Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933046AbWLJVXy (ORCPT ); Sun, 10 Dec 2006 16:23:54 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1762624AbWLJVXy (ORCPT ); Sun, 10 Dec 2006 16:23:54 -0500 Received: from smtp-vbr16.xs4all.nl ([194.109.24.36]:1224 "EHLO smtp-vbr16.xs4all.nl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1762616AbWLJVXy (ORCPT ); Sun, 10 Dec 2006 16:23:54 -0500 Date: Sun, 10 Dec 2006 22:23:51 +0100 From: Folkert van Heusden To: linux-kernel@vger.kernel.org Subject: optimalisation for strlcpy (lib/string.c) Message-ID: <20061210212350.GC30197@vanheusden.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Organization: www.unixexpert.nl X-Chameleon-Return-To: folkert@vanheusden.com X-Xfmail-Return-To: folkert@vanheusden.com X-Phonenumber: +31-6-41278122 X-URL: http://www.vanheusden.com/ X-PGP-KeyID: 1F28D8AE X-GPG-fingerprint: AC89 09CE 41F2 00B4 FCF2 B174 3019 0E8C 1F28 D8AE X-Key: http://pgp.surfnet.nl:11371/pks/lookup?op=get&search=0x1F28D8AE Read-Receipt-To: Reply-By: Mon Dec 11 21:32:58 CET 2006 X-Message-Flag: PGP key-id: 0x1f28d8ae - consider encrypting your e-mail to me with PGP! User-Agent: Mutt/1.5.13 (2006-08-11) Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2382 Lines: 95 Hi, Like the other patch (by that other person), I think it is faster to not do a strlen first. E.g. replace this: ize_t strlcpy(char *dest, const char *src, size_t size) { size_t ret = strlen(src); if (size) { size_t len = (ret >= size) ? size - 1 : ret; memcpy(dest, src, len); dest[len] = '\0'; } return ret; } by this: size_t strlcpy(char *dest, const char *src, size_t size) { char *tmp = dest; for(;;) { *dest = *src; if (!*src) break; if (--size == 0) break; dest++; src++; } *dest = 0x00; return dest - tmp; } patch: diff -uNrBbd lib/string.c string-new.c --- lib/string.c 2006-11-04 02:33:58.000000000 +0100 +++ string-new.c 2006-12-10 22:22:08.000000000 +0100 @@ -121,14 +121,24 @@ */ size_t strlcpy(char *dest, const char *src, size_t size) { - size_t ret = strlen(src); + char *tmp = dest; - if (size) { - size_t len = (ret >= size) ? size - 1 : ret; - memcpy(dest, src, len); - dest[len] = '\0'; + for(;;) + { + *dest = *src; + if (!*src) + break; + + if (--size == 0) + break; + + dest++; + src++; } - return ret; + + *dest = 0x00; + + return dest - tmp; } EXPORT_SYMBOL(strlcpy); #endif I've tested the speed difference with this: http://www.vanheusden.com/misc/kernel-strlcpy-opt-test.c and the speed difference is quite a bit on a P4: 28% faster. Signed-off by: Folkert van Heusden Folkert van Heusden -- www.vanheusden.com/multitail - multitail is tail on steroids. multiple windows, filtering, coloring, anything you can think of ---------------------------------------------------------------------- Phone: +31-6-41278122, PGP-key: 1F28D8AE, www.vanheusden.com - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/