Messages in this thread | | | Date | Mon, 29 May 2017 17:29:31 +0200 | From | Peter Zijlstra <> | Subject | Re: [PATCH]: perf/core: addressing 4x slowdown during per-process profiling of STREAM benchmark on Intel Xeon Phi |
| |
On Mon, May 29, 2017 at 05:22:54PM +0200, Peter Zijlstra wrote: > On Mon, May 29, 2017 at 04:43:09PM +0300, Alexey Budankov wrote: > > On 29.05.2017 15:03, Alexander Shishkin wrote: > > > Alexey Budankov <alexey.budankov@linux.intel.com> writes: > > > > > + } else if (event->cpu > node_event->cpu) { > > > > + node = &((*node)->rb_right); > > > > + } else { > > > > + list_add_tail(&event->group_list_entry, > > > > + &node_event->group_list); > > > > > > So why is this better than simply having per-cpu event lists plus one > > > for per-thread events? > > > > Good question. Choice of data structure and layout depends on the operations > > applied to the data so keeping groups as a tree simplifies and improves the > > implementation in terms of scalability and performance. Please ask more if > > any. > > Since these lists are per context, and each task can have a context, > you'd end up with per-task-per-cpu memory, which is something we'd like > to avoid (some archs have very limited per-cpu memory space etc..). > > Also, we'd like to have that tree for other reasons, like for instance > that heterogeneous PMU crud ARM has. Also, with a tree we can easier do > time based round-robin scheduling, >
Oh and in general multi-PMU stuff, aside from hetero PMU becomes much easier.
| |