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Date: Fri, 25 Jan 2008 12:32:56 +0100 From: Asbjorn Sannes <asbjorsa@....uio.no> To: Linux Kernel Mailing List <linux-kernel@...r.kernel.org> Subject: Unpredictable performance Hi, I am experiencing unpredictable results with the following test without other processes running (exception is udev, I believe): cd /usr/src/test tar -jxf ../linux-2.6.22.12 cp ../working-config linux-2.6.22.12/.config cd linux-2.6.22.12 make oldconfig time make -j3 > /dev/null # This is what I note down as a "test" result cd /usr/src ; umount /usr/src/test ; mkfs.ext3 /dev/cc/test and then reboot The kernel is booted with the parameter mem=81920000 For 2.6.23.14 the results vary from (real time) 33m30.551s to 45m32.703s (30 runs) For 2.6.23.14 with nop i/o scheduler from 29m8.827s to 55m36.744s (24 runs) For 2.6.22.14 also varied a lot.. but, lost results :( For 2.6.20.21 only vary from 34m32.054s to 38m1.928s (10 runs) Any idea of what can cause this? I have tried to make the runs as equal as possible, rebooting between each run.. i/o scheduler is cfq as default. sys and user time only varies a couple of seconds.. and the order of when it is "fast" and when it is "slow" is completly random, but it seems that the results are mostly concentrated around the mean. -- Asbjørn Sannes -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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