Albert Cahalan writes: > The first is to avoid taking the initial fault on the segment > which contains the instruction pointer.
Good idea. > The second is to avoid cache or TLB invalidates or flushes > in certain circumstances. OpenBSD developers report that > this type of optimization is of great benefit on sparc and ppc. > It's an optimization than is only valid when no-execute is > in use, so the performance effects go both ways. We have a bit per page that says if the page is icache dirty or not. On machines with no-execute support, we already avoid flushing the page until some process first tries to execute from it. If we extended that to this scheme, when we made a segment executable, we would have to find and flush all icache-dirty pages in the segment (up to 65536 pages). We wouldn't want to do that every time we made a segment executable - it would need to be optimized (e.g. keep a count per segment of icache-dirty pages in the segment). Paul. -- To UNSUBSCRIBE, email to [EMAIL PROTECTED] with a subject of "unsubscribe". Trouble? Contact [EMAIL PROTECTED]
