Date: Tue, 13 Feb 2001 11:55:24 -0800 From: Kent Stewart <kstewart@urx.com> To: void <float@firedrake.org> Cc: Jordan Hubbard <jkh@winston.osd.bsdi.com>, Danny Braniss <danny@cs.huji.ac.il>, freebsd-hackers@FreeBSD.ORG Subject: Re: soft updates performance Message-ID: <3A89912C.646DC42B@urx.com> References: <kstewart@urx.com> <81045.982046200@winston.osd.bsdi.com> <20010213191659.A5429@firedrake.org>
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void wrote: > > On Mon, Feb 12, 2001 at 10:36:40PM -0800, Jordan Hubbard wrote: > > > > With how many running processors? If you're running -j4 on a > > uniprocessor system, you're only introducing competition for already > > scarce CPU resources, though -j2 can be a speedup since this allows > > one target build to run while another is in an I/O wait. I've only > > seen a speedup with -j4 when using at least 2 CPUs. > > Interesting. When I asked about optimal values on this list maybe a > year ago, I was told that -j(4 * NCPU) was a good choice. I guess that > doesn't work for NCPU == 1. I did some testing last night and found that there was a difference of 50% between -j4 and not running softupdates and running softupdates and no -j4. The buildworld elapsed clock times were 58 minutes for the first case and 38 minutes for the last case. Even -j2 added 11 minutes to the elapsed build time. I thought I had been hit by one of the file system cron jobs on -j2 and ran it again. The difference was around 10 seconds between the two runs. The user time isn't that much different but the -jn contention really slows the buildworld down. The times are in a table at http://dsl1-160.dynacom.net/freebsd/urban_legends.html kent > > -- > Ben > > "I told Paddy no, I told Steve no, I told Paul no, and Ben fell asleep." > --Kate C. (no, different Ben, I would have stayed up) -- Kent Stewart Richland, WA mailto:kbstew99@hotmail.com http://kstewart.urx.com/kstewart/index.html FreeBSD News http://daily.daemonnews.org/ To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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