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Date: Wed, 04 Jan 2012 11:53:21 +0100
From: Peter Lieven <pl@dlh.net>
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Subject: Re: [Qemu-devel] Stalls on Live Migration of VMs with a lot of
	memory
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To: Shu Ming <shuming@linux.vnet.ibm.com>
Cc: qemu-devel@nongnu.org, kvm@vger.kernel.org

On 04.01.2012 02:38, Shu Ming wrote:
> On 2012-1-4 2:04, Peter Lieven wrote:
>> Hi all,
>>
>> is there any known issue when migrating VMs with a lot of (e.g. 32GB) 
>> of memory.
>> It seems that there is some portion in the migration code which takes 
>> too much time when the number
>> of memory pages is large.
>>
>> Symptoms are: Irresponsive VNC connection, VM stalls and also 
>> irresponsive QEMU Monitor (via TCP).
>>
>> The problem seems to be worse on 10G connections between 2 Nodes (i 
>> already tried limiting the
>> bandwidth with the migrate_set_speed command) than on 1G connections.
> Is the migration  accomplished finally? How long will that be?  I did 
> a test on VM with 4G and it took me about two seconds.
it seems that the majority of time (90%) is lost in:

cpu_physical_memory_reset_dirty(current_addr,
                                             current_addr + 
TARGET_PAGE_SIZE,
                                             MIGRATION_DIRTY_FLAG);

anyone any idea, to improve this?