Subject: Re: Too many I/O controller patches
From: Dave Hansen <dave@linux.vnet.ibm.com>
To: righi.andrea@gmail.com
Cc: Satoshi UCHIDA <s-uchida@ap.jp.nec.com>, xen-devel@lists.xensource.com,
       containers@lists.linux-foundation.org, linux-kernel@vger.kernel.org,
       vtaras@openvz.org, dm-devel@redhat.com, agk@sourceware.org,
       virtualization@lists.linux-foundation.org, ngupta@google.com
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Date: Tue, 05 Aug 2008 09:20:18 -0700
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On Tue, 2008-08-05 at 11:28 +0200, Andrea Righi wrote:
> > Buffered write I/O is also related with cache system.
> > We must consider this problem as I/O control.
> 
> Agree. At least, maybe we should consider if an IO controller could be
> a valid solution also for these problems.

Isn't this one of the core points that we keep going back and forth
over?  ﻿It seems like people are arguing in circles over this:

Do we:
	1. control potential memory usage by throttling I/O
or
	2. Throttle I/O when memory is full

I might lean toward (1) if we didn't already have a memory controller.
But, we have one, and it works.  Also, we *already* do (2) in the
kernel, so it would seem to graft well onto existing mechanisms that we
have.

I/O controllers should not worry about memory.  They're going to have a
hard enough time getting the I/O part right. :)

﻿Or, am I over-simplifying this?

-- Dave


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