Messages in this thread | | | Date | Fri, 27 Feb 2004 11:06:17 +0100 | From | Helge Hafting <> | Subject | Re: [RFC][PATCH] O(1) Entitlement Based Scheduler |
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Peter Williams wrote: > Timothy Miller wrote: > >> How about this: >> >> The kernel tracks CPU usage, time slice expiration, and numerous other >> statistics, and exports them to userspace through /proc or somesuch. >> Then a user-space daemon adjusts priority. > > > Yes, the right statistics could allow these processes to be identified > reasonably accurately. The programs in question would have the > following characteristics: > > 1. low CPU usage rate, and > 2. a very regular pattern of use i.e. the size of each CPU bursts would > be approximately constant as would the size of the intervals between > each burst.
There is no need for the regularity. When I use a word processor, I use it very irregularly. Sometimes I type text, and wants each letter typed to appear instantly. This fits well with "low cpu usage" and sudden short bursts. There may be lots of long delays though while I think about stuff to write. So the intervals are irregular, I still believe I should get the boosts as long as the bursts are small. Doing something big (such as invoking latex on a big document) is cpu-heavy, but then it is ok not to get the boost. Current schedulers based on io-waiting gets this right already. > > The appropriate statistic to identify the second of these would be > variance or (equivalently but more expensively) standard deviation. > Whether this problem is bad/important enough to warrant the extra > overhead of gathering these statistics is a moot point. We had to > generate very high system loads on a single CPU system in order to cause > one or two skips in xmms over a period of a couple of minutes.
Well, perhaps you could give a slightly bigge boost to a very regular thing like xmms. But even that might have some snags, the load might change a lot when doing midi in software, depending on how many instruments are active simultaneously. There goes the constant-size bursts.
Helge Hafting
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