Re: Intel P6 vs P7 system call performance

[Linus Torvalds]

On Thu, 19 Dec 2002 [e-mail] 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. 

NO.

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.

		Linus