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SubjectRe: [PATCH 4/6] tracing, page-allocator: Add a postprocessing script for page-allocator-related ftrace events
On Fri, Aug 07, 2009 at 10:00:18AM +0200, Ingo Molnar wrote:
> * Mel Gorman <> wrote:
> > This patch adds a simple post-processing script for the
> > page-allocator-related trace events. It can be used to give an
> > indication of who the most allocator-intensive processes are and
> > how often the zone lock was taken during the tracing period.
> > Example output looks like
> Note, this script hard-codes certain aspects of the output format:

Yes, I noted that to some extent in the header with "The accuracy of the
parser may vary considerably" knowing that significant changes in the output
format would bust the script.

> +my $regex_traceevent =
> +'\s*([a-zA-Z0-9-]*)\s*(\[[0-9]*\])\s*([0-9.]*):\s*([a-zA-Z_]*):\s*(.*)';
> +my $regex_fragdetails = 'page=([0-9a-f]*) pfn=([0-9]*) alloc_order=([0-9]*)
> +fallback_order=([0-9]*) pageblock_order=([0-9]*) alloc_migratetype=([0-9]*)
> +fallback_migratetype=([0-9]*) fragmenting=([0-9]) change_ownership=([0-9])';
> +my $regex_statname = '[-0-9]*\s\((.*)\).*';
> +my $regex_statppid = '[-0-9]*\s\(.*\)\s[A-Za-z]\s([0-9]*).*';
> the proper appproach is to parse /debug/tracing/events/mm/*/format.
> That is why we emit a format string - to detach tools and reduce the
> semi-ABI effect.

Building a regularly expression is a tad messy but I can certainly do a
better job than currently. The information on every tracepoint seems
static so it doesn't need to be discovered but the trace format of the
details needs to be verified. I did the following and it should

o Ignore unrecognised fields in the middle of the format string
o Exit if expected fields do not exist
o It's not pasted, but it'll warn if the regex fails to match

Downsides include that I now hardcode the mount point of debugfs.

Basically, this can still break but it's more robust than it was.

# Defaults for dynamically discovered regex's
my $regex_fragdetails_default = 'page=([0-9a-f]*) pfn=([0-9]*) alloc_order=([-0-9]*) fallback_order=([-0-9]*) pageblock_order=([-0-9]*) alloc_migratetype=([-0-9]*) fallback_migratetype=([-0-9]*) fragmenting=([-0-9]) change_ownership=([-0-9])';

# Dyanically discovered regex
my $regex_fragdetails;

# Static regex used. Specified like this for readability and for use with /o
# (process_pid) (cpus ) ( time ) (tpoint ) (details)
my $regex_traceevent = '\s*([a-zA-Z0-9-]*)\s*(\[[0-9]*\])\s*([0-9.]*):\s*([a-zA-Z_]*):\s*(.*)';
my $regex_statname = '[-0-9]*\s\((.*)\).*';
my $regex_statppid = '[-0-9]*\s\(.*\)\s[A-Za-z]\s([0-9]*).*';

sub generate_traceevent_regex {
my $event = shift;
my $default = shift;
my @fields = @_;
my $regex;

# Read the event format or use the default
if (!open (FORMAT, "/sys/kernel/debug/tracing/events/$event/format")) {
$regex = $default;
} else {
my $line;
while (!eof(FORMAT)) {
$line = <FORMAT>;
if ($line =~ /^print fmt:\s"(.*)",.*/) {
$regex = $1;
$regex =~ s/%p/\([0-9a-f]*\)/g;
$regex =~ s/%d/\([-0-9]*\)/g;
$regex =~ s/%lu/\([0-9]*\)/g;

# Verify fields are in the right order
my $tuple;
foreach $tuple (split /\s/, $regex) {
my ($key, $value) = split(/=/, $tuple);
my $expected = shift;
if ($key ne $expected) {
print("WARNING: Format not as expected '$key' != '$expected'");
$regex =~ s/$key=\((.*)\)/$key=$1/;
if (defined $_) {
die("Fewer fields than expected in format");

return $regex;
$regex_fragdetails = generate_traceevent_regex("kmem/mm_page_alloc_extfrag",
"page", "pfn",
"alloc_order", "fallback_order", "pageblock_order",
"alloc_migratetype", "fallback_migratetype",
"fragmenting", "change_ownership");

Mel Gorman
Part-time Phd Student Linux Technology Center
University of Limerick IBM Dublin Software Lab

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