Re: io_request_lock patch?

Dipankar Sarma
2001-07-11T20:09:05Z

On Wed, Jul 11, 2001 at 09:20:22PM +0200, Jens Axboe wrote:
> True. In theory it would be possible to do request slot stealing from
> idle queues, in fact it's doable without adding any additional overhead
> to struct request. I did discuss this with [someone, forgot who] last
> year, when the per-queue slots where introduced.
>
> I'm not sure I want to do this though. If you have lots of disks, then
> yes there will be some wastage if they are idle. IMO that's ok. What's
> not ok and what I do want to fix is that slower devices get just as many
> slots as a 15K disk for instance. For, say, floppy or CDROM devices we
> really don't need to waste that much RAM. This will change for 2.5, not
> before.

Unless there is some serious evidence substantiating the need for
stealing request slots from other devices to avoid starvation, it
makes sense to avoid it and go for a simpler scheme. I suspect that device
type based slot allocation should just suffice.

Thanks
Dipankar
--
Dipankar Sarma <dipankar@sequent.com> Project: http://lse.sourceforge.net
Linux Technology Center, IBM Software Lab, Bangalore, India.