Hi Peter, On Mon, Dec 14, 2015 at 10:26:13AM +0100, Peter Zijlstra wrote: > On Fri, Dec 11, 2015 at 08:01:31AM -0700, David Ahern wrote: > > On 12/11/15 1:11 AM, Ingo Molnar wrote: > > > > > >* Namhyung Kim <namhy...@gmail.com> wrote: > > > > > >>IIRC David said that thread per cpu seems too much especially on a large > > >>system > > >>(like ~1024 cpu). [...] > > > > > >Too much in what fashion? For recording I think it's the fastest, most > > >natural > > >model - anything else will create cache line bounces. > > > > The intrusiveness of perf on the system under observation. I understand > > there are a lot of factors that go into it. > > So I can see some of that, if every cpu has its own thread then every > cpu will occasionally schedule that thread. Whereas if there were less, > you'd not have that. > > Still, I think it makes sense to implement it, we need the multi-file > option anyway. Once we have that, we can also implement a per-node > option, which should be a fairly simple hybrid of the two approaches. > > The thing is, perf-record is really struggling on big machines.
Yes, but perf-record and perf-top is different. The perf-record merely saves the data into file while perf-top read events and process them at the same time without file. So we should choose different default IMHO. I want to focus on perf-top for now, once it's in a good shape, I'll work on perf record/report too. > > And in an unrelated note, I absolutely detest --buildid being the > default, it makes perf-record blow chunks. Maybe we can add a config option? Thanks, Namhyung -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
