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" <wyu@talisys.com>
>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:
>> William,
>>
>>
>>>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?
>>
