Date: Sat, 11 Jul 1998 11:23:06 -0400 (EDT) From: zhihuizhang <bf20761@binghamton.edu> To: hackers <freebsd-hackers@FreeBSD.ORG> Subject: Question about shadow object collapse Message-ID: <Pine.SOL.L3.93.980711112150.758C-100000@sparky8>
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According to the Mach paper "Machine-Independent Virtual Memory Management for Paged Uniprocessor and Multiprocessor Architectures", a shadow object still relies on the original object (i.e., backing object) that it shadows for all unmodified data. If this is true in FreeBSD, can anyone explain the following comments found in the routine vm_object_collapse() (see source file vm/vm_object.c): (1) Pages that have been paged out will be overwirteen by any of the parent's pages that shadow them. (why so and how to know if a page has been paged out?) (2) If the page falls outside the parent, dispose of it. (why so?) Any help is appreciated. ------------------------------------------------- Zhihui Zhang Department of Computer Science State University of New York at Binghamton Web Site: http://cs.binghamton.edu/~zzhang ------------------------------------------------- To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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