Date: Thu, 23 Mar 2000 15:12:20 -0800 From: Greg Lehey <grog@lemis.com> To: Poul-Henning Kamp <phk@critter.freebsd.dk> Cc: Matthew Dillon <dillon@apollo.backplane.com>, current@FreeBSD.ORG Subject: Re: patches for test / review Message-ID: <20000323151220.A9318@mojave.worldwide.lemis.com> In-Reply-To: <20074.953579833@critter.freebsd.dk>; from phk@critter.freebsd.dk on Mon, Mar 20, 2000 at 08:17:13PM %2B0100 References: <200003201846.KAA70820@apollo.backplane.com> <20074.953579833@critter.freebsd.dk>
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On Monday, 20 March 2000 at 20:17:13 +0100, Poul-Henning Kamp wrote: > In message <200003201846.KAA70820@apollo.backplane.com>, Matthew Dillon writes: > >> Well, let me tell you what the fuzzy goal is first and then maybe we >> can work backwards. >> >> Eventually all physical I/O needs a physical address. The quickest >> way to get to a physical address is to be given an array of vm_page_t's >> (which can be trivially translated to physical addresses). > > Not all: PIO access to ATA needs virtual access. RAID5 needs > virtual access to calculate parity. I'm not sure what you mean by "virtual access". If you mean file-related rather than partition-related, no: like the rest of Vinum, RAID-5 uses only partition-related offsets. >> What we want to do is to try to extend VMIO (aka the vm_page_t) all >> the way through the I/O system - both VFS and DEV I/O, in order to >> remove all the nasty back and forth translations. > > I agree, but some drivers need mapping we need to cater for those. > They could simply call a vm_something(struct buf *) call which would > map the pages and things would "just work". > > For RAID5 we have the opposite problem also: data is created which > has only a mapped existance and the b_pages[] array is not > populated. Hmm. I really need to check that I'm not missing something here. Greg -- Finger grog@lemis.com for PGP public key See complete headers for address and phone numbers To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-current" in the body of the message
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