linux-kernel - Re: [dm-devel] [PATCH] staging: writeboost: Add dm-writeboost

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Date:	Wed, 10 Dec 2014 21:59:12 +0900
From:	Akira Hayakawa <ruby.wktk@...il.com>
To:	ejt@...hat.com
CC:	dm-devel@...hat.com, gregkh@...uxfoundation.org,
	snitzer@...hat.com, agk@...hat.com, linux-kernel@...r.kernel.org
Subject: Re: [dm-devel] [PATCH] staging: writeboost: Add dm-writeboost

Joe,

I appreciate your continuous work.

Is that read or write?
The difference between Type 0 and 1 should only show up in write path.
So is it write test?

And what is the unit of each result?

> So maybe it's just volume of IO that's causing the problem?  What's
> the difference between Type 0 and Type 1?  In the code I notice you
> have 'rambuf' structures, are you caching IO in memory?
"rambuf" is a temporary space that every write data comes in.
127*4KB data are once stored there and 4KB metadata section are added
then it becomes a log and flushed to the cache device sequentially (512KB each).

By the way,
I think more clearer discussion can be done if tests are done on physical machines
to isolate things relevant to VM. I will also add these tests to dmts later and
run on my machine.
But, it will be much better if we have good server with RAID-ed backing store
and the newest SSD (How would it be if it's PCI-e SSD)... 

- Akira

On 12/10/14 9:33 PM, Joe Thornber wrote:
> On Wed, Dec 10, 2014 at 08:00:13PM +0900, Akira Hayakawa wrote:
>> Hi, Joe
>>
>> Thanks for continuous evaluation.
> 
> Some more details:
> 
> dd, with block size 512b
> ------------------------
> 
> raw spindle      : 143
> writeboost Type 0: 137
> writeboost Type 1: 130
> 
> dd, with block size 4k
> ----------------------
> 
> raw spindle      : 31
> writeboost Type 0: 29
> writeboost Type 1: 81
> 
> 
> dd, with block size 64m
> -----------------------
> 
> raw spindle      : 8.9
> writeboost Type 0: 32
> writeboost Type 1: 72
> 
> 
> 
> So maybe it's just volume of IO that's causing the problem?  What's
> the difference between Type 0 and Type 1?  In the code I notice you
> have 'rambuf' structures, are you caching IO in memory?
> 

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