Re: [Kiobuf-io-devel] RFC: Kernel mechanism: Compound event wait

From: Jens Axboe (
Date: Tue Feb 06 2001 - 15:07:04 EST

On Tue, Feb 06 2001, Ingo Molnar wrote:
> > This small correction is the crux of the problem: if it blocks, it
> > takes away from the ability of the process to continue doing useful
> > work. If it returns -EAGAIN, then that's okay, the io will be
> > resubmitted later when other disk io has completed. But, it should be
> > possible to continue servicing network requests or user io while disk
> > io is underway.
> typical blocking point is waiting for page completion, not
> __wait_request(). But, this is really not an issue, NR_REQUESTS can be
> increased anytime. If NR_REQUESTS is large enough then think of it as the
> 'absolute upper limit of doing IO', and think of the blocking as 'the
> kernel pulling the brakes'.

Not just __get_request_wait, but also the limit on max locked buffers
in ll_rw_block. Serves the same purpose though, brake effect.

Jens Axboe

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