Date: Sun, 23 Feb 2003 10:35:37 +0000 From: Christoph Hellwig <hch@infradead.org> To: Terry Lambert <tlambert2@mindspring.com> Cc: Byunghyun Oh <octphial@postech.ac.kr>, freebsd-hackers@freebsd.org Subject: Re: Replacement for get_user_pages() of Linux Message-ID: <20030223103537.A16012@infradead.org> In-Reply-To: <3E589FB3.46C1AAB2@mindspring.com>; from tlambert2@mindspring.com on Sun, Feb 23, 2003 at 02:17:23AM -0800 References: <20030223163746.A19421@shell.postech.ac.kr> <3E588B1B.484C4D61@mindspring.com> <20030223094958.A15347@infradead.org> <3E589FB3.46C1AAB2@mindspring.com>
next in thread | previous in thread | raw e-mail | index | archive | help
On Sun, Feb 23, 2003 at 02:17:23AM -0800, Terry Lambert wrote: > OK, you mean "make non-pageable". Well, I didn't write the initial mail :) > The question, I guess, is "why?". Are you trying to do a delayed > operation that will complete when the process has otherwise been > swapped out? well, I don't plan to do anything. The usual way get_user_pages is used on linux is: get_user_pages() perform scatter gatter dma to some device on the pages unping pages as linux VM scanning is fully mutithreaded pages could get paged out during the dma if you didn't pin them so this is needed. > > get_user_pages() does not establish a mapping, in Linux you don't need > > a kernel mapping to perform DMA on memory. > > In FreeBSD, you generally do. First off, the VM and buffer cache is > unified. That means that's there's no such thing as a buffer that > exists seperately from the VM system. Who talks about buffers? And yes, in Linux you can have buffers that have pages attached to it that aren't mapped into kernel virtual space, in fact that's usual for pages used for actual filesystem data if you have enough memory. To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?20030223103537.A16012>