perf_events: Add a helper to search for an event in a context
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From: Frederic Weisbecker on 1 Jul 2010 12:30 On Thu, Jul 01, 2010 at 06:24:24PM +0200, Borislav Petkov wrote: > From: Frederic Weisbecker <fweisbec(a)gmail.com> > Date: Thu, Jul 01, 2010 at 12:14:50PM -0400 > > Hi Frederic, > > > On Thu, Jul 01, 2010 at 06:12:45PM +0200, Peter Zijlstra wrote: > > > On Thu, 2010-07-01 at 18:11 +0200, Frederic Weisbecker wrote: > > > > I suspect we need another syscall that can list all the persistent events > > > > with a unique id and the attrs that follow. > > > > > > > > So you get a unique id for all of them and you can create an fd on top > > > > of this id by using a PERF_FLAG_REQUEST_PERSISTENT and this id put in > > > > attr.config. > > > > > > Isn't that what filesystems were invented for? > > > > > > The problem is when you create a persistent event, you lose the fd. > > So you need to retrieve it somehow. > > actually the idea is to decouple those from the fd alltogether and > provide specific file_operations in debugfs and such, as Peter > suggested. Which sounds much more sane to me especially since, at least > in the MCE case, all the entities that register into that event need to > see the same samples (and read the same buffers etc). Sure the idea of putting that in fs is better. Note the idea of a new syscall was quite close: it would have listed unique ids of the persistent events, but not fds, you'd have yet to create those fds on top of the ids. > > And let's try not to read too much into those persistent events - it may > just as well be that we need them only for MCEs and nothing else :) Not really. It would be useful for boot tracing, amongst various other things like flight recorder tracing, etc... -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ |