Date: Fri, 8 Jan 1999 00:23:22 -0500 (EST) From: "John S. Dyson" <dyson@iquest.net> To: tlambert@primenet.com (Terry Lambert) Cc: dillon@apollo.backplane.com, tlambert@primenet.com, dyson@iquest.net, pfgiffun@bachue.usc.unal.edu.co, freebsd-hackers@FreeBSD.ORG Subject: Re: questions/problems with vm_fault() in Stable Message-ID: <199901080523.AAA00601@y.dyson.net> In-Reply-To: <199901080251.TAA03819@usr01.primenet.com> from Terry Lambert at "Jan 8, 99 02:51:20 am"
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Terry Lambert said: > > :The recovery mechanism you outline deals with breaking pages back > > :to the system for reuse, but *aggrivates* the fragmentation issue > > :to an almost unholy level, which just gets worse if you try and add > > :cylinder groups to "grow" the MFS. > > > > No it doesn't. Explain to me how it aggravates the fragmentation > > issue. Remember, we *don't* *care* how 'fragmented' the file data > > is in MFS's device namespace. We just care how fragmented it is on > > physical media - the swap backing store. The swapper automatically > > defragments anything over a page in size. > > Kernel VM space fragmentation. > > Try to load a quiccam driver KLD that need to malloccontig. > Aiiieee!!! The kernel doesn't care about virtual addresses at all, and the issue of malloccontig is only an issue of not going to the trouble of reallocating KVA space. This has NOTHING to do with pages used for storage: KVA (kernel virtual address) space is highly decoupled from memory, and in fact is more expensive in many ways than bulk memory. The system in general has little or no support for contiguous memory, and that issue is orthogonal to any of the discussions herein (other than the bogusness of synthetic entities such as bp's that imply often unneeded kernel KVA mappings.) -- John | Never try to teach a pig to sing, dyson@iquest.net | it makes one look stupid jdyson@nc.com | and it irritates the pig. To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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