linux-kernel - Re: [dm-devel] dm: Make MIN_IOS, et al, tunable via sysctl.

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Message-ID: <1376934845.24869.43.camel@bobble.lax.corp.google.com>
Date:	Mon, 19 Aug 2013 10:54:05 -0700
From:	Frank Mayhar <fmayhar@...gle.com>
To:	device-mapper development <dm-devel@...hat.com>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: [dm-devel] dm: Make MIN_IOS, et al, tunable via sysctl.

On Mon, 2013-08-19 at 10:00 -0400, Mike Snitzer wrote:
> Performance isn't the concern.  The concern is: does DM allow for
> forward progress if the system's memory is completely exhausted?
> 
> This is why request-based has such an extensive reserve, because it
> needs to account for cloning the largest possible request that comes in
> (with multiple bios).

Thanks for the response.  In our particular case, I/O will be file
system based and over a network, which makes it pretty easy for us to be
sure that large I/Os never happen.  That notwithstanding, however, as
you said it just seems reasonable to make these values configurable.

I'm also looking at making some similar constants in dm-verity and
dm-bufio configurable in the same way and for similar reasons.
-- 
Frank Mayhar
310-460-4042

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