On Thu, Aug 09, 2007 at 02:59:02PM +0300, Ira Abramov wrote: > Quoting Muli Ben-Yehuda, from the post of Thu, 09 Aug: > > > > Because some PCI devices cannot deal with addresses over 4G. To be > > able to map the RAM that has physical address over 4G in the CPU's > > page tables, you need a PAE kernel. As for the penalty on speed, I > > doubt you'll be able to measure it, and it will be offset by the extra > > RAM. > > According to Marc (who is a man I don't like to disagree with) it's > a hit of 3-5% on average on grid machines if I recall.
I would like to understand this better, if you or Marc could shed more details? In general, I believe you know what they say about "lies, damn lies, and performance numbers". See some numbers from Ingo Molnar which give the PAE overhead at a round 0.0% here: http://kerneltrap.org/node/2891. YMMV. 100Hz 100.00% 100Hz + PAE: 0.00% 1000Hz: -1.08% 1000Hz + PAE: -1.08% Cheers, Muli ================================================================= To unsubscribe, send mail to [EMAIL PROTECTED] with the word "unsubscribe" in the message body, e.g., run the command echo unsubscribe | mail [EMAIL PROTECTED]
