Messages in this thread | | | Date | Wed, 4 Oct 2000 17:11:46 +0200 | From | "Andi Kleen" <> | Subject | Re: wasting time on page fault |
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On Wed, Oct 04, 2000 at 11:00:41AM -0400, Brian Gerst wrote: > 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.
You don't need to preserve any registers which are not %eax, they are already saved. There are tons of ways to do it via the stack or with a temporary register.
-Andi
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