Messages in this thread | | | Subject | Re: 2.5isms | From | Arjan van de Ven <> | Date | Sun, 02 Jan 2005 09:58:59 +0100 |
| |
> > I'm curious about a couple of points though. First, is that it is basically > just adding a cache colouring to the stack, right? In that case why do only > older HT CPUs have bad performance without it? And wouldn't it possibly make > even non HT CPUs possibly slightly more efficient WRT caching the stacks of > multiple processes?
it's a win on more than older HT cpus. It's just that those suffer it the most... (since there you have 2 "cpus" share the cache, meaning you get double the aliasing)
> Second, on what workloads does performance suffer, can you remember? I wonder > if natural variations in the stack pointer as the program runs would mitigate > the effect of this on all but micro benchmarks?
one of the problem cases I remember is network daemons all waiting in accept() for connections. All from the same codepath basically. Randomizing the stackpointer is a gain for that on all cpus that have finite affinity on their caches.
> But even if that were so so, it seems simple enough that I don't have any > real problem with keeping it of course.
The reason my patch does it much more is that it makes it a step harder to write exploits for stack buffer overflows.
- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
| |