On Wed, Apr 21, 2010 at 12:53 PM, Gilboa Davara <gilb...@gmail.com> wrote:
> In my experience (running a kernel based packet inspection software), HT > on Xeon 55xx yields around 15-20% performance benefit. (YMMV, of-course) YMMV is the operative term here. Shachar is right: the main problem with HT is increased cache contention for unrelated processes (causing "cache thrashing"). This may degrade performance for memory-intensive applications. This is the principal reason why many people switched HT off. Shimi's "belief" that performance was degraded for a single process is likely due to the same reason. There is no such thing as a single process in a general purpose system. One may be "interesting", but it still may occasionally be evicted from cache by an "uninteresting" one that no one notices. If your workload does not lead to this kind of problem chances are HT can be beneficial. Side note: apart from HT there was also "superthreading" once. That aimed at reducing memory latency - different threads were interleaved in the CPU's pipeline (but only one thread per stage) - but had no instruction-level parallelism. IIRC, it did not look as multi-CPU to the OS (HT did). Can you even buy a computer with just one CPU/core today? -- Oleg Goldshmidt | o...@goldshmidt.org _______________________________________________ Linux-il mailing list Linux-il@cs.huji.ac.il http://mailman.cs.huji.ac.il/mailman/listinfo/linux-il
