Messages in this thread | | | Date | Sat, 05 Oct 2002 19:15:49 -0700 | From | Andrew Morton <> | Subject | Re: The reason to call it 3.0 is the desktop (was Re: [OT] 2.6 not 3.0 - (NUMA)) |
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Rob Landley wrote: > > And the work that matters for the desktop is LATENCY work.
100% true.
You should resist any confusion between IO latency and CPU scheduling latency. They really are worlds apart.
In a stock 2.4 kernel it is hugely rare for the kernel to stall a ready-to-run task for longer than a monitor refresh interval, so I continue to disbelieve any claims that the low-latency and preemptivity patches make any difference in desktop use.
(And 2.5 improves on this a _lot_. The now-departed buffer LRU and truncate list walks were the main culprits)
Any attempt to link IO priority with nice is probably doomed to confused failure. It should be a clearly separated concept. There are priority inversions everywhere, too.
I disagree with you on the new CPU scheduler. In my experience it is significantly worse than the old one - a `make -j3' is still sending interactive applications on extended lunch breaks. Not that I have tried to tune this away.
Deadline scheduler is critical. As is a correct setting for /proc/sys/vm/dirty_async_ratio and the soon-to-be-born /proc/sys/vm/swappiness. These will boot up with sane values, as much as is humanly possible.
It's not all kernel though. Application (KDE) startup is *slow*, even when zero I/O is performed. Presumably because of the vtable dynamic linking thing. I'm not sure how the prelinking work is getting along, but the initial figures I saw on that indicated that the benefit may not be sufficient. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.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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