Messages in this thread | | | Date | Wed, 22 Sep 2010 09:53:54 +0530 | From | Balbir Singh <> | Subject | Re: [RFC PATCH 0/2] perf_events: add support for per-cpu per-cgroup monitoring (v3) |
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* Peter Zijlstra <peterz@infradead.org> [2010-09-21 11:38:19]:
> On Thu, 2010-09-09 at 15:05 +0200, Stephane Eranian wrote: > > The cgroup to monitor is designated by passing a file descriptor opened > > on a new per-cgroup file in the cgroup filesystem (perf_event.perf). The > > option must be activated by setting perf_event_attr.cgroup=1 and passing > > a valid file descriptor in perf_event_attr.cgroup_fd. Those are the only > > two ABI extensions. > > > +++ b/include/linux/perf_event.h > > @@ -215,8 +215,9 @@ struct perf_event_attr { > > */ > > precise_ip : 2, /* skid constraint */ > > mmap_data : 1, /* non-exec mmap data */ > > + cgroup : 1, /* cgroup aggregation */ > > > > - __reserved_1 : 46; > > + __reserved_1 : 45; > > > > union { > > __u32 wakeup_events; /* wakeup every n events */ > > @@ -226,6 +227,8 @@ struct perf_event_attr { > > __u32 bp_type; > > __u64 bp_addr; > > __u64 bp_len; > > + > > + int cgroup_fd; > > }; > > > > /* > > I'm not sure I like this much.. so we attach to {pid,cpu}, for nodes we > can use cpu_to_node(cpu), which would suggest to use > cgroup_of_task(pid), except that a task can be part of multiple cgroups, > so its not unique.
Yes, a task can belong to multiple subsystems, hence multiple cgroups. Ideally we'd want to use pid + subsystem
> > One thing we could do is pass this cgroup identifier in the pid field > and use PERF_FLAG_CGROUP or something. Currently the syscall signature > uses pid_t, but I think we can safely change that to int.
Or union it and overload the field to contain either pid_t or fd of the cgroup
> > You create a special new file in the cgroup stuff, I'm not sure about > that either, but its not something I feel too strongly about, why > wouldn't a fd of any file or even directory of that cgroup work? Do the > cgroup people have an opinion?
No strong opinions either way at my end.
-- Three Cheers, Balbir
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