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Date: Fri, 23 Apr 2010 16:14:42 +0300
From: Avi Kivity <avi@redhat.com>
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Subject: [Qemu-devel] Re: [RFC PATCH 04/20] Make QEMUFile buf expandable,
 and introduce qemu_realloc_buffer() and qemu_clear_buffer().
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To: Yoshiaki Tamura <tamura.yoshiaki@lab.ntt.co.jp>
Cc: aliguori@us.ibm.com, kvm@vger.kernel.org, ohmura.kei@lab.ntt.co.jp, mtosatti@redhat.com, qemu-devel@nongnu.org, yoshikawa.takuya@oss.ntt.co.jp

On 04/23/2010 12:59 PM, Yoshiaki Tamura wrote:
> 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.

How large can it grow?

What's wrong with applying it (perhaps partially) to the guest state?  
The next state transfer will overwrite it completely, no?

-- 
Do not meddle in the internals of kernels, for they are subtle and quick to panic.