Re: [benchmark] 2.4.0-test6-pre1 PAE vs non-PAE

From: Tigran Aivazian (
Date: Thu Aug 03 2000 - 11:24:25 EST

Hi Ingo!

On Thu, 3 Aug 2000, Ingo Molnar wrote:
> the 3% performance drop

that is 6, not 3. 129.6/136.5 = 0.94945054945054945054 ~ 0.94 (ok, 0.95
but no way it is 0.97 :)

> is mainly due to two values, 'Pipe-based Context Switching',
>'Process Creation', and 'Execl Throughput'.

that is 3, not 2.

the rest of your mail makes perfect sense, thank you.

> The fork() and
> exec() result is understandably worse with PAE, because the 'density' of
> page-tables is half of that of non-PAE page-tables (ie. twice as much has
> to be copied), plus there are 3 user-space root page tables instead of the
> 1. (which have to be zeroed, so this shows up big time.)
> Another performance problem is likely the amount of LOCK-ed instructions
> done within the PAE include-files - some of that is unnecessery as David
> S. Miller noticed.
> otherwise the PAE kernels show no performance drop in 'typical' user-space
> stuff. But yes, you dont want to use it on a box with less than 4GB RAM.


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