Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Fri, 7 Dec 2001 13:36:32 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Fri, 7 Dec 2001 13:36:22 -0500 Received: from eventhorizon.antefacto.net ([193.120.245.3]:62338 "EHLO eventhorizon.antefacto.net") by vger.kernel.org with ESMTP id ; Fri, 7 Dec 2001 13:36:02 -0500 Message-ID: <3C110C0B.4030102@antefacto.com> Date: Fri, 07 Dec 2001 18:35:55 +0000 From: Padraig Brady User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:0.9.6) Gecko/20011120 X-Accept-Language: en-us MIME-Version: 1.0 To: Michael Poole CC: Andi Kleen , Linus Torvalds , linux-kernel@vger.kernel.org Subject: Re: horrible disk thorughput on itanium In-Reply-To:

<20011207185847.A20876@wotan.suse.de> <87wuzyq4ms.fsf@sanosuke.troilus.org> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Michael Poole wrote: > Andi Kleen writes: > > >>>You can be thread-safe without sucking dead baby donkeys through a straw. >>>I already mentioned two possible ways to fix it so that you have locking >>>when you need to, and no locking when you don't. >>> >>Your proposals sound rather dangerous. They would silently break recompiled >>threaded programs that need the locking and don't use -D__REENTRANT (most >>people do not seem to use it). I doubt the possible pain from that is >>worth it for speeding up an basically obsolete interface like putc. >> >>i.e. if someone wants speed they definitely shouldn't use putc() >> > > Threaded programs that need locking and don't define _THREAD_SAFE or > _REENTRANT or whatever is appropriate are already broken -- they just > don't know it yet. > > FreeBSD #defines putc and getc to their unlocked versions unless > _THREAD_SAFE is defined, and people don't seem to think its libc is > broken. Many lightly threaded programs, in fact, wouldn't need or > even want the locked variants to be the default. One app I've worked > with only reads and writes any given FILE* from one thread, and I saw > an 4x speedup by switching to the unlocked variants. This breaks for the case discussed @ http://sources.redhat.com/ml/bug-glibc/2001-11/msg00079.html I.E. if you have a multithreaded lib being linked by single threaded apps (Note multithreaded lib, not just a threadsafe lib (I.E. the lib calls pthread_create())). Padraig. - 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/