Re: [PATCH] x86-64: espfix for 64-bit mode *PROTOTYPE*

H. Peter Anvin
2014-04-22T01:15:43Z

I wanted to avoid the "another cpu made this allocation, now I have to free" crap, but I also didn't want to grab the lock if there was no work needed.

On April 21, 2014 6:06:19 PM PDT, Andrew Lutomirski <amluto@gmail.com> wrote:
>On Mon, Apr 21, 2014 at 5:53 PM, H. Peter Anvin <hpa@zytor.com> wrote:
>> Well, if 2^17 CPUs are allocated we might 2K pages allocated. We
>could easily do a bitmap here, of course. NR_CPUS/64 is a small
>number, and would reduce the code complexity.
>>
>
>Even simpler: just get rid of the check entirely. That is, break out
>of the higher level loops once one of them is set (this should be a
>big speedup regardless) and don't allocate the page if the first PTE
>is already pointing at something.
>
>After all, espfix_already_there is mostly a duplicate of
>init_espfix_cpu.
>
>--Andy

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