Re: [RFC PATCH] Decrease Metadata Fragment By Using a Caterpillar Band Method(intro modified)

["WeiFeng Liu" <weifeng.liu@hushmail.com>]

On Sunday, May 27, 2012 at 5:44 PM, Liu Bo <liubo2009@cn.fujitsu.com> wrote:
>

>Hi,
>
>Thanks for working on this.
>
>Do you have any performance number?
>
>The idea is an interesting one, but I have no idea if it really 
>works, because blocks are
>still fragments:
>
>|   16k     |     16k   |    16k    |
>|----|A|----|----|B|----|----|C|----|
>
>
>Or am I missing something?
>
>thanks,
>liubo
>

Hi, Liu Bo

I noticed your graphic and what you said, "still fragments" 
thanks you.

According my patch's logic, any COWs for tree block A will be limited in it's
16k caterpillar band in the example, at least theoretically, and so tree block
B, like the following:

|<-- A circulated in 16k -->|   |<-- B circulated in 16k -->|
|--a-->|--b-->|--c-->|--d-->|   |--a-->|--b-->|--c-->|--d-->|
|                           |   |                           |
|-------------<-------------|   |-------------<-------------|

	Liu Bo, are the fragments you mentioned referenced to the ones in a caterpillar
or ones out of a caterpillar? if they are in a caterpillar, nothing would be
worried, because they are supposed to stay there forever, and that efficiency
is just what I want. 

	To a certain degree, using a caterpillar for a tree block is somewhat 
similar with the way superblock runs, a superblock circularly updated in a 
cluster of DISCONTINUOUS blocks within a large range, and I use a caterpillar
band to force a tree block updated circularly in a continuous blocks within a
compact area.

Sorry, I haven't yet take performance test for my patch now, a bit more times
are still needed for me to check the possible bugs in code's routes before
tests, and any comments are welcome.

Thanks all you.

WeiFeng Liu
523f28f9b3d9c710cacc31dbba644efb1678cf62