Re: all syscalls initially taking 4usec on a P4? Re: nonblocking UDPv4 recvfrom() taking 4usec @ 3GHz?

From: bert hubert
Date: Tue Feb 20 2007 - 15:45:49 EST

On Tue, Feb 20, 2007 at 02:40:40PM -0500, Benjamin LaHaise wrote:

> Make sure your system is idle. Userspace bloat means that *lots* of idle
> activity occurs in between timer ticks on recent distributions -- all those

You hit the nail on the head. I had previously measured with X shut down,
but the effect didn't disappear.

With init=/bin/bash, recvfrom suddenly takes from 900nsec to 1.3usec, with
only slight correlation between inter-call delay and cycles spent.

I'm investigating this further as it appears this has a real life effect on
my P4 - a drastic one!

processor : 0
vendor_id : GenuineIntel
cpu family : 15
model : 4
model name : Intel(R) Pentium(R) 4 CPU 3.00GHz
stepping : 1
cpu MHz : 3000.131
cache size : 1024 KB
fdiv_bug : no
hlt_bug : no
f00f_bug : no
coma_bug : no
fpu : yes
fpu_exception : yes
cpuid level : 5
wp : yes
flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca
cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe nx
constant_tsc pni monitor ds_cpl cid xtpr
bogomips : 6003.91
clflush size : 64

Thanks for your help!

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