Re: [Qemu-devel] [RFC] block-queue: Delay and batch metadata writes

[Avi Kivity <avi@redhat.com>]

  On 09/20/2010 05:33 PM, Avi Kivity wrote:
>  On 09/20/2010 05:08 PM, Kevin Wolf wrote:
>> >
>> >  Let's expand it a bit more:
>> >
>> >  1. Update refcount table
>> >  2. bdrv_flush
>> >  3. Update L2 entry
>> >  4. Write data to disk
>> >  5. Report write complete
>> >
>> >  I'm struggling to understand how a thread helps out.
>>
>> This sequence becomes:
>>
>> 1. Update refcount table
>> 2. Write data to disk
>> 3. Report write complete
>>
>> And only later:
>>
>> 4. Update L2 entry
>> 5. bdrv_flush (possibly merged with other flushes)
>>
>
> The L2 update needs to happen after we're sure the refcount update is 
> stable, so need a bdrv_flush between them.
>
> Still, the basic idea looks sound.  You can do many refcount updates, 
> flush, many L2 updates, flush.
>


Oh, your original RFC has that flush in place, so all is good.

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