On Tue, Apr 15, 2003 at 03:19:14PM -0700, Steve Taylor wrote: > Hello All, I am hoping some of you mips-linux gurus will be able to > help me give me some tips and help me get started on some cache stuff which > I want to do. (I know decently well about caches - but only at a > theoretical Hennessy & Patterson level - and have just started looking > under arch/mips/mm to familiarize myself with the mips-linux > implementation). Here's what I want to do - I have a CPU with 4 way SA I > and D caches, and I want to write a module that will lock a certain memory > region in these caches (for example, let's say I want to lock the ISR in > the I-cache). So my questions are > a) Is the kernel going to crash if I try to mess around with the caches > like locking out a particular way of the cache or something like that? > b) I'm sure there are many issues and > complications involved in this that I probably havent even thought of - > any obvious and/or subtle pitfalls? and c) Do you think locking out, say, > an entire way of a 4-way cache for a dedicated frequently used routine > improves or degrades overall system performance? General wisdom says locking is rarely a win but a loss unless you have particularly pathological access patterns which is not so likely with a 4-way cache. Cache locking is primarily useful if you are doing hard realtime stuff and need execution time deterministic to the absolute technical limit - even if at cost of latency and throughput. Linux being a general purpose UNIX clone is hardly the OS for such an application ... Ralf
