On Wed, Mar 25, 2015 at 01:55:44PM -0600, David Ahern wrote: > On 3/25/15 1:15 PM, Don Zickus wrote: > >On Wed, Mar 25, 2015 at 10:51:10AM -0600, David Ahern wrote: > >>363b785f38 added synthesized fork events and set a thread's parent id > >>to itself. Since we are already processing /proc/<pid>/status the ppid > >>can be determined properly. Make it so. > >> > >>Performance impact measured on a sparc based T5-8 (1024 CPUs): > >>$ ps -efL | wc -l > >>20185 > >> > >>Current code: > >>$ time perf record -o perf-no-ppid.data -e cpu-clock -F 1000 -a -v -BN -- > >>usleep 1 > >>mmap size 532480B > >>[ perf record: Woken up 0 times to write data ] > >>failed to write feature 9 > >>[ perf record: Captured and wrote 0.000 MB perf-no-ppid.data ] > >> > >>real 0m26.144s > >>user 0m0.452s > >>sys 0m25.564s > >> > >>With PPID patch: > >>$ time ./perf_ppid record -o perf-ppid.data -e cpu-clock -F 1000 -a -v -BN > >>-- usleep 1 > >>mmap size 532480B > >>[ perf record: Woken up 0 times to write data ] > >>failed to write feature 9 > >>[ perf record: Captured and wrote 0.000 MB perf-ppid.data ] > >> > >>real 0m25.743s > >>user 0m0.268s > >>sys 0m25.368s > >> > >>Signed-off-by: David Ahern <dsah...@gmail.com> > >>Cc: Don Zickus <dzic...@redhat.com> > >>Cc: Joe Mario <jma...@redhat.com> > >>Cc: Jiri Olsa <jo...@redhat.com> > >>--- > >>v2: > >>- removed loop in place of 1 read and processing a buffer > > > >Hmm, I am not entirely sure this is correct. You made an optimization that > >hides the negative impact your patch does. I would prefer you split this > >patch into two pieces. One with the read loop optimization (which I think > >is great) and the second is your ppid change. > > > >I would then like to redo our test with the first patch applied and then > >both patches applied. > > > > From your other response I take it you understand the patch now? It > is a matter of semantics to break this single into 2 -- optimize the > existing code and then add the ppid. End result will be what this > patch shows. Before I do that can you /Joe confirm the performance > is acceptable?
Yes. I believe Joe will try to find time on Thursday to run this. Cheers, Don -- 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/
