On Wed, Feb 20, 2013 at 12:55:59PM -0800, Andi Kleen wrote: > Jiri Olsa <jo...@redhat.com> writes: > > > Changing the default 'instructions' HW event for SandyBridge and > > IvyBrige to use the available precise 'instructions' event. > > > > The precise event is defined in Intel SDM as: > > > > INST_RETIRED.ALL - Precise instruction retired event with HW to > > reduce effect of PEBS shadow in IP distribution > > > > for both SandyBridge and IvyBrige micro-archs. It allows to use > > precise modifier on 'instructions' event on SandyBridge and > > IvyBrige micro-archs which is not possible now. > > Actually it's possible, you just have to use it explicitely. > > This will break a lot of profiling setups that assume instructions > count on the fixed counter and use the 4/8 other counters. > Also it will give very bad results with perf stat, which > you don't want to run with pebs.
right, I haven't realized that.. > > Even worse with your change the fixed instruction counter is not > accessible anymore. So pretty much all the standard setups still could be used explicitly via cpu/event=0xc0/ > that collect it in addition to other events and fill all > the counters would break. > > I don't think it should be done by default, but yes explicitely > it's quite useful. > > My Haswell patchkit (in the "extended version") exposes > the precise event as "instructions-p" through sysfs. will check thanks, jirka -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
