Stackcollapse perf streaming

README.md

@@ -223,3 +223,18 @@ Take a look at the demo directory for an example:
 
 palette-example-working.svg  
 palette-example-broken.svg
+
+Streaming mode
+==============
+
+`stackcollapse-perf.pl` provides a streaming mode. This mode output the
+stack sample lines in a streaming fashion. This can be used to efficiently
+subsample from a large capture:
+
+~~~sh
+perf script |
+./stackcollapse-perf.pl --stream |
+shuf -n 50000 |          # Take 50000 random stack samples
+./stackcollapse-sum.pl | # Merge identical stack samples
+./flamegraph.pl
+~~~

stackcollapse-perf.pl

@@ -88,6 +88,7 @@ sub remember_stack {
 
 my $show_inline = 0;
 my $show_context = 0;
+my $streaming = 0;        # stream the stacks without summing them
 
 my $srcline_in_input = 0; # if there are extra lines with source location (perf script -F+srcline)
 GetOptions('inline' => \$show_inline,
@@ -99,7 +100,8 @@ sub remember_stack {
            'all' => \$annotate_all,
            'tid' => \$include_tid,
            'addrs' => \$include_addrs,
-           'event-filter=s' => \$event_filter)
+           'event-filter=s' => \$event_filter,
+           'streaming'      => \$streaming)
 or die <<USAGE_END;
 USAGE: $0 [options] infile > outfile\n
 	--pid		# include PID with process names [1]
@@ -111,7 +113,8 @@ sub remember_stack {
 	--context	# adds source context to --inline
 	--srcline	# parses output of 'perf script -F+srcline' and adds source context
 	--addrs		# include raw addresses where symbols can't be found
-	--event-filter=EVENT	# event name filter\n
+	--event-filter=EVENT	# event name filter
+	--streaming	# stream the stacks without summing them\n
 [1] perf script must emit both PID and TIDs for these to work; eg, Linux < 4.1:
 	perf script -f comm,pid,tid,cpu,time,event,ip,sym,dso,trace
     for Linux >= 4.1:
@@ -233,7 +236,11 @@ sub inline {
 				unshift @stack, "";
 			}
 		}
-		remember_stack(join(";", @stack), $m_period) if @stack;
+		if ($streaming) {
+			print join(";", @stack) . " $m_period\n" if @stack;
+		} else {
+			remember_stack(join(";", @stack), $m_period) if @stack;
+		}
 		undef @stack;
 		undef $pname;
 		next;
@@ -430,6 +437,9 @@ sub inline {
 	}
 }
 
+if ($streaming) {
+	exit(0);
+}
 foreach my $k (sort { $a cmp $b } keys %collapsed) {
 	print "$k $collapsed{$k}\n";
 }

stackcollapse-sum.pl

@@ -0,0 +1,47 @@
+#!/usr/bin/perl -ws
+#
+# stackcollapse-sum  Merge identical stack samples
+#
+# Example input:
+#
+#     foo;bar 1
+#     foo;bar 1
+#
+# Output:
+#
+#     foo;bar 2
+#
+# Copyright 2022 Gabriel Corona. All rights reserved.
+#
+# CDDL HEADER START
+#
+# The contents of this file are subject to the terms of the
+# Common Development and Distribution License (the "License").
+# You may not use this file except in compliance with the License.
+#
+# You can obtain a copy of the license at docs/cddl1.txt or
+# http://opensource.org/licenses/CDDL-1.0.
+# See the License for the specific language governing permissions
+# and limitations under the License.
+#
+# When distributing Covered Code, include this CDDL HEADER in each
+# file and include the License file at docs/cddl1.txt.
+# If applicable, add the following below this CDDL HEADER, with the
+# fields enclosed by brackets "[]" replaced with your own identifying
+# information: Portions Copyright [yyyy] [name of copyright owner]
+#
+# CDDL HEADER END
+
+my %stacks;
+
+while(<>) {
+  chomp;
+  my ($stack, $value) = (/^(.*)\s+?(\d+(?:\.\d*)?)$/);
+  if ($stack) {
+    $stacks{$stack} += $value;
+  }
+}
+
+foreach my $k (sort { $a cmp $b } keys %stacks) {
+  print "$k $stacks{$k}\n";
+}