From: Anthony Liguori <anthony@codemonkey.ws>
To: Christoph Hellwig <hch@lst.de>
Cc: Kevin Wolf <kwolf@redhat.com>,
devin122@gmail.com, Stefan Hajnoczi <stefanha@gmail.com>,
Jagane Sundar <jagane@sundar.org>, Dor Laor <dlaor@redhat.com>,
qemu-devel <qemu-devel@nongnu.org>,
Markus Armbruster <armbru@redhat.com>,
Feiran Zheng <famcool@gmail.com>,
Frediano Ziglio <freddy77@gmail.com>,
Jes Sorensen <Jes.Sorensen@redhat.com>,
Paolo Bonzini <pbonzini@redhat.com>
Subject: Re: [Qemu-devel] Block layer roadmap
Date: Thu, 28 Jul 2011 07:52:24 -0500 [thread overview]
Message-ID: <4E315B88.8080104@codemonkey.ws> (raw)
In-Reply-To: <20110728120931.GB17045@lst.de>
On 07/28/2011 07:09 AM, Christoph Hellwig wrote:
> On Wed, Jul 27, 2011 at 01:37:31PM +0100, Stefan Hajnoczi wrote:
>> Coroutines in the block layer [Kevin]
>> * Programming model to simplify block drivers without blocking QEMU threads
>
> Can anyone explain what the whole point of this is? It really just is
> a bit of syntactic sugar for the current async state machines. What does
> it buy us over going for real threading?
It is threading--just with a common locking model where a single big
lock is held to make up for the fact that most of QEMU isn't reentrant.
By restructuring the code to be threaded, we can incrementally remove
the big lock if we audit for use of non-reentrant functions and
introduce more granular locking.
The whole ucontext/setjmp thing is just an optimization. I would hope
it entirely disappears long term as we promote coroutines to full threads.
Regards,
Anthony Liguori
>
>
next prev parent reply other threads:[~2011-07-28 12:52 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-07-27 12:37 [Qemu-devel] Block layer roadmap Stefan Hajnoczi
2011-07-27 12:50 ` Anthony Liguori
2011-07-28 10:05 ` Kevin Wolf
2011-07-28 12:08 ` Christoph Hellwig
2011-07-28 12:29 ` Kevin Wolf
2011-07-28 10:52 ` Stefan Hajnoczi
2011-07-28 12:09 ` Christoph Hellwig
2011-07-28 12:15 ` Frediano Ziglio
2011-07-28 12:16 ` Christoph Hellwig
2011-07-28 12:35 ` Kevin Wolf
2011-07-28 12:54 ` Stefan Hajnoczi
2011-07-28 13:10 ` Kevin Wolf
2011-07-28 13:11 ` Stefan Hajnoczi
2011-07-28 12:52 ` Anthony Liguori [this message]
2011-07-29 12:35 ` Stefan Hajnoczi
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