From: Adrian Hunter <adrian.hunter@intel.com>
To: Andi Kleen <ak@linux.intel.com>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>,
Jiri Olsa <jolsa@redhat.com>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 11/12] perf intel-pt: Add VM Time Correlation to decoder
Date: Fri, 30 Apr 2021 08:02:14 +0300 [thread overview]
Message-ID: <4f9b20f7-566b-9e32-e9b9-bf6d11ef5d9f@intel.com> (raw)
In-Reply-To: <20210429212140.GE4032392@tassilo.jf.intel.com>
On 30/04/21 12:21 am, Andi Kleen wrote:
>> unchanging (during perf record) VMX TSC Offset and no VMX TSC scaling.
>
> For TSC scaling we would need to add side band to KVM, correct?
>
> I suppose it shouldn't be that hard to do that.
>
Probably we just need to know a single TSC scaling value per VM i.e. it could just be exported via sysfs or something.
There is a reasonable reason that TSC Offset might be changing i.e. to match Guest time, although that seems to be done by paravirtualization instead at the moment.
At the moment TSC Offset does change if Host time changes e.g. Guest has state saved before a Host reboot, and is resumed after the Host reboot
However, I can't think of a reason for changing the TSC Scaling value, except maybe if the VM is taken to a Host with a different TSC frequency.
next prev parent reply other threads:[~2021-04-30 5:01 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-29 12:58 [PATCH 00/12] perf intel-pt: Add more support for VMs Adrian Hunter
2021-04-29 12:58 ` [PATCH 01/12] perf auxtrace: Add Z itrace option for timeless decoding Adrian Hunter
2021-04-29 12:58 ` [PATCH 02/12] perf intel-pt: Move synth_opts initialization earlier Adrian Hunter
2021-04-29 12:58 ` [PATCH 03/12] perf intel-pt: Support Z itrace option for timeless decoding Adrian Hunter
2021-04-29 12:58 ` [PATCH 04/12] perf inject: Add facility to do in place update Adrian Hunter
2021-04-29 14:31 ` Arnaldo Carvalho de Melo
2021-04-29 16:00 ` Andi Kleen
2021-04-29 16:22 ` Adrian Hunter
2021-04-29 12:58 ` [PATCH 05/12] perf inject: Add --vm-time-correlation option Adrian Hunter
2021-04-29 18:46 ` Andi Kleen
2021-04-29 12:58 ` [PATCH 06/12] perf auxtrace: Allow buffers to be mapped read / write Adrian Hunter
2021-04-29 12:58 ` [PATCH 07/12] perf intel-pt: Let overlap detection handle VM timestamps Adrian Hunter
2021-04-29 12:58 ` [PATCH 08/12] perf intel-pt: Add a tree for VMCS information Adrian Hunter
2021-04-29 14:39 ` Arnaldo Carvalho de Melo
2021-04-29 12:58 ` [PATCH 09/12] perf intel-pt: Pass the first timestamp to the decoder Adrian Hunter
2021-04-29 12:58 ` [PATCH 10/12] perf intel-pt: Better 7-byte timestamp wraparound logic Adrian Hunter
2021-04-29 12:58 ` [PATCH 11/12] perf intel-pt: Add VM Time Correlation to decoder Adrian Hunter
2021-04-29 21:21 ` Andi Kleen
2021-04-30 5:02 ` Adrian Hunter [this message]
2021-04-29 12:58 ` [PATCH 12/12] perf intel-pt: Parse VM Time Correlation options and set up decoding Adrian Hunter
2021-04-29 21:24 ` Andi Kleen
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