From mboxrd@z Thu Jan  1 00:00:00 1970
Received: from eggs.gnu.org ([140.186.70.92]:34384)
	by lists.gnu.org with esmtp (Exim 4.71)
	(envelope-from <anthony@codemonkey.ws>) id 1QjA9Q-0006EG-Jt
	for qemu-devel@nongnu.org; Tue, 19 Jul 2011 09:15:57 -0400
Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71)
	(envelope-from <anthony@codemonkey.ws>) id 1QjA9O-0007yH-NA
	for qemu-devel@nongnu.org; Tue, 19 Jul 2011 09:15:52 -0400
Received: from mail-gw0-f45.google.com ([74.125.83.45]:56037)
	by eggs.gnu.org with esmtp (Exim 4.71)
	(envelope-from <anthony@codemonkey.ws>) id 1QjA9O-0007yA-7G
	for qemu-devel@nongnu.org; Tue, 19 Jul 2011 09:15:50 -0400
Received: by gwb19 with SMTP id 19so1971542gwb.4
	for <qemu-devel@nongnu.org>; Tue, 19 Jul 2011 06:15:49 -0700 (PDT)
Message-ID: <4E258383.6040609@codemonkey.ws>
Date: Tue, 19 Jul 2011 08:15:47 -0500
From: Anthony Liguori <anthony@codemonkey.ws>
MIME-Version: 1.0
References: <CAHt6W4fMhr0voMsiJ-1-PgE2WKh0F+-Oft_Byh-8ffh3JgKeMg@mail.gmail.com>
	<4E255823.8080502@redhat.com>
In-Reply-To: <4E255823.8080502@redhat.com>
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 7bit
Subject: Re: [Qemu-devel] coroutines and block I/O considerations
List-Id: <qemu-devel.nongnu.org>
List-Unsubscribe: <https://lists.nongnu.org/mailman/options/qemu-devel>,
	<mailto:qemu-devel-request@nongnu.org?subject=unsubscribe>
List-Archive: <http://lists.nongnu.org/archive/html/qemu-devel>
List-Post: <mailto:qemu-devel@nongnu.org>
List-Help: <mailto:qemu-devel-request@nongnu.org?subject=help>
List-Subscribe: <https://lists.nongnu.org/mailman/listinfo/qemu-devel>,
	<mailto:qemu-devel-request@nongnu.org?subject=subscribe>
To: Kevin Wolf <kwolf@redhat.com>
Cc: Frediano Ziglio <freddy77@gmail.com>, qemu-devel@nongnu.org

On 07/19/2011 05:10 AM, Kevin Wolf wrote:
> Am 19.07.2011 10:06, schrieb Frediano Ziglio:
> They are still all running in the same thread.
>
>> 2- memory considerations on coroutines. Beside coroutines allow more
>> readable code I wonder if somebody considered memory. For every
>> coroutines a different stack has to be allocated. For instance
>> ucontext and win32 implementation use 4mb. Assuming 128 concurrent AIO
>> this require about 512mb of ram (mostly only committed but not used
>> and coroutines are reused).
>
> 128 concurrent requests is a lot. And even then, it's only virtual
> memory. I doubt that we're actually using much more than we do in the
> old code with the AIOCBs (which will disappear and become local
> variables when we complete the conversion).

A 4mb stack is probably overkill anyway.  It's easiest to just start 
with a large stack and then once all of the functionality is worked out, 
optimize to a smaller stack.

The same problem exists with using threads FWIW since the default thread 
stack is usually quite large.

Regards,

Anthony Liguori