Re: [alsa-devel] Re: [patch] `cp /dev/zero /tmp' (patch against 2.2.9)

Benno Senoner (sbenno@gardena.net)
Wed, 16 Jun 1999 20:28:47 +0200


> Unfortunately it does completely the wrong thing if you have more than
> one disk: it stalls all writes on all disks as soon as any one disk goes
> into wait-on-read. That's not good. Not good at all.
>
> This is precisely the problem with optimising for one micro-benchmark.
>
> We really do need per-block-device IO scheduling, in some form or
> another, to fix this once and for all. We already have the per-device
> CURRENT queues, so some of the necessary infrastructure is in place
> today (and the current mechanism does support devices specifying their
> own queues to let them share queues sensibly).
>
> --Stephen

Stephen,
do you think that a per-block-device IO scheduling will cure the
70-150ms stall of audio playing applications during heavy disk I/O ?

Just for curiousity , will it take much time to implement the
per-device scheduling on Linux ?
will future 2.3.x series have these features ?

Do you think that we could archieve similar low scheduling latencies
as with microkerneled OSes (like BeOS) , or is this a design implementation
of monolithic kernels ?
>From what I heard IRIX is able to handle RT scheuled processes
with deadlines of 1ms even under high load, and IRIX is monolithic.
(correct me if I'm wrong)

Therefore a 15-20ms max scheduling deadline
(on modern PC hardware) should be realistic under Linux.

regards,
Benno.

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