Messages in this thread | | | From | (Zygo Blaxell) | Subject | Re: AMIGA will use Linux, but Linux has several "multimedia-deficiencies" | Date | 12 Jul 1999 14:57:10 -0400 |
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In article <99071018080700.00820@linuxhost.localdomain>, Benno Senoner <sbenno@gardena.net> wrote: >I was shocked when disabling DMA on my HD, my realtime process was >not rescheduled for *4000ms* = 4sec ! >(a 100m sprinter is able to run 35m in the same time :-) )
That's nothing. I once got an upper bound of 35000ms (that's more than enough time for *me* to finish a 100m sprint ;-) out of a PII-300 with a 7200RPM IDE UDMA drive doing video capture. Delays of 5-6 seconds were more common. SCSI would give me delays of 3-4 seconds, which is better, but not quite good enough to be useful (I had enough RAM to cope with ~3300ms of I/O latency at the time).
The weird thing that I've noticed is that for multimedia work Pentium-class machines running Linux 2.0 have better (or at least less bursty) scheduling than PIII-450's running Linux 2.2. Sure, the scheduler would deadlock from time to time in 2.0, but at least while the machine was running, it _worked_, damnit!
I dispute the assertion that this is due to optimization away from realtime scheduling toward time sharing, because it's simply bad time sharing as well. The CPU is not executing some other process or reorganizing the buffer cache or blocking on disk I/O; it's simply idle, while there are runnable tasks waiting for a CPU.
-- Zygo Blaxell, Linux Engineer, Corel Corporation. zygob@corel.ca (work) or zblaxell@furryterror.org (play). Opinions above are my own, not Corel's. Size of 'diff -Nurw [...] winehq corel' as of Thu Jun 3 13:14:00 EDT 1999 Lines/files: In 20094 / 98, Out 17319 / 152, Both 12093 / 142
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