> How about this patch? Instead of making a per-cpu trampoline, write to
> the msr during each context switch. This means that the stack pointer
> is valid at all times, and also saves memory and a cache line bounce. I
> also included some misc cleanups.
Just a little bit of benchmarking:
(little testprogram by Linus out of this thread)
(on a AMD Duron 750)
2.5.52-bk2+sysenter-1 (Brian Gerst):
igor3:~# ./a.out
187.894946 cycles (call 0xfffff000)
299.155075 cycles (int $0x80)
2.5.52-bk6:
igor3:~# ./a.out
202.134535 cycles (call 0xffffe000)
299.117583 cycles (int $0x80)
Not really much, but the difference is there. (I don't about other side
effects)
Christian Leber
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