On 03/13/2014 01:30 PM, Andi Kleen wrote: > William Cohen <wco...@redhat.com> writes: > >> When experimenting with perf I wanted to have separate counts for events in >> userspace and the kernel. I used: >> >> $ perf stat -e instructions:u -e instructions:k -e cycles:u -e cycles:k -e >> cache-misses:u -e cache-misses:k make >> >> The associated output below includes the event modifiers for all the >> events, but the 3.06 and 0.37 insns per cycles look off. Shouldn't that >> instructions:u/cycles:u and instructions:k/cycles:k be the values reported >> for "insns per cycle"? > > Yes the event match code currently assumes there's only a single event > each and always uses the last. > >> It appears that the output is listing the measurements in the same >> order they are specified on the command line, but it would be nice if >> the output was clearer on the events being measured. If I am reading >> the output correctly, the L1-icache-load-misses per instruction is >> pretty poor for kernel-space. Much of the time I am looking at ratios >> of events and it would be nice if "perf stat" had a way to have it >> compute the ratios directly. Maybe a "-m, --math" option allowing >> algebraic expressions where you could do:
Hi Andi, So the missing event modifier is still a problem. The events begins passed into the perf are not going to match the names on the output. Also a script using the output perf is not going to be able to distinguish between the same event with different modifiers. > > Most people just use -x, and load the result into a spread sheet or > other script that does the compuations. At some point you usually want > to plot the data or do other more complex manipulations than your > simple facility would provide. > > You may also find this script useful > > https://github.com/andikleen/pmu-tools/blob/master/interval-normalize.py > > -Andi > Thanks for the pointer to the interval-normalize.py script. Yes, many people are probably using other more sophisticated tools such as spread sheets to analyze the data from perf. However, something like a "-m, --math" option would give a bit more insight than the basic "perf stat" without having to resort to more sophisticated tools. "perf stat" is already generating all sorts of derived numbers such as IPC, events/second, and perccent of cache misses it seems like a small step to provide some flexibility for the user to specify exactly what to compute. -Will -- To unsubscribe from this list: send the line "unsubscribe linux-perf-users" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
