From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Tue, 14 Sep 2004 19:45:55 -0300 From: Marcelo Tosatti Subject: Re: [PATCH] shrink per_cpu_pages to fit 32byte cacheline Message-ID: <20040914224555.GA714@logos.cnet> References: <20040913233835.GA23894@logos.cnet> <1095142204.2698.12.camel@laptop.fenrus.com> <20040914093407.GA23935@logos.cnet> <20040914111329.GB21362@devserv.devel.redhat.com> <20040914100152.GB23935@logos.cnet> <20040914114412.GC21362@devserv.devel.redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20040914114412.GC21362@devserv.devel.redhat.com> Sender: owner-linux-mm@kvack.org Return-Path: To: Arjan van de Ven Cc: akpm@osdl.org, "Martin J. Bligh" , linux-mm@kvack.org List-ID: On Tue, Sep 14, 2004 at 01:44:12PM +0200, Arjan van de Ven wrote: > On Tue, Sep 14, 2004 at 07:01:52AM -0300, Marcelo Tosatti wrote: > > On Tue, Sep 14, 2004 at 01:13:29PM +0200, Arjan van de Ven wrote: > > > On Tue, Sep 14, 2004 at 06:34:07AM -0300, Marcelo Tosatti wrote: > > > > How come short access can cost 1 extra cycle? Because you need two "read bytes" ? > > > > > > on an x86, a word (2byte) access will cause a prefix byte to the > > > instruction, that particular prefix byte will take an extra cycle during execution > > > of the instruction and potentially reduces the parallal decodability of > > > instructions.... > > > > OK thanks Arjan, where did you read this? The "Intel IA32 Optimization Guide" ? > > some version of that; I can't find it in my current one though. Hrmpf > Maybe there's someone from intel or amd on this list who can confirm the > performance impact of the 0x66 operand size override prefix Prefix "data16" I see... Well it doesnt seem anyone really familiar with this is part of the list - who you think would be sure about this? Jun Nakajima maybe? We need to be sure because we've just done for pagevec's. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: aart@kvack.org