Re: Intel P6 vs P7 system call performance

From: Linus Torvalds (
Date: Thu Dec 19 2002 - 14:37:06 EST

On Thu, 19 Dec 2002 wrote:
> True, but unless I really don't get it, compatibility of a new static
> binary with an old kernel is going to break anyway.


The current code in 2.5.x is perfectly able to be 100% compatible with
binaries even on old kernels. This whole discussion is _totally_
pointless. I solved all the glibc problems early on, and Uli is already
happy with the interfaces, and they work fine for old kernels that don't
have a clue about the new system call interfaces.

WITHOUT any new magic system calls.

WITHOUT any stupid SIGSEGV tricks.

WITHOUT and silly mmap()'s on magic files.

> My point was that the double-mapped page trick adds no overhead in the
> case of a static binary, and just one extra mmap in case of a shared
> binary.

For _zero_ gain. The jump to the library address has to be indirect
anyway, and glibc has several places to put the information without any
mmap's or anything like that.


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