From mboxrd@z Thu Jan 1 00:00:00 1970 From: Prarit Bhargava Date: Fri, 27 Jan 2006 22:08:43 +0000 Subject: Re: boot-time slowdown for measure_migration_cost Message-Id: <43DA99EB.6020909@sgi.com> List-Id: References: In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: "Luck, Tony" Cc: Bjorn Helgaas , Ingo Molnar , linux-ia64@vger.kernel.org, linux-kernel@vger.kernel.org Luck, Tony wrote: >>The boot-time migration cost auto-tuning stuff seems to have >>been merged to Linus' tree since 2.6.15. On little one- or >>two-processor systems, the time required to measure the >>migration costs isn't very noticeable, but by the time we >>get to even a four-processor ia64 box, it adds about >>30 seconds to the boot time, which seems like a lot. > > > I only see about 16 seconds for a 4-way tiger (not that 16 seconds > is good ... but it not as bad as 30). This was with a build > from tiger_defconfig that sets CONFIG_NR_CPUS=4 ... so I wonder > what's causing the factor of two. I measured with a printk > each side of build_sched_domains() and booted with the "time" > command line arg to get: I've noticed the delay on a 16p and 64p. At first I thought it was a system hang but have since learned to live with the delay. What happens on a 512 cpu > Altix (if it's quadratic, they may be still waiting for the > boot to finish :-) Not quadratic. This is a 64p Altix ... [ 9.942253] Brought up 64 CPUs [ 9.942904] Total of 64 processors activated (143654.91 BogoMIPS). [ 9.943995] build_sched_domains: start [ 32.108439] migration_cost=0,32232,39021 [ 37.894391] build_sched_domains: end P. > > -Tony > - > To unsubscribe from this list: send the line "unsubscribe linux-ia64" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html >