Date: Mon, 07 Oct 2002 15:03:19 -0700 From: Terry Lambert <tlambert2@mindspring.com> To: Peter Wemm <peter@wemm.org> Cc: Mikhail Teterin <mi+mx@aldan.algebra.com>, arch@FreeBSD.org Subject: Re: swapon some regular file Message-ID: <3DA204A7.50530BE5@mindspring.com> References: <20021007212545.C363B2A88D@canning.wemm.org>
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Peter Wemm wrote: > > Users wishing to swap onto a local regular file have to go through the > > vnconfig/mdconfig gimnastics. Is that intentional? > > Yes, it is quite intentional. swap_pager doesn't have the code to do > logical to physical translation that file IO would require. And the > VOP_BMAP calls that do that add new complications, including an additional > place it can sleep or run out of memory. > > We can get away with it for swapping to a file over NFS because the remote > server does the translation, not us. > > In reality, what is required is some careful cut/paste of code from > vnode_pager to swap_pager to add the missing bits, and some care to deal > with the complications. > > vnconfig/mdconfig work because that basically adds the logical -> physical > translation step. I'd just as soon not have to mess with this though. It would be useful to be able to ask a file for its list of physical blocks on the underlying device, so that you could sort them into contiguous extents, and then use *those*, instead of eating the translation overhead, each time... -- Terry To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-arch" in the body of the message
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