Date: Sat, 14 Dec 1996 21:06:28 +0100 From: Poul-Henning Kamp <phk@critter.tfs.com> To: dyson@freebsd.org Cc: peter@spinner.dialix.com (Peter Wemm), smp@freebsd.org, haertel@ichips.intel.com Subject: Re: some questions concerning TLB shootdowns in FreeBSD Message-ID: <5557.850593988@critter.tfs.com> In-Reply-To: Your message of "Sat, 14 Dec 1996 13:38:47 EST." <199612141838.NAA00208@dyson.iquest.net>
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In message <199612141838.NAA00208@dyson.iquest.net>, "John S. Dyson" writes: >The way that I see it, is that the current pmap code is highly optimized >for single processor operation. If I was you, I would try to just >try to get something working correctly algorithmically -- almost ignoring >performance issues. Of course, when performance is easy -- go for that >also. > >Alot of things like single page invalidates inside of loops appear that >they could be evil for multi-processor applications (imagine an inter- >processor interrupt for every loop!?!?.) I think that you (we or us), >will have to look at the performance for the SMP direction, and it >might even entail large differences in pmap eventually. Hopefully, >we will all be able to isolate the differences for the maintenance of >sanity :-). The crucial thing, as far as I can see, is to find out >if< we need to tell the other CPU's about this change to the pagetables. For a 2cpu system the penalty of stopping the other CPU is still within bounds of the reasonable, but stopping three CPUs needlessly is not a good idea. Is there any cheap way to keep a refcount (or bitmap) per vm-object so we can see if we need to kick the other CPUs if we fiddle it ? -- Poul-Henning Kamp | phk@FreeBSD.ORG FreeBSD Core-team. http://www.freebsd.org/~phk | phk@login.dknet.dk Private mailbox. whois: [PHK] | phk@tfs.com TRW Financial Systems, Inc. Power and ignorance is a disgusting cocktail.
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