Messages in this thread | | | Date | Sun, 1 Apr 2012 08:52:35 +0200 | From | Willy Tarreau <> | Subject | Re: [PATCH] x86-32: A better system call mechanism |
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On Sun, Apr 01, 2012 at 08:50:19AM +0200, Willy Tarreau wrote: > Hi Peter, > > On Sun, Apr 01, 2012 at 12:00:00AM +0000, H. Peter Anvin wrote: > > On x86-32, we currently use int $0x80 as the primary system call > > mechanism. Although there are some recent variants available on > > certain hardware (sysenter, syscall) via the vdso, the primary system > > call vector is still way up the interrupt vector table, which is > > inefficient. > > > > This patch adds a very small amount of code which permits the very > > first vector to be used for system call. That vector is #DE, divide > > error, generally known as division by zero. > > Looks like a clever trick, but beyond the beauty, what does it really > save ? Code size is the same as aam 0 / div edx are both 2-byte long, > just like int 0x80. Is the call less expensive ? And if so, how does > it compare to vdso ?
Hmmm I think I just found the response in the Date header, time to get some coffee :-)
Willy
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