Date: Wed, 03 Mar 2004 23:36:05 -0500 From: "Simon" <simon@optinet.com> To: "Erich Dollansky" <oceanare@pacific.net.sg> Cc: "hardware@freebsd.org" <hardware@freebsd.org> Subject: Re: Xeon w/ L3 1MB cache vs Xeon w/o L3 cache Message-ID: <20040304043551.3A51E43D1D@mx1.FreeBSD.org> In-Reply-To: <4046AEE0.4010201@pacific.net.sg>
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Thanks, I read that under higher loads, the L3 cache becomes quite useful, too. But, what is considered high-load? what determines if L3 cache is used or not? is it app to the app to use it? or up to the kernel? or the CPU itself? or a combination? We run a lot of services on our servers and I would say they are heavy loaded, but I could be mistaking, I mean, they do a lot of processing but not exactly crawling, they are still fast. Thanks, Simon On Thu, 04 Mar 2004 12:21:52 +0800, Erich Dollansky wrote: >Hi, > >Simon wrote: > >> Has anyone done any comparison to see if extra L3 cache on Xeon CPUs >> provides any benefit to FreeBSD's kernel/core services and various user >> services' (http/email/ftp/databases) performance? I read that L3 can make >> things slower instead of faster in cases where L3 is not utilized and the CPU >> is forced to access it anyway (when L1/L2 don't hold the data it wants), >> because it exists. Would anyone with personal experience with Xeon CPUs >> with and without L3 cache comment on the impact of L3 cache. Any links >> to any related articles would be appreciated, as well. >> >I only have experience with other CPUs with L3 cache. L3 keeps >them faster under high load conditions. It made a small negative >impact under low load conditions because their L3 cache was much >slower than their L1 and L2 caches. > >If you have the high load it is worth the high price they cost. > >I do not have any links for this. The work was done some time ago >in a typical ISP environment. The tests included only FTP and >database. > >Erich >
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