Subject: Re: Change in default vm_dirty_ratio
From: Peter Zijlstra <peterz@infradead.org>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Matt Mackall <mpm@selenic.com>, Jens Axboe <jens.axboe@oracle.com>,
       Andrew Morton <akpm@linux-foundation.org>, davej@redhat.com,
       tim.c.chen@linux.intel.com, linux-kernel@vger.kernel.org
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Date: Sat, 23 Jun 2007 20:23:50 +0200
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On Thu, 2007-06-21 at 16:08 -0700, Linus Torvalds wrote:
> 
> 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.

I just did quite a bit of that:

  http://lkml.org/lkml/2007/6/14/437

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