From: Rik v. R. <ri...@co...> - 2001-02-11 19:52:28
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On Fri, 9 Feb 2001, John Hawkes wrote: > Is there anyone in the Linux Community who believes that > the current scheduler is perfect? Unlikely, even on dual-CPU machines with large caches (ie. Xeon systems) it does something very bad... Suppose you have 2 CPU's and 3 CPU-eating tasks (eg. 2 threads of a long-running job and one compiler .. fairly common stuff). Now one of the CPU-bound tasks is halfway its timeslice and gets interrupted by eg. /usr/bin/vi. After vi gives up the CPU, the scheduler will select *another* task to run on the CPU, instead of switching back to the previous CPU-intensive task... Also, recalculating the priority of *every* task in the system at recalculation time has the possibility of blowing away a too large portion of the cache if you're running with huge amounts of processes (and some nice ping-pong effects if you have multiple CPUs recalculating at once, as can happen when you have a bunch of nice +19 processes). regards, Rik -- Linux MM bugzilla: http://linux-mm.org/bugzilla.shtml Virtual memory is like a game you can't win; However, without VM there's truly nothing to lose... http://www.surriel.com/ http://www.conectiva.com/ http://distro.conectiva.com/ |