On Thu, 21 Oct 2010 19:13:13 +0100 David Laight <da...@l8s.co.uk> wrote:
> A non-root user can then increase its own limit to 1/3 physmem, and > root can change its own 'hard' and 'soft' limits to any value it > cares. I think for some applications, having control over locking the entire physical memory can be a significant advantage. For example, for a network file server you can design a caching subsystem, which caches frequently accesses files and locks them in memory. On Linux or Solaris, you can mmap() those memory segments with larger pages to reduce TLB misses. The main benefit of locking is it guarantees those memory pages have not been flushed to disk, so your main threads never need to block. Any access to files not in your cache is done asynchronously, via a threaded I/O subsystem. I do realise this reinvents kernel file cache, but it gives you a lot more flexibility over what files get cached in memory and you can plug custom algorithms over how files get evicted from cache.
