linux-kernel - Re: [PATCH 0/6] perf tools: Add wallclock time conversion support

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Date:   Fri, 31 Jul 2020 08:36:12 -0700
From:   Andi Kleen <ak@...ux.intel.com>
To:     Jiri Olsa <jolsa@...hat.com>
Cc:     David Ahern <dsahern@...il.com>, peterz@...radead.org,
        Jiri Olsa <jolsa@...nel.org>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        lkml <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Michael Petlan <mpetlan@...hat.com>,
        Ian Rogers <irogers@...gle.com>,
        Geneviève Bastien <gbastien@...satic.net>,
        Wang Nan <wangnan0@...wei.com>,
        Jeremie Galarneau <jgalar@...icios.com>
Subject: Re: [PATCH 0/6] perf tools: Add wallclock time conversion support

> yep, we have a customer that needs to compare data from multiple servers

It's also needed to correlate over different guests on the same machine.
This is an important use case.

It would be nice if we could find a way to export the per guest 
TSC offset from KVM, then we could use the more reliable TSC for this,
at least as long as no TSC scaling is used.

But failing that wall clock is probably the best you can do.

-Andi