Re: Differences between FreeBSD and Linux system call mechanism

Alan Cox (alan@lxorguk.ukuu.org.uk)
Thu, 3 Sep 1998 14:47:10 +0100 (BST)


> > required. The FreeBSD mechanism for kernel entry (and subsequet
> > context switch) is threfore more efficient than that used by Linux.
>
> I'm starting to wonder. Terry normally knows what he is talking about,

I was under the impression he just used big words and prayed 8)

> 1) Linux system calls are done using software interrupt 0x80 on ia32.
> Does this qualify as a "call-gate based kernel entry"?

No. Call gates are a paticular intel mechanism for jumping between rings
(priviledge levels). You can see an example of this in the iBCS2 handlers
since iBCS uses call gates. An int based call is faster, and sysenter
is potentially faster still but sysenter is only on some later PII chips

> 3) I'm not sure about Terrys definition of "efficient", but if he means
> required CPU cycles I thought that there were not that many left in
> Linux that FreeBSD could be better. Has anybody hard numbers for both
> kernels?

lmbench is your friend. Im sure Larry McVoy can provide

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