On Thu, Oct 23, 2014 at 10:53 AM, Peter Zijlstra <[email protected]> wrote: > On Wed, Oct 22, 2014 at 11:04:31PM +0200, Stephane Eranian wrote: >> Here is a simple case: >> Limiting each HT to only 2 counters, can be any, 2 out of 4 possible. >> >> HT0: you measure a MEM* in ctr2, it is started first, and it keeps running >> HT1: you measure PREC_DIST with PEBS (it requires ctr2) >> >> HT0 is measuring a corrupting event on ctr2, this prevents ctr2 on HT1 >> from being used. >> HT1 is starved, it cannot measure PREC_DIST >> >> Yes you have a quota of 2 out of 4 counters. >> >> The quota dynamic or static can help mitigate the starvation. The only >> way to eliminate >> it is to force multiplexing even though you are using fewer counters >> than actually avail. > > Ah yes, the very narrowly constrained events. Those suck indeed. And I > imagine rotation might not even help here -- rotation doesn't guarantee > SMT1 will try and schedule before SMT0, in fact there are setups > (staggered tick) where its almost guaranteed not to. > > Still I suppose for 'normal' event its a much better state, SMT1 can > always schedule some events.
Yes, I agree with you. The soft partition helps. I will add that in V3. Thanks. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
