Date: Wed, 7 May 2003 22:03:54 -0500 From: Dan Nelson <dnelson@allantgroup.com> To: Andre Guibert de Bruet <andy@siliconlandmark.com> Cc: current@freebsd.org Subject: Re: High CPU utilization even with DMA enabled? Message-ID: <20030508030354.GD31032@dan.emsphone.com> In-Reply-To: <20030507181628.J30571@alpha.siliconlandmark.com> References: <20030507181628.J30571@alpha.siliconlandmark.com>
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In the last episode (May 07), Andre Guibert de Bruet said: > Here's the output of top while moving a large file from one disk to > another on my otherwise idle desktop machine: > > PID USERNAME PRI NICE SIZE RES STATE C TIME WCPU CPU COMMAND > 26 root -68 -187 0K 12K WAIT 0 141:36 79.98% 79.98% irq7: dc0 ohci0 Is this line truncated? If not, your CPU load is caused by either your network card or your USB interface, not your file copy. > 24 root -64 -183 0K 12K WAIT 0 0:27 1.22% 1.22% irq15: ata1 > Now, I realize that copying a file from one disk to another requires cpu > cycles even with DMA enabled, but is 80% of cpu usage to be expected? > Also, wouldn't one expect process id 24 (irq15: ata1) to be using CPU > during such transfers? It is; I'd even call 1.22% cpu load a bit high, although I have no IDE systems to compare it against. All it's doing is DMA'ing data. -- Dan Nelson dnelson@allantgroup.com
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