Messages in this thread | | | From | Ulrich Drepper <> | Date | Sun, 27 May 2012 03:56:22 -0400 | Subject | Re: [RFCv2 0/8] perf tool: Add new event group management |
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On Sat, May 26, 2012 at 8:38 AM, Jiri Olsa <jolsa@redhat.com> wrote: > If you have some ideas on this or real world examples, > that would really help.. so far, here's the latest discussion: > http://marc.info/?t=133357436900005&r=1&w=2
If you're looking for a definitive source, just point to the Intel optimization manual. Absolute values of counters are not really useful and so they are defining many (50+) ratios which people should investigate. These ratios are only really accurate if the counters are swapped in and out at the same time.
The reminds me of a detail I looked at when starting an an implementation for this (glad you got more time to devote to it). The problem with ratios are that there are so many. So efficient scheduling is going to be important. Many ratios use as a base the same counters over and over again (e.g., cycle count, instruction count, etc). Therefore it is important to recognize when two groups can be scheduled concurrently even if the total number of counters needed would be high but due to intersections it is possible.
One last comment, not critical. From a parsing point of view the colon in the proposed syntax
name : { counter1, counter2 }
is unnecessary. Just one more thing people can get wrong. How about leaving it out? An open curly brace to indicate a group should be sufficient.
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