Xeon w/ L3 1MB cache vs Xeon w/o L3 cache

[Simon]

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
>