Messages in this thread | | | Date | Fri, 23 Dec 2011 15:40:40 +0100 | From | Ingo Molnar <> | Subject | Re: [PATCH 4/4] perf script: Add script to collect and display IBS samples |
| |
* Peter Zijlstra <peterz@infradead.org> wrote:
> On Fri, 2011-12-23 at 14:53 +0100, Ingo Molnar wrote: > > * Robert Richter <robert.richter@amd.com> wrote: > > > > > > Also, could you quote example output of "perf script report > > > > ibs"? > > > > > > IBS_FETCH sample on cpu6 IBS0: 0x00170003186a186a IBS1: 0x0000000000444780 IBS2:0x000000041af26780 > > > IBS_FETCH sample on cpu6 IBS0: 0x00170003186a186a IBS1: 0x00007f5efb44e3b2 IBS2:0x000000042fcff3b2 > > > IBS_FETCH sample on cpu6 IBS0: 0x01370003186a186a IBS1: 0xffffffff81065273 IBS2:0x0000000001065273 > > > IBS_FETCH sample on cpu6 IBS0: 0x01370003186a186a IBS1: 0xffffffff811a6320 IBS2:0x00000000011a6320 > > > IBS_FETCH sample on cpu6 IBS0: 0x01370003186a186a IBS1: 0xffffffff81065255 IBS2:0x0000000001065255 > > > IBS_FETCH sample on cpu7 IBS0: 0x00170004186a186a IBS1: 0x00007fbf0c687ca0 IBS2:0x000000041d345ca0 > > > IBS_FETCH sample on cpu7 IBS0: 0x00170003186a186a IBS1: 0x000000000043bb80 IBS2:0x000000041c351b80 > > > IBS_FETCH sample on cpu7 IBS0: 0x01370003186a186a IBS1: 0xffffffff813d5790 IBS2:0x00000000013d5790 > > > IBS_FETCH sample on cpu7 IBS0: 0x00030001186a186a IBS1: 0xffffffff8102bd00 IBS2:0x00000000013d5d00 > > > > That does not look very usable to users. So why should we merge > > this new ABI in its incomplete form with no complete usecase? > > Being usable is clearly not outside the scope of a new feature > > ... > > > > Integrating it into perf report should not be *that* hard, > > you've done most of the hard work already. But without that > > step we just don't know how complete and usable the whole > > thing is. > > perf annotate like output might make more sense for IBS, maybe > not decode all the information that's in there, but at least a > number of the most useful measurements for each type and > present multiple columns in front of the instructions. > > Ingo, the trouble with IBS is that it doesn't measure > something, its a measure everything together like thing, so > what particular part of this massive bulk data do you use to > create your histograms?
My point is that a useful angle to it has to be presented for it to be useful for upstream.
The bit that looks useful about IBS is skid-free sampling. So as long as the 'bulk data' contains enough information to do a 'perf record -e instructions:p' work-alike thing it would be useful, right?
Sadly precise cycles sampling is not possible via IBS, right?
Thanks,
Ingo
[*] Sidenote: i suspect the RIP+1 sampling artifact cannot be gotten rid of on AMD CPUs, right?
| |