From owner-freebsd-hackers@FreeBSD.ORG Fri Jul 6 16:44:50 2007 Return-Path: X-Original-To: freebsd-hackers@freebsd.org Delivered-To: freebsd-hackers@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [69.147.83.52]) by hub.freebsd.org (Postfix) with ESMTP id D294416A400 for ; Fri, 6 Jul 2007 16:44:50 +0000 (UTC) (envelope-from rwatson@FreeBSD.org) Received: from cyrus.watson.org (cyrus.watson.org [209.31.154.42]) by mx1.freebsd.org (Postfix) with ESMTP id A3E7913C4CB for ; Fri, 6 Jul 2007 16:44:50 +0000 (UTC) (envelope-from rwatson@FreeBSD.org) Received: from fledge.watson.org (fledge.watson.org [209.31.154.41]) by cyrus.watson.org (Postfix) with ESMTP id DEDE8491D0; Fri, 6 Jul 2007 12:44:49 -0400 (EDT) Date: Fri, 6 Jul 2007 17:44:49 +0100 (BST) From: Robert Watson X-X-Sender: robert@fledge.watson.org To: Julian Elischer In-Reply-To: <468E7007.5050607@elischer.org> Message-ID: <20070706174321.M17956@fledge.watson.org> References: <20070705122650.GE1302@britannica.bec.de> <468E16E6.6030608@delphij.net> <20070706112453.GA3217@hoeg.nl> <468E7007.5050607@elischer.org> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII; format=flowed Cc: FreeBSD Hackers , d@delphij.net, Ed Schouten Subject: Re: add closefrom() call X-BeenThere: freebsd-hackers@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Technical Discussions relating to FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 06 Jul 2007 16:44:50 -0000 On Fri, 6 Jul 2007, Julian Elischer wrote: > Ed Schouten wrote: >> * LI Xin wrote: >>> Here is my implementation for FreeBSD. Some difference between my and >>> DragonFly's implementation: >>> >>> - closefrom(-1) would be no-op on DragonFly, my version would close all >>> open files (From my understanding of OpenSolaris's userland >>> implementation, this is Solaris's behavior). >>> - my version closefrom(very_big_fd) would result in EBADF. I am not very >>> sure whether this is correct, but it does not hurt for applications that >>> thinks closefrom() would return void. >> >> Wouldn't it be better to just implement it through fcntl() and implement >> closefrom() in libc? > > that's a possibility but I personally thing the huge difference in > efficiency makes it worth putting it in the kernel. Quite a few programs I > know of could really help their startup time with this as the first thing > they do is "close the first 2000 file descriptors. The Solaris implementation appears to implement two strategies: (1) If procfs is mounted, list the fd directory to get a list of open fds, then close those by number. (2) If procfs is not mounted, query the number of open fds using the resource limit interface, then sequentially close until the right number close. Hence my question as to whether there's actually a big benefit or not -- do we think closefrom() is a performance-critical function? Robert N M Watson Computer Laboratory University of Cambridge