Date: Thu, 21 Jun 2007 16:08:11 -0700 (PDT)
From: Linus Torvalds <torvalds@linux-foundation.org>
To: Matt Mackall <mpm@selenic.com>
cc: Jens Axboe <jens.axboe@oracle.com>, Peter Zijlstra <peterz@infradead.org>,
       Andrew Morton <akpm@linux-foundation.org>, davej@redhat.com,
       tim.c.chen@linux.intel.com, linux-kernel@vger.kernel.org
Subject: Re: Change in default vm_dirty_ratio
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On Thu, 21 Jun 2007, Matt Mackall wrote:
> 
> Perhaps we want to throw some sliding window algorithms at it. We can
> bound requests and total I/O and if requests get retired too slowly we
> can shrink the windows. Alternately, we can grow the window if we're
> retiring things within our desired timeframe.

I suspect that would tend to be a good way to go. But it almost certainly 
has to be per-device, which implies that somebody would have to do some 
major coding/testing on this..

The vm_dirty_ratio thing is a global value, and I think we need that 
regardless (for the independent issue of memory deadlocks etc), but if we 
*additionally* had a per-device throttle that was based on some kind of 
adaptive thing, we could probably raise the global (hard) vm_dirty_ratio a 
lot.

		Linus
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