Re: throttling dirtiers

[Benjamin LaHaise <bcrl@redhat.com>]

On Wed, Jul 31, 2002 at 01:06:12PM -0700, William Lee Irwin III wrote:
> I'm not a fan of this kind of global decision. For example, I/O devices
> may be fast enough and memory small enough to dump all memory in < 1s,
> in which case dirtying most or all of memory is okay from a latency
> standpoint, or it may take hours to finish dumping out 40% of memory,
> in which case it should be far more eager about writeback.

Why?  Filling the entire ram with dirty pages is okay, and in fact you 
want to support that behaviour for apps that "just fit" (think big 
scientific apps).  The only interesting point is that when you hit the 
limit of available memory, the system needs to block on *any* io 
completing and resulting in clean memory (which is reasonably low 
latency), not a specific io which may have very high latency.

		-ben
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