On Fri, Sep 01, 2017 at 06:57:59PM +0200, Jiri Olsa wrote: > On Thu, Aug 31, 2017 at 12:40:26PM -0700, Andi Kleen wrote: > > From: Andi Kleen <[email protected]> > > > > Setting up groups can be complicated due to the > > complicated scheduling restrictions of different PMUs. > > User tools usually don't understand all these restrictions. > > Still in many cases it is useful to set up groups and > > they work most of the time. However if the group > > is set up wrong some members will not reported any values > > because they never get scheduled. > > > > Add a concept of a 'weak group': try to set up a group, > > but if it's not schedulable fallback to not using > > a group. That gives us the best of both worlds: > > groups if they work, but still a usable fallback if they don't. > > > > In theory it would be possible to have more complex fallback > > strategies (e.g. try to split the group in half), but > > the simple fallback of not using a group seems to work for now. > > > > So far the weak group is only implemented for perf stat, > > not for record. > > > > Here's an unschedulable group (on IvyBridge with SMT on) > > > > % perf stat -e > > '{branches,branch-misses,l1d.replacement,l2_lines_in.all,l2_rqsts.all_code_rd}' > > -a sleep 1 > > > > 73,806,067 branches > > 4,848,144 branch-misses # 6.57% of all branches > > 14,754,458 l1d.replacement > > 24,905,558 l2_lines_in.all > > <not supported> l2_rqsts.all_code_rd <------- will never > > report anything > > > > With the weak group: > > > > % perf stat -e > > '{branches,branch-misses,l1d.replacement,l2_lines_in.all,l2_rqsts.all_code_rd}:W' > > -a sleep 1 > > > > 125,366,055 branches > > (80.02%) > > 9,208,402 branch-misses # 7.35% of all > > branches (80.01%) > > 24,560,249 l1d.replacement > > (80.00%) > > 43,174,971 l2_lines_in.all > > (80.05%) > > 31,891,457 l2_rqsts.all_code_rd > > (79.92%) > > > > The extra event scheduled with some extra multiplexing > > > > v2: Move fallback code to separate function. > > Add comment on for_each_group_member > > Adjust to new perf_evsel__close interface > > v3: > > Fix debug print out. > > Signed-off-by: Andi Kleen <[email protected]> > > Acked-by: Jiri Olsa <[email protected]>
just realized we support this in stat only and the doc indicates it's global.. maybe the perf-list.txt line could have the '(perf stat only)' suffix ;-) jirka
