Noam Meltzer wrote: > Hi, > > Quick answer is no. > A bit longer answer is: > 1- PAE refers to a certain technology avail. in the CPU which allows > 32bit kernels to address larger address spaces. > 2- Hugemem is a technology which changes the ratio between the user > space and kernel space from 3GB/1GB to 4GB/4GB. (So the actually > virtual memory refers to the same physical memory) It just gives your > processes a bit more a "breathing" space before starting > unmapping/mapping memory from highmem zone to the normal zone. Actually, if you read the original 4/4 patch, you will see that the two are not as unrelated as it may sound.
The purpose of the 4/4 split (which makes every call into the kernel more expensive, as it now requires switching the MMU address space) was NOT to give user space processes more breathing space. The purpose was to give the KERNEL more breathing space. The problem was that with PAE and several GB of memory, the kernel spent most of its 1GB address space on keeping track of where all its memory resides, and did not have enough memory for doing, well, pretty much anything else. The 4/4 split was not built to allow userspace the extra 1GB. The 4/4 split was meant to allow the kernel an extra 3GB. This is unlike the case for Windows, where Windows 2000 advanced server had a "revolutionary" 3/1 split, unlike the traditional 2/2 split for Windows 2000 server and workstation. I don't know what splits XP uses. > 3- In RHEL5 there's no need for a specific hugemem kernel anymore as > the kernel is smart enough to decide during boot what kind of > technology should it use. That does not make sense to me. The kernel can find out whether it needs more than 1GB for the kernel space during boot according to the amount memory available, and it can decide whether it needs PAE. I don't see how it can decide whether any user space program needs more than 3GB of space, however, during boot. > - Noam Shachar ================================================================= 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]
