Messages in this thread | | | Date | Mon, 15 Jun 2009 13:04:02 -0700 (PDT) | From | Linus Torvalds <> | Subject | Re: [tip:perfcounters/core] perf_counter: x86: Fix call-chain support to use NMI-safe methods |
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On Mon, 15 Jun 2009, Ingo Molnar wrote: > > Well i guess it depends. For server apps it is true - syscalls are a > lot more dominant, MMs are long-running so any startup cost gets > amortized and pagefaults are avoided. > > For something like a kernel build we have 7 times as many pagefaults > as syscalls:
Ingo - calm down.
This is not about page faults.
This is purely about taps FROM KERNEL SPACE.
Yes, for the kernel build we have 7 times as many page faults as system calls, BUT I BET 99.9% of them are from user mode!
The whole "open-code iret" only works for exceptions that happened in kernel mode. That's a _vanishingly_ small number (outside of device interrupts that happen during idle).
Linus
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