From: Peter Zijlstra <peterz@infradead.org>
To: Wei Wang <wei.w.wang@intel.com>
Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
pbonzini@redhat.com, ak@linux.intel.com, kan.liang@intel.com,
mingo@redhat.com, rkrcmar@redhat.com, like.xu@intel.com,
jannh@google.com, arei.gonglei@huawei.com, jmattson@google.com
Subject: Re: [PATCH v7 07/12] perf/x86: no counter allocation support
Date: Tue, 9 Jul 2019 11:43:05 +0200 [thread overview]
Message-ID: <20190709094305.GT3402@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <5D2402E6.7060104@intel.com>
On Tue, Jul 09, 2019 at 10:58:46AM +0800, Wei Wang wrote:
> On 07/08/2019 10:29 PM, Peter Zijlstra wrote:
>
> Thanks for the comments.
>
> >
> > > diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
> > > index 0ab99c7..19e6593 100644
> > > --- a/include/linux/perf_event.h
> > > +++ b/include/linux/perf_event.h
> > > @@ -528,6 +528,7 @@ typedef void (*perf_overflow_handler_t)(struct perf_event *,
> > > */
> > > #define PERF_EV_CAP_SOFTWARE BIT(0)
> > > #define PERF_EV_CAP_READ_ACTIVE_PKG BIT(1)
> > > +#define PERF_EV_CAP_NO_COUNTER BIT(2)
> > > #define SWEVENT_HLIST_BITS 8
> > > #define SWEVENT_HLIST_SIZE (1 << SWEVENT_HLIST_BITS)
> > > @@ -895,6 +896,13 @@ extern int perf_event_refresh(struct perf_event *event, int refresh);
> > > extern void perf_event_update_userpage(struct perf_event *event);
> > > extern int perf_event_release_kernel(struct perf_event *event);
> > > extern struct perf_event *
> > > +perf_event_create(struct perf_event_attr *attr,
> > > + int cpu,
> > > + struct task_struct *task,
> > > + perf_overflow_handler_t overflow_handler,
> > > + void *context,
> > > + bool counter_assignment);
> > > +extern struct perf_event *
> > > perf_event_create_kernel_counter(struct perf_event_attr *attr,
> > > int cpu,
> > > struct task_struct *task,
> > Why the heck are you creating this wrapper nonsense?
>
> (please see early discussions: https://lkml.org/lkml/2018/9/20/868)
> I thought we agreed that the perf event created here don't need to consume
> an extra counter.
That's almost a year ago; I really can't remember that and you didn't
put any of that in your Changelog to help me remember.
(also please use: https://lkml.kernel.org/r/$msgid style links)
> In the previous version, we added a "no_counter" bit to perf_event_attr, and
> that will be exposed to user ABI, which seems not good.
> (https://lkml.org/lkml/2019/2/14/791)
> So we wrap a new kernel API above to support this.
>
> Do you have a different suggestion to do this?
> (exclude host/guest just clears the enable bit when on VM-exit/entry,
> still consumes the counter)
Just add an argument to perf_event_create_kernel_counter() ?
next prev parent reply other threads:[~2019-07-09 9:43 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-08 1:23 [PATCH v7 00/12] Guest LBR Enabling Wei Wang
2019-07-08 1:23 ` [PATCH v7 01/12] perf/x86: fix the variable type of the LBR MSRs Wei Wang
2019-07-08 1:23 ` [PATCH v7 02/12] perf/x86: add a function to get the lbr stack Wei Wang
2019-07-08 1:23 ` [PATCH v7 03/12] KVM/x86: KVM_CAP_X86_GUEST_LBR Wei Wang
2019-07-08 1:23 ` [PATCH v7 04/12] KVM/x86: intel_pmu_lbr_enable Wei Wang
2019-07-08 1:23 ` [PATCH v7 05/12] KVM/x86/vPMU: tweak kvm_pmu_get_msr Wei Wang
2019-07-08 1:23 ` [PATCH v7 06/12] KVM/x86: expose MSR_IA32_PERF_CAPABILITIES to the guest Wei Wang
2019-07-08 1:23 ` [PATCH v7 07/12] perf/x86: no counter allocation support Wei Wang
2019-07-08 14:29 ` Peter Zijlstra
2019-07-09 2:58 ` Wei Wang
2019-07-09 9:43 ` Peter Zijlstra [this message]
2019-07-09 11:36 ` Wei Wang
2019-07-08 1:23 ` [PATCH v7 08/12] KVM/x86/vPMU: Add APIs to support host save/restore the guest lbr stack Wei Wang
2019-07-08 14:48 ` Peter Zijlstra
2019-07-09 3:04 ` Wei Wang
2019-07-09 9:39 ` Peter Zijlstra
2019-07-09 11:34 ` Wei Wang
2019-07-09 12:19 ` Peter Zijlstra
2019-07-10 8:19 ` Wei Wang
2019-07-09 11:45 ` Peter Zijlstra
2019-07-10 8:21 ` Wei Wang
2019-07-08 1:23 ` [PATCH v7 09/12] perf/x86: save/restore LBR_SELECT on vCPU switching Wei Wang
2019-07-08 1:23 ` [PATCH v7 10/12] KVM/x86/lbr: lazy save the guest lbr stack Wei Wang
2019-07-08 14:53 ` Peter Zijlstra
2019-07-08 15:11 ` Andi Kleen
2019-07-09 11:39 ` Peter Zijlstra
2019-07-09 3:14 ` Wei Wang
2019-07-08 1:23 ` [PATCH v7 11/12] KVM/x86: remove the common handling of the debugctl msr Wei Wang
2019-07-08 1:23 ` [PATCH v7 12/12] KVM/VMX/vPMU: support to report GLOBAL_STATUS_LBRS_FROZEN Wei Wang
2019-07-08 15:09 ` Peter Zijlstra
2019-07-09 3:24 ` Wei Wang
2019-07-09 11:35 ` Peter Zijlstra
2019-07-10 9:23 ` Wei Wang
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