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Ruby GC timing discrepancy
#!/usr/bin/env ruby
puts "Run this in another terminal:"
puts ""
puts " sudo ./trace-gc-standalone.sh #{$$}"
puts ""
puts "... wait for the 'Ready!' message, switch back here and press enter to start."
GC::Profiler.enable
$stdin.gets
GC::Profiler.clear
time_before = GC::Profiler.total_time
# Generate some GC stress...
300.times do
symbols = (1..1000).to_a.map { |i| "s#{i}".to_sym }.shuffle
10.times { symbols.sort }
end
time_after = GC::Profiler.total_time
records = GC::Profiler.raw_data
total_gc_time = time_after - time_before
mark_times = records.map { |r| r[:GC_MARK_TIME] }.compact
sweep_times = records.map { |r| r[:GC_SWEEP_TIME] }.compact
total_mark_time = mark_times.inject(:+)
total_sweep_time = sweep_times.inject(:+)
puts "Total mark time: %.1f ms" % [total_mark_time * 1000]
puts "Total sweep time: %.1f ms" % [total_sweep_time * 1000]
puts "Total GC time: %.1f ms" % [total_gc_time * 1000]
#!/bin/bash
PID=$1
cat > /tmp/dtracetmp.$$ <<EOF
#!/usr/sbin/dtrace -s
#pragma D option bufsize=16m
#pragma D option dynvarsize=16m
#pragma D option cleanrate=50Hz
BEGIN {
printf("Ready! (Go press enter on the original script.)\n");
}
ruby${PID}:::gc-mark-begin {
self->mark_begin = timestamp;
}
ruby${PID}:::gc-mark-end /self->mark_begin/ {
elapsed = timestamp - self->mark_begin;
@mark_total = sum(elapsed);
@total = sum(elapsed);
self->mark_begin = 0;
}
ruby${PID}:::gc-sweep-begin {
self->sweep_begin = timestamp;
}
ruby${PID}:::gc-sweep-end /self->sweep_begin/ {
elapsed = timestamp - self->sweep_begin;
@sweep_total = sum(elapsed);
@total = sum(elapsed);
self->sweep_begin = 0;
}
END {
normalize(@mark_total, 1000000);
normalize(@sweep_total, 1000000);
normalize(@total, 1000000);
printa("Mark total: %@d ms\n", @mark_total);
printa("Sweep total: %@d ms\n", @sweep_total);
printa("Mark + sweep total: %@d ms\n", @total)
}
EOF
dtrace -q -s /tmp/dtracetmp.$$ -p $PID
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