Messages in this thread | | | Date | Fri, 30 Apr 1999 08:50:36 +0200 (CEST) | From | Ingo Molnar <> | Subject | Re: 2.2.5 optimizations for web benchmarks? |
| |
On Fri, 30 Apr 1999, Stephen C. Tweedie wrote:
> > across many OSes. On the other hand, Apache in particular may not > > access enough memory to make a huge difference. > > Remember, this is TLB flushes, not cache flushes, we're talking about. > *Every* memory access after a TLB flush needs to reload the TLB, even if > it is just a read from already-cached memory. Even just spinning in > kernel space may require TLB refills after a flush (although newer > Pentia do let you mark certain page tables as global, so a mm replace > won't evict those TLBs).
yes and this is a pretty important effect. Also, a TLB miss on a Xeon with all the page table info cached takes 3 cycles (and does not cause a pipeline stall, so the real cost can be lower than this). So the cost for a TLB flush is not all that high as it seems at first sight.
-- mingo
- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.rutgers.edu Please read the FAQ at http://www.tux.org/lkml/
| |