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DateThu, 19 Dec 2002 14:26:38 -0800
From"H. Peter Anvin" <>
SubjectRe: Intel P6 vs P7 system call performance
Digg This
Linus Torvalds wrote:

Uli's suggested glibc approach is to just put the magis system call address (which glibc gets from the AT_SYSINFO elf aux table entry) into the per-thread TLS area, which is alway spointed to by %gs anyway.
THIS WORKS WITH ALL DSO'S WITHOUT ANY GAMES, ANY MMAP'S, ANY RELINKING, OR ANY EXTRA WORK AT ALL!

The system call entry becomes a simple

call *%gs:constant-offset

Not mmap. No magic system calls. No relinking. Not _nothing_. One instruction, that's it.


Unfortunately it means taking an indirect call cost for every invocation...
-hpa

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