Re: *terrible* speed of savevm/loadvm/delvm

[Avi Kivity <avi@redhat.com>]

Michael Tokarev wrote:
>>> As you see, it writes 2 bytes, llseeks to THE SAME
>>> position, writes next 2 bytes and so on.  This takes
>>> HUGE amount of time, and can be done, in most cases,
>>> in a single write without any seeks.
>>>
>>> Is it just me or are savevm/loadvm/delvm really THAT
>>> broken?
>>>       
>> It's qcow2 that is broken, with the new default cache=writethrough. 
>> Does cache=writeback speed things up?
>>     
>
> Please excuse me for this long delay replying...
> I tried other solutions meanwhile (migrate to exec:), but did not
> succeed there either.
>
> Well.  While with writeback mode, the speed is definitely
> better.  But it is still very very slow - not THAT terrible,
> but it still takes several mins to complete a 512MB VM with
> a single 4Gb qcow2 file.
>   

Any idea what is happening?  Is it disk bound, or cpu bound?

It shouldn't be that slow with writeback.

-- 
error compiling committee.c: too many arguments to function