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SubjectRe: wasting time on page fault
Mikulas Patocka wrote:
>
> Hi.
>
> arch/i386/kernel/entry.S
> xchgl %eax, ORIG_EAX(%esp) # orig_eax (get the error code. )
> movl %esp,%edx
> xchgl %ecx, ES(%esp) # get the address and save es.
> pushl %eax # push the error code
>
> xchg with memory operand has implicit lock prefix and is slooooooow. It is
> really bad idea to have it in page fault handler.

Thank the small register set of the x86 for this. If you can come up
with a way to do it in fewer cycles and preserve all the registers and
stack layout, your input is welcome.

--

Brian Gerst
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