Date: Mon, 18 Dec 1995 20:13:27 -0800 From: David Greenman <davidg@Root.COM> To: A JOSEPH KOSHY <koshy@india.hp.com> Cc: freebsd-questions@freebsd.org Subject: Re: Undumping vs. MMAP'ing Message-ID: <199512190414.UAA02973@corbin.Root.COM> In-Reply-To: Your message of "Tue, 19 Dec 95 09:15:42 %2B0530." <199512190345.AA128034742@fakir.india.hp.com>
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>A question for VM people: > >If I remember right, the rationale behind Emacs dumping and unexecing >itself was to be able to move byte-compiled lisp code into its text segment >so that it could be shared across multiple invocations of the program. > >Now will this sharing be done by the VM layer in FreeBSD if I mmap a file >read-only and shared across multiple processes? Yes, if multiple processes map a file the memory will be shared. If the file is mapped read/write shared, then changes made by others will be seen in all processes. If the file is mapped "MAP_PRIVATE", then changes will not be seen by other processes (the modified page is first copied), but unmodified portions will continue to be shared. -DG
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