From owner-freebsd-hackers Mon Jan 26 23:05:23 1998 Return-Path: Received: (from majordom@localhost) by hub.freebsd.org (8.8.8/8.8.8) id XAA25197 for hackers-outgoing; Mon, 26 Jan 1998 23:05:23 -0800 (PST) (envelope-from owner-freebsd-hackers@FreeBSD.ORG) Received: from dyson.iquest.net (dyson.iquest.net [198.70.144.127]) by hub.freebsd.org (8.8.8/8.8.8) with ESMTP id XAA25159 for ; Mon, 26 Jan 1998 23:05:08 -0800 (PST) (envelope-from toor@dyson.iquest.net) Received: (from root@localhost) by dyson.iquest.net (8.8.8/8.8.8) id CAA27777; Tue, 27 Jan 1998 02:03:21 -0500 (EST) (envelope-from toor) Message-Id: <199801270703.CAA27777@dyson.iquest.net> Subject: Re: File I/O in kernel land (was: Re: 2nd warning: 2.2.6 BETA begins in 10 days!) In-Reply-To: <199801270637.AAA04478@detlev.UUCP> from Joel Ray Holveck at "Jan 27, 98 00:37:51 am" To: joelh@gnu.org Date: Tue, 27 Jan 1998 02:03:21 -0500 (EST) Cc: mike@smith.net.au, dag-erli@ifi.uio.no, hackers@FreeBSD.ORG From: "John S. Dyson" Reply-To: dyson@FreeBSD.ORG X-Mailer: ELM [version 2.4ME+ PL32 (25)] MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-freebsd-hackers@FreeBSD.ORG Precedence: bulk Joel Ray Holveck said: > > My real concern is holding on to lots of dynamically allocated kernel > memory, which is something I can't see getting around without the > screen saver doing file I/O. In Linux, dynamic kernel memory was a > precious resource. Is it not so in FreeBSD? > In FreeBSD, the kernel address space should be carefully used, but it is not any more precious than statically allocated kernel memory. We are currently limited to a little less than 256MB kernel virtual size. Almost everything like buffer space, and temporary type mappings, etc. are dynamically allocated, and most of the buffer space isn't normally mapped anyway. That KVA size is almost always adequate for workstation applications, for almost any memory size. However, for server apps, you can rebuild the kernel with a few mods so that you can run with KVA size of 512MB or 1GB (but isn't needed, except on machines with lots and lots of TCP connections, etc.) -- John | Never try to teach a pig to sing, dyson@freebsd.org | it just makes you look stupid, jdyson@nc.com | and it irritates the pig.