From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mailserv2.iuinc.com (IDENT:qmailr@mailserv2.iuinc.com [206.245.164.55]) by puffin.external.hp.com (8.9.3/8.9.3) with SMTP id RAA06549 for ; Sun, 17 Dec 2000 17:47:12 -0700 From: Stan Sieler Message-Id: <200012180048.QAA03547@opus.allegro.com> Subject: Re: [parisc-linux] ldcw in __pthread_acquire To: alan@lxorguk.ukuu.org.uk (Alan Cox) Date: Sun, 17 Dec 2000 16:48:52 -0800 (PST) Cc: alan@lxorguk.ukuu.org.uk (Alan Cox), matthew@wil.cx (Matthew Wilcox), jes@linuxcare.com (Jes Sorensen), alan@linuxcare.com.au (Alan Modra), jsm@udlkern.fc.hp.com (John Marvin), parisc-linux@thepuffingroup.com In-Reply-To: from "Alan Cox" at Dec 18, 2000 12:36:06 AM MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii List-ID: Hi Alan, As Lamont Jones agreed, lightweight system calls exist, and their cost is on the order of a couple of instructions (typically the equivalent of a missed branch prediction). HP-UX has some, Lamont speaks from experience (as do I). > > The apparent advantages are *strictly* short term. A single mistake > > using a buzz lock from user code in a single process on a single computer > > can cost more time than all properly implemented buzz locks ever save. > > The cost of a syscall against a rarely contended lock is huge. So you Thus, it is *NOT* true that a syscall cost must be "huge". You can say: I don't want to change it, or "we've always done it that way". but, the one thing you can't accurately say is "this is the right way". Been there, learned that, tried to share it with you, and am now giving up on it. -- Stan (still right :) Sieler