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Date: Mon, 08 Sep 2008 16:04:55 +0200 From: Christer Weinigel <christer@...nigel.se> To: Ben Dooks <ben-linux@...ff.org> CC: linux-kernel@...r.kernel.org Subject: Re: [patch 2/3] s3cmci - call pio_tasklet from IRQ Ben Dooks wrote: > On Mon, Sep 08, 2008 at 02:48:50PM +0200, Christer Weinigel wrote: >> Scheduling a tasklet to perform the pio transfer introduces a bit of >> extra processing, just call pio_tasklet directly from the interrupt >> instead. Writing up to 64 bytes to a FIFO is probably uses less CPU >> than scheduling a tasklet anyway. > > Hmm, i'd be interested to find out how long these are taking... I might > try and rig up something to test the time being taken via an SMDK. > > If the fifo read/writes are taking significant amounts of time, then the > pio tasklet will at least improve the interrupt latencies invloved, as > iirc we're currently running the main irq handler in IRQ_DISABLED mode > to stop any problems with re-enternancy.... I'll check this and see what > is going on. It should be possible to set a flag and then call the pio_task after the spin_unlock_irqrestore instead. I didn't want to do that to change as little of the logic as possible, but it's probably better to do that. I'm also thinking of changing send_request to do a busy wait for commands without data, that will probably need a bit larger changes. /Christer -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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