Re: [PATCH 0/3] flush delalloc by multi-task

[Miao Xie <miaox@cn.fujitsu.com>]

On Fri, 26 Oct 2012 10:05:55 +0800, Liu Bo wrote:
> On 10/26/2012 09:56 AM, Miao Xie wrote:
>>> I can see the potential improvements brought by flushing inodes this way.
>>>>
>>>> But I don't think it makes much sense by making waiting process multi-task,
>>>> since even we spread wait order extents into different cpus, they just occpied
>>>> the cpu and went on waiting and scheduled then, I mean, the bottleneck is on
>>>> what we're waiting for.
>> Thanks for your comment, I think only btrfs_run_ordered_operations(root, 0) needn't
>> wait for the works, the others must wait.
>>
>> The first reason is to avoid changing the semantic of those tree function. The second
>> reason is we have to wait for the completion of all works, if not, the file data in
>> snapshots may be different with the source suvolumes because the flush may not end
>> before the snapshot creation.
>>
> 
> Yes, it's right that they must wait for all workers to finish.
> 
> But I don't mean that(sorry for my confusing words).
> 
> IMO we don't need to let *btrfs_wait_ordered_extents()* run as multi-task.

It also need to be done by multi-task because btrfs_wait_ordered_extents() doesn't imply
that all the dirty pages in the ordered extent have been written into the disk, that is
it also need do lots of things before waiting for the event - BTRFS_ORDERED_COMPLETE, so
the multi-task process is useful, I think.

Anyway, we need test to validate it.

Thanks
Miao

> 
> thanks,
> liubo
> 
> 
> 
>