linux-kernel - Re: Re: [RFC PATCH 0/6] virtio-trace: Support virtio-trace

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <500E810A.4030309@hitachi.com>
Date:	Tue, 24 Jul 2012 20:03:38 +0900
From:	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
To:	Stefan Hajnoczi <stefanha@...il.com>
Cc:	Yoshihiro YUNOMAE <yoshihiro.yunomae.ez@...achi.com>,
	linux-kernel@...r.kernel.org,
	Herbert Xu <herbert@...dor.apana.org.au>,
	Arnd Bergmann <arnd@...db.de>,
	Frederic Weisbecker <fweisbec@...il.com>,
	yrl.pp-manager.tt@...achi.com, qemu-devel@...gnu.org,
	Borislav Petkov <bp@...64.org>,
	virtualization@...ts.linux-foundation.org,
	"Franch Ch. Eigler" <fche@...hat.com>,
	Ingo Molnar <mingo@...hat.com>,
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Anthony Liguori <anthony@...emonkey.ws>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Amit Shah <amit.shah@...hat.com>,
	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>,
	Dhaval Giani <dhaval.giani@...il.com>
Subject: Re: Re: [RFC PATCH 0/6] virtio-trace: Support virtio-trace

(2012/07/24 19:02), Stefan Hajnoczi wrote:
> On Tue, Jul 24, 2012 at 3:36 AM, Yoshihiro YUNOMAE
> <yoshihiro.yunomae.ez@...achi.com> wrote:
>> The performance of each method is compared as follows:
>>  [1] Native
>>      - only recording trace data to ring-buffer on a guest
>>  [2] Virtio-trace
>>      - running a trace agent on a guest
>>      - a reader on a host opens FIFO using cat command
>>  [3] IVRing
>>      - A SystemTap script in a guest records trace data to IVRing.
>>        -- probe points are same as ftrace.
>>  [4] Virtio-serial(normal)
>>      - A reader(using cat) on a guest output trace data to a host using
>>        standard output via virtio-serial.
> 
> The first time I read this I thought you are adding a new virtio-trace
> device.  But it looks like this series really add splice support to
> virtio-console and that yields a big performance improvement when
> sending trace_pipe_raw.

Yes, sorry for the confusion. Actually this is an enhancement of
virtio-serial. I'm working with Yoshihiro on this feature.

> Guest ftrace is useful and I like this.  Have you thought about
> controlling ftrace from the host?  Perhaps a command could be added to
> the QEMU guest agent which basically invokes trace-cmd/perf.

As you can see, guest trace-agent can be controlled via a
control channel. In our scenario, host tools can control that
instead of guest one.

We are considering that exporting the tracing part of guest's
debugfs to host via another virtio-serial channel by using
9pfs, so that the host tools can refer that.

(In this scenario, guest trace-agent will also provide 9pfs server.
Since it means that the agent can handle writing a special file,
trace-agent can be controlled via the special file on exported
debugfs.)

Of course, this also requires modifying trace-cmd/perf to accept
some options like guest-debugfs mount point, guest's serial
channel pipe (or unix socket?), etc. However, it will be a small
change.

Thank you,

-- 
Masami HIRAMATSU
Software Platform Research Dept. Linux Technology Center
Hitachi, Ltd., Yokohama Research Laboratory
E-mail: masami.hiramatsu.pt@...achi.com
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/