From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stephen Hemminger Subject: Re: all syscalls initially taking 4usec on a P4? Re: nonblocking UDPv4 recvfrom() taking 4usec @ 3GHz? Date: Tue, 20 Feb 2007 13:02:26 -0800 Message-ID: <20070220130226.7fb80d20@freekitty> References: <20070219231447.GA4400@outpost.ds9a.nl> <20070220162714.GA3245@outpost.ds9a.nl> <20070220164124.GA24930@2ka.mipt.ru> <20070220184242.GA30077@filer.fsl.cs.sunysb.edu> <20070220184859.GA1949@2ka.mipt.ru> <20070220193319.GA8800@outpost.ds9a.nl> <20070220194040.GA18976@kvack.org> <20070220204505.GB8800@outpost.ds9a.nl> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Cc: Benjamin LaHaise , Evgeniy Polyakov , Josef Sipek , Andi Kleen , netdev@vger.kernel.org, linux-kernel@vger.kernel.org To: bert hubert Return-path: Received: from smtp.osdl.org ([65.172.181.24]:48955 "EHLO smtp.osdl.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1030388AbXBTVC5 (ORCPT ); Tue, 20 Feb 2007 16:02:57 -0500 In-Reply-To: <20070220204505.GB8800@outpost.ds9a.nl> Sender: netdev-owner@vger.kernel.org List-Id: netdev.vger.kernel.org On Tue, 20 Feb 2007 21:45:05 +0100 bert hubert wrote: > 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! > What happens with preempt if your process is high priority or SCHED_FIFO/SCHED_RR? -- Stephen Hemminger