On Sat, Oct 03 2009, Mike Galbraith wrote: > On Sat, 2009-10-03 at 09:24 +0200, Jens Axboe wrote: > > > After shutting down the computer yesterday, I was thinking a bit about > > this issue and how to solve it without incurring too much delay. If we > > add a stricter control of the depth, that may help. So instead of > > allowing up to max_quantum (or larger) depths, only allow gradual build > > up of that the farther we get away from a dispatch from the sync IO > > queues. For example, when switching to an async or seeky sync queue, > > initially allow just 1 in flight. For the next round, if there still > > hasn't been sync activity, allow 2, then 4, etc. If we see sync IO queue > > again, immediately drop to 1. > > > > It could tie in with (or partly replace) the overload feature. The key > > to good latency and decent throughput is knowing when to allow queue > > build up and when not to. > > Hm. Starting at 1 sounds a bit thin (like IDLE), multiple iterations to > build/unleash any sizable IO, but that's just my gut talking. Not sure, will need some testing of course. But it'll build up quickly. -- Jens Axboe -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
