From: Peter Xu <peterx@redhat.com>
To: Stefan Hajnoczi <stefanha@redhat.com>
Cc: Stefan Hajnoczi <stefanha@gmail.com>,
Luiz Capitulino <lcapitulino@redhat.com>,
kvm@vger.kernel.org, yoshihiro.yunomae.ez@hitachi.com,
mtosatti@redhat.com, qemu-devel@nongnu.org, rostedt@goodmis.org,
linux-trace-users@vger.kernel.org, pbonzini@redhat.com
Subject: Re: [Qemu-devel] [RFC] host and guest kernel trace merging
Date: Fri, 25 Mar 2016 10:22:03 +0800 [thread overview]
Message-ID: <20160325022203.GG28183@pxdev.xzpeter.org> (raw)
In-Reply-To: <20160324101317.GB21069@stefanha-x1.localdomain>
On Thu, Mar 24, 2016 at 10:13:17AM +0000, Stefan Hajnoczi wrote:
> There are probably race conditions if the tsc offset is queried
> independently from the trace collection. For example, imagine the host
> is suspend right when tracing begins. I think the TSC could be adjusted
> when the host wakes up again.
Right... So maybe we should never allow tsc-offset change
(e.g. suspend) happen during host-guest tracing? It seems more like
a question about "whether we can do a merge", rather than "read a
correct offset"... If it changes, we cannot do the merge any more
(only if we record the offset for each guest entry)...
>
> Ideally the TSC information would be part of the trace data so that
> there are no race conditions when interpeting time stamps.
Agree. We should keep the tsc-offset in the trace data.
Thanks.
-- peterx
WARNING: multiple messages have this Message-ID (diff)
From: Peter Xu <peterx@redhat.com>
To: Stefan Hajnoczi <stefanha@redhat.com>
Cc: kvm@vger.kernel.org, Stefan Hajnoczi <stefanha@gmail.com>,
yoshihiro.yunomae.ez@hitachi.com, mtosatti@redhat.com,
qemu-devel@nongnu.org, rostedt@goodmis.org,
Luiz Capitulino <lcapitulino@redhat.com>,
linux-trace-users@vger.kernel.org, pbonzini@redhat.com
Subject: Re: [Qemu-devel] [RFC] host and guest kernel trace merging
Date: Fri, 25 Mar 2016 10:22:03 +0800 [thread overview]
Message-ID: <20160325022203.GG28183@pxdev.xzpeter.org> (raw)
In-Reply-To: <20160324101317.GB21069@stefanha-x1.localdomain>
On Thu, Mar 24, 2016 at 10:13:17AM +0000, Stefan Hajnoczi wrote:
> There are probably race conditions if the tsc offset is queried
> independently from the trace collection. For example, imagine the host
> is suspend right when tracing begins. I think the TSC could be adjusted
> when the host wakes up again.
Right... So maybe we should never allow tsc-offset change
(e.g. suspend) happen during host-guest tracing? It seems more like
a question about "whether we can do a merge", rather than "read a
correct offset"... If it changes, we cannot do the merge any more
(only if we record the offset for each guest entry)...
>
> Ideally the TSC information would be part of the trace data so that
> there are no race conditions when interpeting time stamps.
Agree. We should keep the tsc-offset in the trace data.
Thanks.
-- peterx
next prev parent reply other threads:[~2016-03-25 2:22 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-03-03 19:35 [RFC] host and guest kernel trace merging Luiz Capitulino
2016-03-03 19:35 ` [Qemu-devel] " Luiz Capitulino
2016-03-04 11:19 ` Stefan Hajnoczi
2016-03-04 13:23 ` Steven Rostedt
2016-03-04 13:23 ` Steven Rostedt
2016-03-04 13:23 ` Steven Rostedt
2016-03-07 15:17 ` [Qemu-devel] " Stefan Hajnoczi
2016-03-07 15:17 ` Stefan Hajnoczi
2016-03-07 15:49 ` Steven Rostedt
2016-03-07 15:49 ` Steven Rostedt
2016-03-07 16:10 ` Eric Blake
2016-03-07 16:26 ` Steven Rostedt
2016-03-07 16:26 ` Steven Rostedt
2016-03-07 17:13 ` Paolo Bonzini
2016-03-07 17:13 ` Paolo Bonzini
2016-03-24 5:16 ` Peter Xu
2016-03-24 5:16 ` Peter Xu
2016-03-24 13:02 ` Luiz Capitulino
2016-03-24 13:02 ` Luiz Capitulino
2016-03-25 1:53 ` Peter Xu
2016-03-25 1:53 ` Peter Xu
2016-03-24 8:42 ` Peter Xu
2016-03-24 8:42 ` Peter Xu
2016-03-24 10:13 ` Stefan Hajnoczi
2016-03-24 10:13 ` Stefan Hajnoczi
2016-03-25 2:22 ` Peter Xu [this message]
2016-03-25 2:22 ` Peter Xu
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