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

From: Joe Thornber
Date: Wed Dec 10 2014 - 08:14:39 EST

On Wed, Dec 10, 2014 at 09:59:12PM +0900, Akira Hayakawa wrote:
> 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?

Yes, writing across the whole device using 'dd'.

These are the tests:

dmtest list --suite writeboost -n /wipe_device/

> 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).

So you copy the bio payload to a different block of ram and then
complete the bio? Or does the rambuf refer to the bio payload

> 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)...

I generally find it quicker to investigate problems on the machine
that are actually exhibiting the problem ;) Seriously though, you're
asking us to send this upstream; it needs to work on consumer level

I've got a big machine with Fusion IO storage that I can run the same
tests on later.

- Joe
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