Re: [PATCH] pnfsblock: Lookup list entry of layouts and tags in reverse order

[Boaz Harrosh <bharrosh@panasas.com>]

On 05/17/2010 04:53 PM, J. Bruce Fields wrote:
> On Wed, May 12, 2010 at 04:28:12PM -0400, bfields wrote:
>> On Wed, May 12, 2010 at 09:46:43AM +0300, Benny Halevy wrote:
>>> On May. 10, 2010, 6:36 +0300, Zhang Jingwang <zhangjingwang-U4AKAne5IzAR5TUyvShJeg@public.gmane.org> wrote:
>>>> Optimize for sequencial write. Layout infos and tags are organized by
>>>> file offset. When appending data to a file whole list will be examined,
>>>> which introduce notable performance decrease.
>>>
>>> Looks good to me.
>>>
>>> Fred, can you please double check?
>>
>> I don't know if Fred's still up for reviewing block stuff?
>>
>> I've been trying to keep up with at least some minimal testing, but not
>> as well as I'd like.
>>
>> The one thing I've noticed is that the connectathon general test has
>> started failing right at the start with an IO error.  The last good
>> version I tested was b5c09c21, which was based on 33-rc6.  The earliest
>> bad version I tested was 419312ada, based on 34-rc2.  A quick look at
>> network traces from the two traces didn't turn up anything obvious.  I
>> haven't had the chance yet to look closer.
> 
> As of the latest (6666f47d), in my tests the client is falling back on
> IO to the MDS and doing no block IO at all.  b5c09c21 still works, so
> the problem isn't due to a change in the server I'm testing against.  I
> haven't investigated any more closely.
> 

You might be hitting the .commit bug, no? Still no fix. I'm using a work
around for objects. I'm not sure how it affects blocks. I think you should
see that the very first IO goes through layout driver then the IO is redone
through MDS, for each node. Even though write/read returned success because
commit returns NOT_ATTEMPTED. But I might be totally off.

Boaz
> --b.
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