From owner-freebsd-arch Wed Mar 13 2:16:44 2002 Delivered-To: freebsd-arch@freebsd.org Received: from flood.ping.uio.no (flood.ping.uio.no [129.240.78.31]) by hub.freebsd.org (Postfix) with ESMTP id 736E437B405; Wed, 13 Mar 2002 02:16:40 -0800 (PST) Received: by flood.ping.uio.no (Postfix, from userid 2602) id 6C5F75346; Wed, 13 Mar 2002 11:16:37 +0100 (CET) X-URL: http://www.ofug.org/~des/ X-Disclaimer: The views expressed in this message do not necessarily coincide with those of any organisation or company with which I am or have been affiliated. To: Josef Karthauser Cc: arch@freebsd.org, peter@freebsd.org, jake@freebsd.org Subject: Re: dumpsys() rewrite References: <20020313093805.GA29679@genius.tao.org.uk> From: Dag-Erling Smorgrav Date: 13 Mar 2002 11:16:37 +0100 In-Reply-To: <20020313093805.GA29679@genius.tao.org.uk> Message-ID: Lines: 19 User-Agent: Gnus/5.0808 (Gnus v5.8.8) Emacs/21.1 MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: owner-freebsd-arch@FreeBSD.ORG Precedence: bulk List-ID: List-Archive: (Web Archive) List-Help: (List Instructions) List-Subscribe: List-Unsubscribe: X-Loop: FreeBSD.ORG Josef Karthauser writes: > It would be fantastic to be able to compress the memory image as it is > dumped to disk. That would speed it up a bit in most cases. If each > dump_write reads memory directly rather than going through a common > function this is never going to be easy to do. dumpsys() controls what is written and when. It is perfetly conceivable for dumpsys() to do the same kind of hole compression that savecore(1) does, but it would be *much* slower and it would have to record information about every hole to disk, which would make savecore(1) slower as well. Currently, most drivers write 64 kB at a time when dumping, and savecore(1) reads 1 MB at a time. To perform hole compression, dumpsys() would have to scan through memory word by word *and* potentially write in far smaller increments than 64 kB. Remember the bad old days when it wrote only a sector at a time? DES -- Dag-Erling Smorgrav - des@ofug.org To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-arch" in the body of the message