From: Marc Zyngier <maz@kernel.org>
To: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Cc: Mark Rutland <mark.rutland@arm.com>,
Mathieu Poirier <mathieu.poirier@linaro.org>,
Peter Zijlstra <peterz@infradead.org>,
John Garry <john.garry@huawei.com>,
linux-kernel@vger.kernel.org,
Arnaldo Carvalho de Melo <acme@kernel.org>,
Suleiman Souhlal <suleiman@google.com>,
Leo Yan <leo.yan@linaro.org>, Namhyung Kim <namhyung@kernel.org>,
Will Deacon <will@kernel.org>,
linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCHv3] perf kvm: add kvm-stat for arm64
Date: Fri, 18 Sep 2020 11:55:56 +0100 [thread overview]
Message-ID: <06c3e5d907d1145bf3a7a03de63170ae@kernel.org> (raw)
In-Reply-To: <20200918103521.GE3049@jagdpanzerIV.localdomain>
On 2020-09-18 11:35, Sergey Senozhatsky wrote:
> On (20/09/18 09:20), Marc Zyngier wrote:
>> On 2020-09-18 01:32, Sergey Senozhatsky wrote:
>> > On (20/09/17 12:53), Marc Zyngier wrote:
>> > > Feel free to add a *new* tracepoint instead.
>> >
>> > Wouldn't we want a whole bunch of new tracepoints in this case?
>>
>> Yes. I don't have a better solution as long as tracepoints are ABI.
>
> Well, no one does.
>
>> Get someone to sign-off on it, and I'll happily change them.
>
> Sorry, I'm not sure I understand this sentence.
What I meant is that the only way to make changes to existing
tracepoints
would be to get someone like Linus to approve them.
It's all rhetorical anyway, so let's move on.
>
>> > (almost all of the existing ones with the extra vcpu_id field).
>> > Right now we have 3 types of events:
>> > - events with no vcpu at all // nil
>> > - events with vcpu_pc // "0x%016lx", __entry->vcpu_pc
>> > - events with (void *)vcpu // "vcpu: %p", __entry->vcpu
>> >
>> > It might be helpful if we could filter out events by vcpu_id.
>> > But this, basically, doubles the number of events in the ringbuffer.
>>
>> Only if you enable them both, right?
> [..]
>> How would that double the number of events in the buffer?
>
> Yes. I assume that many scripts do something like "capture kvm:*
> events",
> so new and old events are enabled. Unless we want to keep new events in
> something like kvm2:* namespace (which is unlikely to happen, I guess).
I really don't mind. I actually like the namespacing, as it gives us
a notion of versioning, something tracepoints lack.. And it gives an
opportunity to argue about the name of the namespace.
>
> And `sudo ./perf stat -e 'kvm:*'` is not unseen. In fact, this is
> literally the first thing mentioned at
> https://www.linux-kvm.org/page/Perf_events
>
> So if we'll have something like
>
> trace_kvm_foo(vcpu);
> + trace_kvm_foo2(vcpu->id, vcpu);
>
> for all arm64 kvm events, then we double the number of arm64 kvm:*
> events
> in the ringbuffer, don't we? Maybe this is not a gigantic issue, but
> who
> knows.
I don't think it's a problem, but I'm more in favour of the namespace
approach.
M.
--
Jazz is not dead. It just smells funny...
_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
prev parent reply other threads:[~2020-09-18 10:57 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-17 0:36 [PATCHv3] perf kvm: add kvm-stat for arm64 Sergey Senozhatsky
2020-09-17 8:47 ` Leo Yan
2020-09-17 9:54 ` Sergey Senozhatsky
2020-09-17 10:09 ` Leo Yan
2020-09-17 10:12 ` Leo Yan
2020-09-17 10:21 ` Marc Zyngier
2020-09-17 11:00 ` Sergey Senozhatsky
2020-09-17 13:08 ` Leo Yan
2020-09-17 11:42 ` Leo Yan
2020-09-17 11:53 ` Marc Zyngier
2020-09-17 12:52 ` Leo Yan
2020-09-18 0:32 ` Sergey Senozhatsky
2020-09-18 8:20 ` Marc Zyngier
2020-09-18 10:35 ` Sergey Senozhatsky
2020-09-18 10:55 ` Marc Zyngier [this message]
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=06c3e5d907d1145bf3a7a03de63170ae@kernel.org \
--to=maz@kernel.org \
--cc=acme@kernel.org \
--cc=john.garry@huawei.com \
--cc=leo.yan@linaro.org \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=linux-kernel@vger.kernel.org \
--cc=mark.rutland@arm.com \
--cc=mathieu.poirier@linaro.org \
--cc=namhyung@kernel.org \
--cc=peterz@infradead.org \
--cc=sergey.senozhatsky@gmail.com \
--cc=suleiman@google.com \
--cc=will@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).