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Date: Tue, 20 Feb 2007 21:45:05 +0100 From: bert hubert <bert.hubert@...herlabs.nl> To: Benjamin LaHaise <bcrl@...ck.org> Cc: Evgeniy Polyakov <johnpol@....mipt.ru>, Josef Sipek <jsipek@....cs.sunysb.edu>, Andi Kleen <andi@...stfloor.org>, netdev@...r.kernel.org, linux-kernel@...r.kernel.org Subject: Re: all syscalls initially taking 4usec on a P4? Re: nonblocking UDPv4 recvfrom() taking 4usec @ 3GHz? 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! -- http://www.PowerDNS.com Open source, database driven DNS Software http://netherlabs.nl Open and Closed source services - To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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