From mboxrd@z Thu Jan  1 00:00:00 1970
From: Yoshiaki Tamura <tamura.yoshiaki@lab.ntt.co.jp>
Subject: Re: [RFC PATCH 04/20] Make QEMUFile buf expandable, and introduce
 qemu_realloc_buffer() and qemu_clear_buffer().
Date: Fri, 23 Apr 2010 18:59:40 +0900
Message-ID: <4BD16F8C.5010007@lab.ntt.co.jp>
References: <1271829445-5328-1-git-send-email-tamura.yoshiaki@lab.ntt.co.jp> <1271829445-5328-5-git-send-email-tamura.yoshiaki@lab.ntt.co.jp> <4BD16E30.5080502@redhat.com>
Mime-Version: 1.0
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 7bit
Cc: kvm@vger.kernel.org, qemu-devel@nongnu.org, aliguori@us.ibm.com,
	mtosatti@redhat.com, ohmura.kei@lab.ntt.co.jp,
	yoshikawa.takuya@oss.ntt.co.jp
To: Avi Kivity <avi@redhat.com>
Return-path: <kvm-owner@vger.kernel.org>
Received: from tama50.ecl.ntt.co.jp ([129.60.39.147]:35969 "EHLO
	tama50.ecl.ntt.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
	with ESMTP id S1755958Ab0DWKAF (ORCPT <rfc822;kvm@vger.kernel.org>);
	Fri, 23 Apr 2010 06:00:05 -0400
In-Reply-To: <4BD16E30.5080502@redhat.com>
Sender: kvm-owner@vger.kernel.org
List-ID: <kvm.vger.kernel.org>

Avi Kivity wrote:
> On 04/21/2010 08:57 AM, Yoshiaki Tamura wrote:
>> Currently buf size is fixed at 32KB. It would be useful if it could
>> be flexible.
>>
>
> Why is this needed? The real buffering is in the kernel anyways; this is
> only used to reduce the number of write() syscalls.

This was introduced to buffer the transfered guests image transaction ally on 
the receiver side.  The sender doesn't use it.
In case of intermediate state, we just discard this buffer.