lkml.org 
[lkml]   [2021]   [Jan]   [26]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH] perf/intel: Remove Perfmon-v4 counter_freezing support
From
Date
On 11/11/20 03:42, Xu, Like wrote:
> Hi Peter,
>
> On 2020/11/11 4:52, Stephane Eranian wrote:
>> On Tue, Nov 10, 2020 at 7:37 AM Peter Zijlstra<peterz@infradead.org>
>> wrote:
>>> On Tue, Nov 10, 2020 at 04:12:57PM +0100, Peter Zijlstra wrote:
>>>> On Mon, Nov 09, 2020 at 10:12:37AM +0800, Like Xu wrote:
>>>>> The Precise Event Based Sampling(PEBS) supported on Intel Ice Lake
>>>>> server
>>>>> platforms can provide an architectural state of the instruction
>>>>> executed
>>>>> after the instruction that caused the event. This patch set enables
>>>>> the
>>>>> the PEBS via DS feature for KVM (also non) Linux guest on the Ice
>>>>> Lake.
>>>>> The Linux guest can use PEBS feature like native:
>>>>>
>>>>>    # perf record -e instructions:ppp ./br_instr a
>>>>>    # perf record -c 100000 -e instructions:pp ./br_instr a
>>>>>
>>>>> If the counter_freezing is not enabled on the host, the guest PEBS
>>>>> will
>>>>> be disabled on purpose when host is using PEBS facility. By default,
>>>>> KVM disables the co-existence of guest PEBS and host PEBS.
> Thanks Stephane for clarifying the use cases for Freeze-on-[PMI|Overflow].
>
> Please let me express it more clearly.
>
> The goal of the whole patch set is to enable guest PEBS, regardless of
> whether the counter_freezing is frozen or not. By default, it will not
> support both the guest and the host to use PEBS at the same time.
>
> Please continue reviewing the patch set, especially for the slow path
> we proposed this time and related host perf changes:
>
> - add intel_pmu_handle_guest_pebs() to __intel_pmu_pebs_event();
> - add switch MSRs (PEBS_ENABLE, DS_AREA, DATA_CFG) to
> intel_guest_get_msrs();
> - the construction of incoming parameters for
> perf_event_create_kernel_counter();
>
> I believe if you understand the general idea, the comments will be very
> valuable.

What is the state of this work? I was expecting a new version that
doesn't use counter_freezing. However, I see that counter_freezing is
still in there, so this patch from Peter has never been applied.

Paolo

\
 
 \ /
  Last update: 2021-01-26 12:32    [W:0.127 / U:1.144 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site