On Wed, May 20, 2015 at 03:52:09PM +0200, Peter Zijlstra wrote: > On Wed, May 20, 2015 at 11:28:42AM +0200, Peter Zijlstra wrote: > > > --- > > > > c02cdbf60b51b8d98a49185535f5d527a2965142 is the first bad commit > > commit c02cdbf60b51b8d98a49185535f5d527a2965142 > > Author: Stephane Eranian <[email protected]> > > Date: Mon Nov 17 20:07:02 2014 +0100 > > > > perf/x86/intel: Limit to half counters when the HT workaround is > > enabled, to avoid exclusive mode starvation > > > > This patch limits the number of counters available to each CPU when > > the HT bug workaround is enabled. > > > > This is necessary to avoid situation of counter starvation. Such can > > arise from configuration where one HT thread, HT0, is using all 4 > > counters > > with corrupting events which require exclusion the the sibling HT, HT1. > > > > In such case, HT1 would not be able to schedule any event until HT0 > > is done. To mitigate this problem, this patch artificially limits > > the number of counters to 2. > > > > That way, we can gurantee that at least 2 counters are not in exclusive > > mode and therefore allow the sibling thread to schedule events of the > > same type (system vs. per-thread). The 2 counters are not determined > > in advance. We simply set the limit to two events per HT. > > > > This helps mitigate starvation in case of events with specific counter > > constraints such a PREC_DIST. > > > > Note that this does not elimintate the starvation is all cases. But > > it is better than not having it. > > > > (Solution suggested by Peter Zjilstra.) > > > > Signed-off-by: Stephane Eranian <[email protected]> > > Signed-off-by: Peter Zijlstra (Intel) <[email protected]> > > Cc: [email protected] > > Cc: [email protected] > > Cc: [email protected] > > Cc: [email protected] > > Link: > > http://lkml.kernel.org/r/[email protected] > > Signed-off-by: Ingo Molnar <[email protected]> > > OK, so if you have the watchdog enabled, that's 1 event, and having a > max of 2 GP events, adding another 2 events is fail. > > Jiri, did you SNB have the watchdog disabled?
watchdog was enabled jirka -- 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/
