Date: Sun, 5 Apr 1998 20:46:01 -0500 (EST) From: "John S. Dyson" <toor@dyson.iquest.net> To: tweten@frihet.com (David E. Tweten) Cc: dswartz@druber.com, dyson@FreeBSD.ORG, dg@root.com, dag-erli@ifi.uio.no, stable@FreeBSD.ORG Subject: Re: swap-leak in 2.2.5 ? Message-ID: <199804060146.UAA06954@dyson.iquest.net> In-Reply-To: <199804060140.SAA03046@ns.frihet.com> from "David E. Tweten" at "Apr 5, 98 06:40:39 pm"
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> > The 4.4 BSD interaction between physical pages used for virtual memory and > physical pages used for file system cache doesn't work that way, and I can't > imagine the FreeBSD core team adding in such a botch. It is never a good > idea to send a dirty file system cache page to swap. It is always better to > send it to the file system. After all, it might never again be written. If > it is ever written, it will have to be read into memory again either way. > Of course, we write dirty pages only to the correct place. > > What you see in swap under heavy I/O load, is dirty process virtual memory > pages moved out of real memory to make way for an expanding file system > cache. There's no reason to read them back until the process faults for > them; it might exit first, allowing you to just abandon them. > Our filesystem cache applies only very slight pressure to process memory. Indeed much less than most other OSes. John To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-stable" in the body of the message
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