Messages in this thread |  | | Date | Tue, 21 May 1996 15:13:34 -0400 (EDT) | From | Ingo Molnar <> | Subject | Re: Proposal: merged system calls |
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On Mon, 20 May 1996, Alan Cox wrote:
> What I'd like to see however is optimising the return path from a syscall. Im > convinced that we could have a "fast return path", and make need_resched, and > signal delivery overwrite the return address on the stack to a slow return > and that it would be a measurable win - Linus, we need to get syscalls down > to 2uS not 3 ;)
current standings in the game of null syscalls contra Linus:
null syscall latency on a Pentium: 221 cycles null syscall latency on an SMP Pentium: 570 cycles :((
(the last 3 cycles score was made by Linus in a pre2.0.4-ish patch to entry.S)
This is the clean CPU latency, with no cache misses or cache misalignments. (can send code on request)
Ingo
ps. [ heh, i tried to optimize entry.S a bit, helped by a silly pentium simulator, and the latency went promptly up to 270 cycles ... Linus, this is no fun, you write too good code :) ]
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