Date: Wed, 8 Dec 1999 15:22:33 -0800 (PST) From: Matthew Dillon <dillon@apollo.backplane.com> To: Jason Young <doogie@anet-stl.com> Cc: Alfred Perlstein <bright@wintelcom.net>, freebsd-hackers@FreeBSD.ORG Subject: Re: Getting a new MAP_ flag into mmap() prior to 4.x freeze Message-ID: <199912082322.PAA44403@apollo.backplane.com> References: <Pine.BSF.3.96.991208164748.21221F-100000@earth.anet-stl.com>
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:I think that you imply explicit msync() calls still flush data to disk. Is
:that the case?
:
:Jason Young
:accessUS Chief Network Engineer
msync never guarenteed the flushing of data to disk, it simply guarentees
synchronization with the buffer cache. FreeBSD, however, uses a
coherent VM/buffer-cache.
The FreeBSD msync with the MS_SYNC flag appears to flush VM data
to physical media, though in my test it is terribly slow (it doesn't
cluster!). msync doesn't care whether the pages are NOSYNC or not.
i.e. NOSYNC has no effect on the operation of msync().
msync() with the MS_ASYNC flag appears to cluster properly.
-Matt
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