On Thu, 2 Dec 2010, Eric Paris wrote: > sidtab_context_to_sid takes up a large share of time when creating large > numbers of new inodes (~30-40% in oprofile runs). This patch implements a > cache of 3 entries which is checked before we do a full context_to_sid lookup. > On one system this showed over a x3 improvement in the number of inodes that > could be created per second and around a 20% improvement on another system. > > Any time we look up the same context string sucessivly (imagine ls -lZ) we > should hit this cache hot. A cache miss should have a relatively minor affect > on performance next to doing the full table search. > > All operations on the cache are done COMPLETELY lockless. We know that all > struct sidtab_node objects created will never be deleted until a new policy is > loaded thus we never have to worry about a pointer being dereferenced. Since > we also know that pointer assignment is atomic we know that the cache will > always have valid pointers. Given this information we implement a FIFO cache > in an array of 3 pointers. Every result (whether a cache hit or table lookup) > will be places in the 0 spot of the cache and the rest of the entries moved > down one spot. The 3rd entry will be lost. This sounds a bit like a magazine cache -- should be useful. Have you thought about making it per-cpu ? -- James Morris <jmorris@xxxxxxxxx> -- This message was distributed to subscribers of the selinux mailing list. If you no longer wish to subscribe, send mail to majordomo@xxxxxxxxxxxxx with the words "unsubscribe selinux" without quotes as the message.
