Date:	Fri, 3 Feb 2012 17:00:37 +0800
From:	Yongqiang Yang <xiaoqiangnk@...il.com>
To:	Allison Henderson <achender@...ux.vnet.ibm.com>
Cc:	Tao Ma <tm@....ma>,
	Ext4 Developers List <linux-ext4@...r.kernel.org>,
	"Ted Ts'o" <tytso@....edu>, Andreas Dilger <adilger@...ger.ca>
Subject: Re: Delayed Extent Tree and Extent Lock Tree

On Thu, Feb 2, 2012 at 6:04 AM, Allison Henderson
<achender@...ux.vnet.ibm.com> wrote:
> On 02/01/2012 12:26 AM, Tao Ma wrote:
>>
>> Hi Allison,
>> On 02/01/2012 06:33 AM, Allison Henderson wrote:
>>>
>>> Hi Yongqiang,
>>>
>>> I've have been working on an extent lock implementation that uses an
>>> rbtree to keep track of locked extents, and I think I will probably end
>>> up with a something similar to the tree that you've already set up for
>>> delayed extents.  So I wanted to send a note out to see what folks would
>>> think about the idea of merging the two solutions.
>>>
>>> If we did this, the tree would get a little more complex in that it
>>> would have to keep track of more than just delayed extents. It would
>>> have to keep track of all extents and the processes that are waiting on
>>> them.  So I guess it would kind of turn into an extent status tree.  I
>>> also realize that some folks wanted to see range locks go into /lib as
>>> general purpose code so that other filesystems or kernel code could use
>>> it too, but the advantage to this approach would be one less tree for
>>> ext4 to keep track of.  Any thoughts?
>>
>> We (Taobao) are very interested in this stuff and it should benefit
>> several of our workload(It is on our todo list for a long time). I guess
>> Yongqiang's solution is a little bit limited to the only delayed extent
>> case, and your new solution at least has 2 more benefits:
>> 1. improve the direct i/o read/write
>> 2. speed up the extent search since now we only cache one in
>> ei_cached_extent.
>>
>> So please go ahead with your new solution. btw, do you have any timeline
>> for it? We are glad to provide any help if needed.
>>
>> Thanks
>> Tao
>>
>
> Thx all for the feed back, it sounds like there will be a lot of benefits to
> extending Yongqiang's delayed extent tree, so I will work on a solution
> based on that patch set.  Unfortunately though, I cannot give a time frame
> for this work item at the moment.  There are currently some other business
> needs that may take priority over this one, and until those have been
> decided, I cannot make any promises at this point in time.  But I will work
> as quickly as I can with it since it is currently on my plate, and I will
> keep folks updated.  At the moment, feed back and guidance is most helpful
> to me.  Also, since the delayed extent solution is now a dependency for my
> solution, anything to help get that reviewed and merged would help me too.
>  Yongqiang, does the set still need review?  I think I recall Ted saying it
It passed xfstests last year and I think you can go ahead on the set.
 It seems that your changes are a lot, so maybe we can merge the whole
set until your work is done.  At least, your work and the merging work
can be undertaken concurrently.

If you need any help,  I am available.

Yongqiang.
> was still on his list of things to look at.  Im sure I will give it some
> good exercise here too.  Thx all for your help!  :)
>
> Allison Henderson
>



-- 
Best Wishes
Yongqiang Yang
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