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From: Kevin Wolf <kwolf@redhat.com>
To: "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>
Cc: Blue Swirl <blauwirbel@gmail.com>,
	Anthony Liguori <aliguori@us.ibm.com>,
	Venkateswararao Jujjuri <jvrao@linux.vnet.ibm.com>,
	Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>,
	qemu-devel@nongnu.org
Subject: Re: [Qemu-devel] [PATCH v8 0/5] Coroutines for better asynchronous programming
Date: Wed, 27 Jul 2011 12:03:57 +0200	[thread overview]
Message-ID: <4E2FE28D.5060206@redhat.com> (raw)
In-Reply-To: <8739hs5a6n.fsf@skywalker.in.ibm.com>

Am 27.07.2011 11:45, schrieb Aneesh Kumar K.V:
> On Tue, 26 Jul 2011 10:21:12 +0100, Stefan Hajnoczi <stefanha@linux.vnet.ibm.com> wrote:
>> QEMU is event-driven and suffers when blocking operations are performed because
>> VM execution may be stopped until the operation completes.  Therefore many
>> operations that could block are performed asynchronously and a callback is
>> invoked when the operation has completed.  This allows QEMU to continue
>> executing while the operation is pending.
>>
>> The downside to callbacks is that they split up code into many smaller
>> functions, each of which is a single step in a state machine that quickly
>> becomes complex and hard to understand.  Callback functions also result in lots
>> of noise as variables are packed and unpacked into temporary structs that pass
>> state to the callback function.
>>
>> This patch series introduces coroutines as a solution for writing asynchronous
>> code while still having a nice sequential control flow.  The semantics are
>> explained in the second patch.  The fourth patch adds automated tests.
>>
>> A nice feature of coroutines is that it is relatively easy to take synchronous
>> code and lift it into a coroutine to make it asynchronous.  Work has been done
>> to move qcow2 request processing into coroutines and thereby make it
>> asynchronous (today qcow2 will perform synchronous metadata accesses).  This
>> qcow2 work is still ongoing and not quite ready for mainline yet.
>>
>> v8:
>>  * Bisectability: introduce gthread implementation before ucontext/fibers
> 
> Can we also get CoMutex and CoQueue patches also merged. I use them in
> the VirtFS series. 
> 
> http://repo.or.cz/w/qemu/kevin.git/shortlog/refs/heads/coroutine-devel
> http://repo.or.cz/w/qemu/v9fs.git/commit/318ef0b9b01cd296f8c30d8288139b9bed859892

I introduce these in my block coroutine patches. I posted a RFC last
week and the first "real" patch series yesterday, so I hope they get
review and can be merged into master soon.

Kevin

  reply	other threads:[~2011-07-27 10:01 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2011-07-26  9:21 [Qemu-devel] [PATCH v8 0/5] Coroutines for better asynchronous programming Stefan Hajnoczi
2011-07-26  9:21 ` [Qemu-devel] [PATCH v8 1/5] coroutine: add gthread dependency Stefan Hajnoczi
2011-07-26  9:21 ` [Qemu-devel] [PATCH v8 2/5] coroutine: introduce coroutines API Stefan Hajnoczi
2011-07-26  9:21 ` [Qemu-devel] [PATCH v8 3/5] coroutine: add ucontext and win32 implementations Stefan Hajnoczi
2011-07-26  9:21 ` [Qemu-devel] [PATCH v8 4/5] coroutine: add test-coroutine automated tests Stefan Hajnoczi
2011-08-02 13:43   ` Kevin Wolf
2011-07-26  9:21 ` [Qemu-devel] [PATCH v8 5/5] coroutine: add test-coroutine --benchmark-lifecycle Stefan Hajnoczi
2011-07-26  9:23 ` [Qemu-devel] [PATCH v8 0/5] Coroutines for better asynchronous programming Stefan Hajnoczi
2011-07-27  9:45 ` Aneesh Kumar K.V
2011-07-27 10:03   ` Kevin Wolf [this message]
2011-07-27 11:39     ` Aneesh Kumar K.V
2011-07-27 12:14       ` Kevin Wolf
2011-07-27 11:34   ` Aneesh Kumar K.V
2011-07-29 12:54 ` Stefan Hajnoczi

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