Messages in this thread | | | Date | Wed, 29 Mar 2000 09:31:27 -0700 | From | yodaiken@fsmlabs ... | Subject | Re: [patch] preemptive kernel, preemptive-2.3.52-A7 |
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On Wed, Mar 29, 2000 at 12:07:29PM +0200, Ingo Molnar wrote: > > Victor, the lowlatency patch takes care of all code paths that keep the > CPU for more than ~200-400 usecs without looking at current->need_resched. > While such work (the lowlatency patch) is always inexact because > source-level latency validation of 2 million lines of code is pretty much > impossible (although work on that front is advancing and some of the most > obvious abusers were fixed in 2.3), 'practical measurements' (Senno's > measurement tool + a loaded system) show good results. RTLinux is so > lowlevel (because it provides it's own small & atomic API orothogonal to > the base kernel) that source-level validation is much easier.
My reservation about the low-latency patch is in the method of fixing these long sections. If inode reclaim is too slow, we can either introduce more checks for needs resched or try to find a smart data structure/algorithm that does the work faster. If read/write is too slow, figuring out some way to force it into mmap or do something else smart is an alternative to checking needs resched.
I wish that one of the vendors would put together a big test system to evaluate patches on a range of systems and conditions.
-- --------------------------------------------------------- Victor Yodaiken FSMLabs: www.fsmlabs.com www.rtlinux.com FSMLabs is a servicemark and a service of VJY Associates L.L.C, New Mexico.
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