Date: Mon, 17 Sep 2001 02:09:34 +0200 (CEST) From: Cyrille Lefevre <clefevre@citeweb.net> To: Erik Trulsson <ertr1013@student.uu.se> Cc: stable@FreeBSD.ORG Subject: Re: make -j4 vs -j8... 4 works, but 8 does not Message-ID: <200109170009.f8H09Y921584@gits.dyndns.org> In-Reply-To: <20010916003359.A48953@student.uu.se>
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Erik Trulsson wrote: > On Sat, Sep 15, 2001 at 06:06:10PM -0400, Garance A Drosihn wrote: > > > [aside on those multiple builds that I did: It was interesting that > > even though it was on a dual-processor system, there was not much of > > a speed improvement (on 4.3-stable) when going from -j4 to -j10. Big > > improvement going from -j1 to -j4, but after that it didn't help much] > > That sounds exactly like what I would expect. More than 2 (or maybe 3) > jobs per CPU is normally not going to make things go faster but might > actually slow it down. I'm not right w/ you. let's try : # setup a reusable environment cd /sys/compile/MYKERNEL make depend make # run the jobs for i in 1 2 4 8; do (date;touch opt_global.h;time make -j$i all;date) >| .j$i 2>&1 done results are (on my old P200 processor) : j1 12:36 j2 12:46 j4 11:36 j8 11:21 so, for a 12 min job, you could win 1 min using -j4, which may gives you 1 hour for a 12 hours job (such as buildworld :). ok, it's not so many, but that may help a lot. for instace, I currently use -j4 since -j8 is too CPU and memory intensive (the machine slow down significally). PS : I'm using SCSI disks. using IDE disks probably gives you different results. I/O are very differents between the two. Cyrille. -- Cyrille Lefevre mailto:clefevre@citeweb.net To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-stable" in the body of the message
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