response when there's event in the buffer.

Seems like this will dramatically increase CPU usage of perf-record as 
well as increase the overhead of each event with a process wakeup. How 
about a poll option on perf-record to have it wake up at a given rate 
instead?

David

Re: [PATCH 2/2] perf scripts: Fix rwtop record script

[Jiri Olsa]

On Tue, Feb 05, 2013 at 09:15:20AM -0700, David Ahern wrote:
> On 2/5/13 9:05 AM, Jiri Olsa wrote:
> >Adding -D option into the rwtop record command line, to get
> >immediate response when there's event in the buffer.
> 
> Seems like this will dramatically increase CPU usage of perf-record
> as well as increase the overhead of each event with a process
> wakeup. How about a poll option on perf-record to have it wake up at
> a given rate instead?

right, I'll check

thanks,
jirka

[tip:perf/core] perf perl scripts: Fix SIGALRM and pipe read race for rwtop

[tip-bot for Jiri Olsa]

Commit-ID:  b22e79395c0fe4c86dd35745a929366034386ccc
Gitweb:     http://git.kernel.org/tip/b22e79395c0fe4c86dd35745a929366034386ccc
Author:     Jiri Olsa <jolsa@redhat.com>
AuthorDate: Tue, 5 Feb 2013 17:05:50 +0100
Committer:  Arnaldo Carvalho de Melo <acme@redhat.com>
CommitDate: Wed, 6 Feb 2013 18:09:27 -0300

perf perl scripts: Fix SIGALRM and pipe read race for rwtop

Fixing rwtop script race. The issue is caused by rwtop script triggering
SIGALRM and underneath pipe reading layer reporting error when
interrupted.

Fixing this by setting SA_RESTART for rwtop SIGALRM handler, which
avoids interruption of the pipe reading layer.

The discussion for this issue & fix is here:
https://lkml.org/lkml/2012/9/18/123

Signed-off-by: Jiri Olsa <jolsa@redhat.com>
Original-patch-by: Andrew Jones <drjones@redhat.com>
Cc: Andrew Jones <drjones@redhat.com>
Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1360080351-3246-2-git-send-email-jolsa@redhat.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
 tools/perf/scripts/perl/rwtop.pl | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/tools/perf/scripts/perl/rwtop.pl b/tools/perf/scripts/perl/rwtop.pl
index 4bb3ecd..8b20787 100644
--- a/tools/perf/scripts/perl/rwtop.pl
+++ b/tools/perf/scripts/perl/rwtop.pl
@@ -17,6 +17,7 @@ use lib "$ENV{'PERF_EXEC_PATH'}/scripts/perl/Perf-Trace-Util/lib";
 use lib "./Perf-Trace-Util/lib";
 use Perf::Trace::Core;
 use Perf::Trace::Util;
+use POSIX qw/SIGALRM SA_RESTART/;
 
 my $default_interval = 3;
 my $nlines = 20;
@@ -90,7 +91,10 @@ sub syscalls::sys_enter_write
 
 sub trace_begin
 {
-    $SIG{ALRM} = \&set_print_pending;
+    my $sa = POSIX::SigAction->new(\&set_print_pending);
+    $sa->flags(SA_RESTART);
+    $sa->safe(1);
+    POSIX::sigaction(SIGALRM, $sa) or die "Can't set SIGALRM handler: $!\n";
     alarm 1;
 }