From mboxrd@z Thu Jan  1 00:00:00 1970
From: Joe Thornber <thornber@redhat.com>
Subject: Re: I/O block when removing thin device on the same pool
Date: Fri, 29 Jan 2016 16:05:16 +0000
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To: Dennis Yang <dennisyang@qnap.com>
Cc: device-mapper development <dm-devel@redhat.com>
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On Fri, Jan 29, 2016 at 07:01:44PM +0800, Dennis Yang wrote:
> I had tried to define MAX_DECS as 1, 16, and 8192, and here is the
> throughput I got.
> When #define MAX_DECS 1, throughput drops from 3.2GB/s to around 800 ~ 950
> MB/s.
> When #define MAX_DECS 16, throughput drops from 3.2GB/s to around 150 ~ 400
> MB/s
> When #define MAX_DECS 8192, the I/O blocks until deletion is done.
> 
> These throughput is gathered by writing to a newly created thin device
> which means lots of provisioning take place. So it seems that the more fine
> grained lock we use here results in the higher throughput. Is there any
> concern if I set MAX_DECS to 1 for production?

Does the time taken to remove the thin device change as you drop it to one?

- Joe