Date: Wed, 8 Dec 1999 14:51:17 -0800 (PST) From: Alfred Perlstein <bright@wintelcom.net> To: Matthew Dillon <dillon@apollo.backplane.com> Cc: freebsd-hackers@FreeBSD.ORG Subject: Re: Getting a new MAP_ flag into mmap() prior to 4.x freeze Message-ID: <Pine.BSF.4.21.9912081447110.4557-100000@fw.wintelcom.net> In-Reply-To: <199912081721.JAA37897@apollo.backplane.com>
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On Wed, 8 Dec 1999, Matthew Dillon wrote: > I would like to add a new MAP_ flag to mmap() prior to the 4.x freeze. > The purpose of the flag is to prevent the syncer from syncing the > file underlying the map. The VM system will still page to the file as > needed and, of course, the data will remain consistent with the file. > > This will allow normal files to be used to back (for example) shared > memory without incuring the extra overhead that sync causes every 30 > seconds. Currently it is not possible to use normal files in this > fashion (verses using MAP_ANON, for which sharability is limited, or > SysV shared memory which often has unexpected limitations) and still > have an efficient system. > > The flag will be called MAP_NOSYNC > > Operationally, the syncer will not sync the file while any mmap()'s > exist with that flag set. Once such flagged maps go away, the syncer > will be able to sync the file (if it still exists). > > Comments are welcome. I'd like to see this happen, go for it! :) Don't forget how getnewbuf refils the buffers though, it will need to somehow to communicate to the syncer to disregard MAP_NOSYNC during a shortage... ? :) -Alfred To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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