Re: Change in default vm_dirty_ratio



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.

And with hot-pluggable devices (which is where most of the throughput
problems tend to be!), the "one-off" thing is not a "just after reboot"
kind of situation.

So you'd have to be pretty smart about it.

Linus
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