This must be a linux'ism because to my knowledge FreeBSD does not keep the os-cache mapped into the kernel address space unless it have active objects associated with the data.

And FreeBSD also have a default split of 3GB userspace and 1GB. kernelspace when running with a default configuration. Linux people might want to try other os'es to compare the performance.

Best regards,
Nicolai Petri

Ps. Sorry for my lame MS mailer - quoting is not something it knows how to do. :)
----- Original Message ----- From: "William Yu" <[EMAIL PROTECTED]>

I inferred this from reading up on the compressed vm project. It can be higher or lower depending on what devices you have in your system -- however, I've read messages from kernel hackers saying Linux is very aggressive in reserving memory space for devices because it must be allocated at boottime.

Josh Berkus wrote:

The theshold for using PAE is actually far lower than 4GB. 4GB is the
total memory address space -- split that in half for 2GB for userspace,
2GB for kernel. The OS cache resides in kernel space -- after you take
alway the memory allocation for devices, you're left with a window of
roughly 900MB.

I'm curious, how do you get 1.1GB for memory allocation for devices?

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