Messages in this thread | | | From | Andrew Theurer <> | Subject | Re: Linux 2.4.19-rc3 (hyperthreading) | Date | Mon, 29 Jul 2002 14:54:30 -0500 |
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I would caution against having hyperthreading on by default in the 2.4.19 release. I am seeing a significant degrade in network workloads on P4 with hyperthreading on. On 2.4.19-pre10, I get 788 Mbps on NetBench, but on 2.4.19-rc1 (and probably rc3, should know in an hour), I get 690 Mbps. It is clearly a hyperthreading/interrupt routing issue. On this system (4 x P4), with no hyperthreading, there is enough CPU to handle all interrupts on CPU0 (this is where all ints go by default). With hyperthreading on, I get "1/2" of a CPU for interrupt processing. What ends up happenning is that CPU0 is at 100%, while CPU1-CPU7 are at 75%. Now I know the "noth" is available, but since hyperthreading is not proven to give a performance boost to more than 1/2 of the common workloads for linux users (or is it? who has done tests?), I'd like to see this default behavior reversed, and still use acpismp=force to enable hyperthreading.
Also, If anyone has performance results for their workloads showing a boost with hyperthreading, I would really like to know.
-Andrew Theurer
<<So here goes rc3. Another -rc is going to come only in the case of really critical problem(s).
I'm attaching the rc2->rc3 changelog only because the full changelog got too big (I guess thats why my -rc2 announce mail didnt go to lk).>>
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