Date: Wed, 2 Jan 2002 08:01:23 +1100 (EST) From: Bruce Evans <bde@zeta.org.au> To: Mike Smith <msmith@FreeBSD.ORG> Cc: Bernd Walter <ticso@cicely8.cicely.de>, Michal Mertl <mime@traveller.cz>, Matthew Dillon <dillon@apollo.backplane.com>, <arch@FreeBSD.ORG> Subject: Re: When to use atomic_ functions? (was: 64 bit counters) Message-ID: <20020102075650.L11121-100000@gamplex.bde.org> In-Reply-To: <200201012048.g01KmYr01192@mass.dis.org>
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On Tue, 1 Jan 2002, Mike Smith wrote: > > MBs are not needed for the variable itself, but they are making this > > family of functions very expensive. > > It's not very wise to handle counters with atomic_ functions unless > > the need to have MBs in them is not removed. > > It's imperative to use atomic operations for counters on SMP systems. Not true. Atomic operations for counters are not needed on SMP systems in at least the following cases: - if there is a lock that prevents other processes from accessing the counter - if the counters are per-CPU. See previous mail by someone named msmith. Bruce To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-arch" in the body of the message
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