Messages in this thread | | | Date | Fri, 7 Aug 2009 15:16:50 +0100 | From | Mel Gorman <> | Subject | Re: [PATCH 4/6] tracing, page-allocator: Add a postprocessing script for page-allocator-related ftrace events |
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On Fri, Aug 07, 2009 at 10:00:18AM +0200, Ingo Molnar wrote: > > * Mel Gorman <mel@csn.ul.ie> 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", $regex_fragdetails_default, "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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