Hi Andi, On Fri, Sep 11, 2020 at 1:05 AM Andi Kleen <a...@firstfloor.org> wrote: > > On Tue, Sep 08, 2020 at 01:42:24PM +0900, Namhyung Kim wrote: > > When we profile cgroup events with perf stat, it's very annoying to > > specify events and cgroups on the command line as it requires the > > mapping between events and cgroups. (Note that perf record can use > > cgroup sampling but it's not usable for perf stat). > > The problem is real, but I don't really like your solution. > The option is ugly. Should rather be solved with some suitable > syntax in the expression parser to express: apply to all, > instead of adding adhoc options like this.
Yeah, I'd admit that I'm terrible at naming. :) I'm open to any suggestions as I'm also bad at making new syntax.. But as Ian said, my approach takes care of the common case without dealing with controversial syntax changes. > > There are some additional problems that really need to be eventually > solved too: > > - If you use the old syntax and some cgroups are not covered you don't > get any warning. At least that should be fixed too. I don't follow. Do you mean like when -G option and --multiply-cgroup option is used at the same time? Or when -G option doesn't match to -e option? > > - And of course if everything works it is still very slow for the kernel > because there are so many perf events to handle. Long term we probably > need some more flexible way to just specify for given perf events which set of > cgroups they should apply, so that sharing and low overhead monitoring > of many cgroups is possible I hate to say it, but maybe some eBPF filter > is the solution here. Yes, I'm also interested in improving that too. Thanks Namhyung