Messages in this thread | | | Subject | Re: [RFC][PATCH] create workqueue threads only when needed | From | Benjamin Herrenschmidt <> | Date | Mon, 02 Feb 2009 20:05:28 +1100 |
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On Mon, 2009-02-02 at 09:42 +0100, Stefan Richter wrote:
> > > > IE. It will be pretty responsive -in general- but can suffer form > > horrible latencies every now and then. > > Actually it /should/ be the other way around: > > The shared workqueue should only be used for work that sleeps only > briefly (perhaps with the exception of very unlikely longer sleeps e.g. > for allocations that cause paging).
I agree, I'm just stating the current situation :-) Hopefully something like async funcs / slow work / whatever will take over the case of stuff that wants to be around for longer. I haven't had a chance to look at the async funcs yet, sounds like they may do the job tho in which case I'll look at converting a driver or two to use them.
> Work which /may/ sleep longer, for example performs SCSI transactions, > needs to go into a private workqueue or other kind of context.
Well, it's a bit silly to allocate a private workqueue with all it's associated per CPU kernel threads for something as rare as resetting your eth NIC ... or even SCSI error handling in fact.
> OTOH you are right too; work which must not be deferred too long by work > from another uncooperative/ unfair subsystem is probably also better off > in an own workqueue...
I suspect the main reason for dedicated work queues is that, plus the per-CPU affinity.
Cheers, Ben.
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