* Alexander Kampmann (alexander.kampm...@gmx.de) wrote: > hey, > > I would like to find out which part of my application causes most cache > misses. So I tried to add userspace events to my application. I hoped > LTTng would give me some mean of determining between which tracepoints > the most cache misses occur. > > I started a session like that: > > sudo lttng create session > sudo lttng enable-event -a -u > sudo lttng add-context -u -t perf:LLC-load-misses -t > perf:LLC-store-misses -t perf:LLC-prefetch-misses > > I get: > > Error: perf:LLC-prefetch-misses: UST invalid context > Error: perf:LLC-store-misses: UST invalid context > Error: perf:LLC-load-misses: UST invalid context > > Does this mean I can not add perf:LLC-* context to my userspace events? > Is there any way to figure out which part of my application causes cache > misses?
Currently, perf counters are only for kernel tracing (-k domain). We envision using those counters from user-space when Linux kernel support will be there. > > If I use > > sudo lttng add-context -k -t perf:LLC-load-misses -t > perf:LLC-store-misses -t perf:LLC-prefetch-misses > > instead, I don't get an error, but the babeltrace output does not > contain any cache miss counts as well. Does it contain _any_ performance counters at all ? Did you ensure that you issue add-context before you start tracing ? How many performance counters does your machine have ? Shown by dmesg, e.g.: dmesg |grep "generic reg" Thanks, Mathieu > > I would appreciate any help, > > Alex > > _______________________________________________ > lttng-dev mailing list > lttng-dev@lists.lttng.org > http://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev -- Mathieu Desnoyers Operating System Efficiency R&D Consultant EfficiOS Inc. http://www.efficios.com _______________________________________________ lttng-dev mailing list lttng-dev@lists.lttng.org http://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev
