Re: all syscalls initially taking 4usec on a P4? Re: nonblocking UDPv4 recvfrom() taking 4usec @ 3GHz?
From: Evgeniy Polyakov <hidden>
Date: 2007-02-20 18:49:14
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On Tue, Feb 20, 2007 at 01:42:42PM -0500, Josef Sipek (jsipek@fsl.cs.sunysb.edu) wrote:
A better thing would be to use getuid - it turns into just a return with a memory dereference). I ran it on my 3.06GHz P4 (HT, but only UP kernel), PREEMPT, HZ=1000... 3.290196 0.470588 0.402614 0.396078 0.393464 0.396078 0.386928 0.386928 0.386928 0.386928 0.386928 0.386928 0.386928 0.386928 0.386928 0.386928 0.386928 0.386928 0.386928 0.386928 0.386928 0.386928 0.386928 0.386928 0.386928 0.386928 0.386928 0.386928 0.386928 0.386928 0.386928 0.386928 0.386928 0.386928 0.386928 0.386928 0.386928 0.386928 0.386928 0.386928
I got following. delta for syscall: 9112 cycles = 2.977778 us delta for syscall: 1224 cycles = 0.400000 us delta for syscall: 1071 cycles = 0.350000 us delta for syscall: 1054 cycles = 0.344444 us delta for syscall: 1054 cycles = 0.344444 us Likely first overhead related to cache population or gamma-ray radiation. If it happens only one (it does in my test), then everything is ok I think. Bert, how frequently you get that long recvfrom()? -- Evgeniy Polyakov