On 10/24/2012 08:36 PM, Stephane Eranian wrote: > On Wed, Oct 24, 2012 at 2:31 PM, Andi Kleen <a...@linux.intel.com> wrote: >> On Wed, Oct 24, 2012 at 02:21:43PM +0200, Stephane Eranian wrote: >>> But still, if I do: >>> $ perf record -g -e cpu/cycles/k ........ >>> >>> Looks like your code will activate LBR cstack for user stack even >>> though I don't use it. >>> I know it won't generate any user samples (theoretically) but you are >>> still commandeering >>> the LBR resource which other events may want to use. >> >> You can disable it in sysfs. LBR is a power user feature and they will >> know how to do this. >> > But isn't the whole point of the patch to hide LBR cstack from users so they > won't know they're using it for user cstack? > > To disable it in sysfs, I need to know it's being used in the first place. > You're saying, I need to know it is used only for user cstack and if I don't > need it then I need to disable it explicitly. I also suspect using it > for nothing > may have some performance implication because you are saving/restoring > on ctxsw, for instance. > > I think in x86_pmu_hw_config(), you could simply check the priv level > restrictions on the event. If exclude_user is set, then don't active LBR > cstack > and that's it. That's what I was trying to get to... >
I will add that check Thanks Yan, Zheng -- 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/
