Date: Tue, 21 Aug 2007 23:12:00 +0200 From: Maciej Sobczak <prog@msobczak.com> To: John Baldwin <jhb@freebsd.org> Cc: freebsd-arch@FreeBSD.org Subject: Re: Lockless uidinfo. Message-ID: <46CB5520.4090505@msobczak.com> In-Reply-To: <200708211403.29293.jhb@freebsd.org> References: <20070818120056.GA6498@garage.freebsd.pl> <20070818155041.GY90381@elvis.mu.org> <20070818161449.GE6498@garage.freebsd.pl> <200708211403.29293.jhb@freebsd.org>
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John Baldwin wrote: > Memory barriers on another CPU don't mean anything about the CPU thread 2 is > on. Of course they do. Otherwise they would be completely useless. > Memory barriers do not flush caches on other CPUs, etc. Membars are not about caches, but about visibility and ordering. Cache is transparent and that is guaranteed by hardware - there is no need to involve any software tricks to make cache work correctly. You can influence their performance, but not correctness. -- Maciej Sobczak : http://www.msobczak.com/ Programming : http://www.msobczak.com/prog/
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