Messages in this thread | | | Date | Sun, 20 Sep 2009 17:22:20 -0700 | From | "Justin P. Mattock" <> | Subject | Re: Poor desktop responsiveness with background I/O-operations |
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Mike Galbraith wrote: > On Sun, 2009-09-20 at 10:50 +0200, Ulrich Lukas wrote: > >> Arjan van de Ven wrote: >> >>> can you try the following two things? >>> >>> echo 4096> /sys/block/sda/queue/nr_requests >>> for i in `pidof kjournald` ; do ionice -c1 -p $i ; done >>> >> I tried this just now, but it doesn't change things much. I can do a >> more testing later today. >> > > Try ionice -c3 for your dd. > > >>> I assume you're using CFQ. >>> >> Yes, it's CFQ. (see .config of my previous posting) >> >> Filesystem is EXT4. >> > > Mine is ext3. > > I can easily reproduce pain. The attached cheezy test script, when run > back to back with no args (stock IO), regularly produces beauties: > > Performance counter stats for 'sh -c konsole -e exit': > > 257.670601 task-clock-msecs # 0.004 CPUs > 1036 context-switches # 0.004 M/sec > 30 CPU-migrations # 0.000 M/sec > 6317 page-faults # 0.025 M/sec > 471734719 cycles # 1830.767 M/sec > 393365060 instructions # 0.834 IPC > 7849464 cache-references # 30.463 M/sec > 1038976 cache-misses # 4.032 M/sec > > 65.766937233 seconds time elapsed > > Yup, a full minute to get a binary loaded and fired up. Seems it and > others get evicted by the VM. Getting whatever back into ram is painful > to listen to (poor disk/me.. seek latency eating MUCH time). > > Calling script back to back with args 1 (realtime foreground) 3 (idle > background) does best: > > Performance counter stats for 'sh -c konsole -e exit': > > 169.915036 task-clock-msecs # 0.077 CPUs > 439 context-switches # 0.003 M/sec > 9 CPU-migrations # 0.000 M/sec > 6314 page-faults # 0.037 M/sec > 363128252 cycles # 2137.117 M/sec > 367410945 instructions # 1.012 IPC > 5822302 cache-references # 34.266 M/sec > 437189 cache-misses # 2.573 M/sec > > 2.213079979 seconds time elapsed > > Args 2 (best effort foreground) and 3 (idle background); > > Performance counter stats for 'sh -c konsole -e exit': > > 176.689856 task-clock-msecs # 0.015 CPUs > 357 context-switches # 0.002 M/sec > 15 CPU-migrations # 0.000 M/sec > 6314 page-faults # 0.036 M/sec > 374861947 cycles # 2121.582 M/sec > 368929476 instructions # 0.984 IPC > 5806286 cache-references # 32.861 M/sec > 496651 cache-misses # 2.811 M/sec > > 12.036165968 seconds time elapsed > > -Mike > Wow, at first I did not notice anything from your *.sh script, but then a few moments later, the system became vary sluggish. firefox takes about 15 seconds to load. OS is mint linux with the latest HEAD on an imac9,1.
Justin P. Mattock
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