Re: Availability of kdb

From: Jeff V. Merkey (jmerkey@timpanogas.com)
Date: Mon Sep 11 2000 - 14:54:59 EST


I'll give it some thought. Most of Linux has better paging than NetWare
already -- NetWare is pretty simple in this respect. THe process
mapping stuff in Netware (PCB's are mapped to recursively point to
themselves with a global brach table) is unique, but not as good as
what's in Linux.

:-)

Jeff

Jamie Lokier wrote:
>
> Jeff V. Merkey wrote:
> > One of the best references that describes the bus transaction model for
> > Intel in "plain english" is the Pentium Pro Processor System
> > Architecture Manual by Tom Shanley of Mindshare, Inc., Addison Wesley,
> > ISBN: 0-201-47953-2. It explains a very good detail how the cache
> > controllers and MESI works on Intel.
>
> Agreed, it is a very informative book. More detail than you need unless
> you're cloning the chips ;-) Full of good ideas, especially for anyone
> interested in memory hierarchies.
>
> > In NetWare, we didn't care if the page was touched or not since we
> > used our own bits in field bits 11-9 to store page specific stuff,
> > like whether the page was dirty or not.
>
> Linux does actually look at both bits, but the optimisation still
> applies. Accessed in particular -- ptes are mapped on page faults so
> you know the page is about to be accessed.
>
> > We saw a 4% performance improvement for Network I/O by avoiding the
> > "hidden" locking in Intel's architecture. You should check if you need
> > this bit, and if not, always create the PTE with it set. I don't know
> > how much it would help Linux. NetWare is well optimized for Intel
> > processors and any little thing that increased bus memory utilization
> > was very noticeable on NetWare, since it supports such huge user loads
> > already.
> >
> > :-)
>
> Use Linux. Grok Linux. Read the source and weep :-)
> But thanks for the tip :-)
>
> Btw, any good tips you have on effective paging heuristics -- now they
> _would_ be useful I'm sure. Linux paging is still rather experimental
> after all these years. As in, it works but could do better.
>
> -- Jamie
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