On Saturday 05 of September 2015 00:37:10 Per Jessen wrote:
Not about scarcity at all - most of my servers have 24Gb and they run a LOT of postfix instances. A lot more in 32bit than in 64bit mode. (some servers have less and no more space for more memory, but that's hardly a reason to upgrade).
(Assuming you actually meant 24 GB rather than 24 Gb as using gigabits for memory sizes would be quite unusual. If you really wanted to say "24 Gb" (i.e. 3 GB), please ignore.) When you talked about memory efficiency, I somehow expected you to run systems with up to 4 GB of RAM, 8 GB in the worst case. I never imagined you would want to run a 32-bit kernel with PAE on a 24GB machine. That would be completely insane. You should realize a 32-bit kernel has ~896 MB of low memory and almost all kernel data structures must fit into it. The biggest of them is the mem_map array holding a struct page (56 B on i586) for each page of physical memory. In your case, just this array would take (24 GB / 4 KB) * 56 B = 352321536 B ~ 336 MB of your precious low memory. As a result, all other kernel data structures including process (kernel) stacks, page cache, file buffers, socket buffers etc. must fit into the remaining 560 MB. It would be really interesting to profile your system and see how much CPU time it wastes on remapping memory and flushing pages into and out of the page cache. You should consider migrating to at least a 64-bit kernel even if you insist on 32-bit userspace. Michal Kubeček -- To unsubscribe, e-mail: opensuse-factory+unsubscribe@opensuse.org To contact the owner, e-mail: opensuse-factory+owner@opensuse.org