Re: Intel P6 vs P7 system call performance

From: H. Peter Anvin (hpa@transmeta.com)
Date: Wed Dec 18 2002 - 15:14:14 EST


Terje Eggestad wrote:
> what about:
>
> int (*_vsyscall) (int, ...);
> _vsyscall = mmap(NULL, getpagesize(), PROT_READ|PROT_EXEC,
> MAP_VSYSCALL, , );
>
> or if you're afraid of running out of MAP_* flags:
>
> fd = open("/dev/vsyscall", );
> _vsyscall = mmap(NULL, getpagesize(), PROT_READ|PROT_EXEC, MAP_SHARED,
> fd, 0);
>
> Then you can leisurely map it in just after the programs text segment.
>

Very ugly -- then the application has to do indirect calls.

        -hpa

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