Messages in this thread | | | Date | Thu, 27 Jun 2013 13:18:54 +1000 | From | Michael Ellerman <> | Subject | Re: [PATCH 15/15] perf, tools: Add perf stat --transaction v3 |
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On Wed, Jun 19, 2013 at 04:46:21PM +0200, Andi Kleen wrote: > > This hard coded list isn't going to work for us on powerpc. > > > > We don't have HLE, so we won't ever have an event for el-start. > > > > I don't quite grok what the cycles-ct is about, checkpointed cycles? > > The counter is check pointed on a transaction start, and set back to > the checkpoint when an abort happens. This allows to count the cycles > wasted in aborts, when you subtract from cycles-t.
OK. I'm still confused by that one sorry. In the patch you do:
+ else if (perf_evsel__cmp(counter, nth_evsel(T_CYCLES_IN_TX_CP))) + update_stats(&runtime_cycles_in_txcp_stats[0], count[0]);
But then I don't see where you use runtime_cycles_in_txcp_stats ?
> > But I don't think we have anything equivalent. > > But you have cycles-t and tx-start?
We have: - cycles - cycles in transactional state - cycles spent in successful transactions
So your cycles-t is "cycles in transactional state".
We would calculate cycles wasted in aborts with:
"cycles in transactional" - "cycles in successful transactions"
Which I think is what you're describing above with cycles-ct.
Does "tx-start" just count the number of transactions begun? Does it count nested transactions?
We have one counter for non-nested transactions and one for nested, but I think we could just count the non-nested as "tx-start", that's probably of most interest.
> > I guess the simplest option is to make it a per-arch list inside the > > perf tool? > > I'm not sure that would be acceptable to the perf maintainers. > Although I'm just guessing, I haven't heard any comments on > this patch recently.
Yeah sure. Although I agree with the desire to make the perf tool work similarly across architectures, I think as we add more of these detailed analysis tools we are eventually going to come across something that can't be handled generically. But I guess we'll see.
cheers
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