Re: Change in default vm_dirty_ratio

[Arjan van de Ven <arjan@infradead.org>]

On Wed, 2007-06-20 at 10:17 -0700, Linus Torvalds wrote:
> 
> On Wed, 20 Jun 2007, Peter Zijlstra wrote:
> > 
> > Building on the per BDI patches, how about integrating feedback from the
> > full-ness of device queues. That is, when we are happily doing IO and we
> > cannot possibly saturate the active devices (as measured by their queue
> > never reaching 75%?) then we can safely increase the total dirty limit.
> 
> The really annoying things are the one-off things. You've been happily 
> working for a while (never even being _close_ to saturatign any IO 
> queues), and then you untar a large tree.
> 
> If the kernel now let's you dirty lots of memory, you'll have a very 
> unpleasant experience.


maybe that needs to be fixed? If you stopped dirtying after the initial
bump.. is there a reason for the kernel to dump all that data to the
disk in such a way that it disturbs interactive users?

so the question maybe is.. is the vm tunable the cause or the symptom of
the bad experience?