From owner-freebsd-hackers Fri Jul 30 9:54:55 1999 Delivered-To: freebsd-hackers@freebsd.org Received: from apollo.backplane.com (apollo.backplane.com [209.157.86.2]) by hub.freebsd.org (Postfix) with ESMTP id 7F8F9151EB for ; Fri, 30 Jul 1999 09:54:40 -0700 (PDT) (envelope-from dillon@apollo.backplane.com) Received: (from dillon@localhost) by apollo.backplane.com (8.9.3/8.9.1) id JAA91354; Fri, 30 Jul 1999 09:51:35 -0700 (PDT) (envelope-from dillon) Date: Fri, 30 Jul 1999 09:51:35 -0700 (PDT) From: Matthew Dillon Message-Id: <199907301651.JAA91354@apollo.backplane.com> To: Alan Cox Cc: David Greenman , hackers@freebsd.org Subject: Re: patch for behavior changes and madvise MADV_DONTNEED References: <199907162234.PAA21850@apollo.backplane.com> <19990720014804.A21777@cs.rice.edu> <199907291856.LAA77471@apollo.backplane.com> <19990730000528.L10860@cs.rice.edu> Sender: owner-freebsd-hackers@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG :Your new "behavior" flag isn't known by vm_map_simply_entry, so :map simplification could drop the behavior setting on the floor. :I would prefer that the behavior is folded into eflags. : :Overall, I agree with the direction. Behavior is correctly a map :attribute rather than an object attribute. : : Alan : :P.S. The MADV_FREE's by malloc/free were disabled by default in -CURRENT :and -STABLE prior to the release of 3.2. They were a performance :pessimization, slowing down "make world" by ~2%. No problem, I think the behavior can easily be folded into eflags, which deals with the map simplification code as well. I'll work up a new patch. - I'm not sure I see how MADV_FREE could slow performance down unless, perhaps, it is the overhead of the system call itself. e.g. if malloc is calling it on a page-by-page basis and not implementing any hysteresis. 2% isn't a big deal. MADV_FREE theoretically makes a big impact on paging performance in a heavily loaded & paging system. If your tests were run on a system that wasn't paging, you weren't testing the right thing. -Matt Matthew Dillon To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message