Messages in this thread | | | Date | Tue, 16 Mar 2010 10:34:40 +0100 | From | Ingo Molnar <> | Subject | Re: [RFC] [PATCH 1/1] perf: add support for arch-dependent symbolic event names to "perf stat" |
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* Paul Mackerras <paulus@samba.org> wrote:
> On Thu, Mar 11, 2010 at 01:46:08PM +0100, Ingo Molnar wrote: > > > > * Corey Ashford <cjashfor@linux.vnet.ibm.com> wrote: > > > > > On 3/3/2010 6:30 PM, Corey Ashford wrote: > > > >For your review, this patch adds support for arch-dependent symbolic > > > >event names to the "perf stat" tool, and could be expanded to other > > > >"perf *" commands fairly easily, I suspect. > > > I'm quite much against stop-gap measures like this - they tend to become > > tomorrow's impossible-to-remove quirk. > > > > If you want extensible events you can already do it by providing an ftrace > > tracepoint event via TRACE_EVENT. They are easy to add and ad-hoc, and are > > supported throughout by perf. > > If I've understood correctly what Corey is doing, I think you're missing the > point. The idea, I thought, was to provide a way to be able to use symbolic > names for raw hardware events rather than just numbers. I don't see how > ftrace tracepoint events are relevant to that.
tracepoints are relevant because they are the currently best way of how we assign symbolic names to various kernel-internal events. For ad-hoc usecases like this:
http://dri.freedesktop.org/wiki/IntelPerformanceTuning
I'd much rather see that facility used (and, to the extent needed, extended) to provide support for rare arch events that we dont want to enumerate in a generic way.
Or, if the events are important enough to be hardcoded into the perf ABI itself, they should be generalized in a meaningful way - even if you dont expect them to show up on other CPUs.
Ingo
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