Andrea Arcangeli's per-task-predictive-write-throttling
Posted Sep 29, 2005 10:41 UTC (Thu) by nix
In reply to: Andrea Arcangeli's per-task-predictive-write-throttling
Parent article: Swap prefetching
It's a good idea, that patch, definitely. For a pathological example, my backup process involves multi-hundred-Mb copies to a packet-written CD-RW. This generally floods almost all of memory with dirtied pages and then flushes them to this rather slow device, making the machine slow and swappy for a quarter-hour or so until the flush is done: with predictive write throttling, I'd expect to see a steady trickle instead, at something close to it.
(Even the current behaviour is much better than Linux-2.4, where the fact that block devices didn't have their own queues led to the entirety of X and everything I was doing freezing solid within a second or two of the flush beginning; the system was more swappy than normal because memory was filled with all those dirty pages, and a tiny and otherwise-unnoticeable bit of swapping or paging was stuck behind the vast heap of stuff destined for the CD-RW.)
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