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Thread: "readahead" shortens CD boot time

  1. #1
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    "readahead" shortens CD boot time

    "readahead" shortened KNOPPIX CD boot time by 60sec on our machine (Celeron 2.0 Ghz, 768MB, 24X CD).
    readahead HP http://blog.drinsama.de/erich/en/lin...readahead.html

    "readahead" populates the page cache with data from files so that subsequent reads from these files will not block on disk I/O. /etc/init.d/readahead is a script to cache files which is reburied at KNOPPIX boot process. We made KNOPPIX with readahead to make quick boot on KNOPPIX. The performance is measured by bootchart (http://www.bootchart.org/). The result is shown at the following figures.
    The detail is written in the following HP. iso file of "KNOPPIX wih readahead" is downloadable. You can check performance on your machine. Have fun.
    http://unit.aist.go.jp/itri/knoppix/.../index-en.html

    Target Machine: NotePC Sharp Mebius PC-GP-D7E
    CPU: Celeron 2.0 Ghz, Memory: 768MB, CD Drive: Matsushita DVD-RAM UJ-810

    kernel2.6 + readahead (time: 150sec)

    Original full size figure http://unit.aist.go.jp/itri/knoppix/..._readahead.png

    kernel 2.6 (time: 210sec)

    Original full size figure http://unit.aist.go.jp/itri/knoppix/...tchart-2.6.png

  2. #2
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    Suzaki;

    I downloaded the readahead .iso of Knoppix3.7 and ran it twice to examine the boot time.

    The boot without readahead was 4 minutes and 20 seconds.

    The boot with readahead was 3 minutes and 20 seconds.

    I suggest for completeness that you modify your instructions for booting to include the standard entry....knoppix26...then the readahead and lang=us and myconfig=scan...., etcetra

    The download was a 2 hour download and performs as advertised.

    On the subject of Klik. The atekon.de server seems to be down.

    I would like to try Klik with this download because I think my original Knoppix3.7 has bugs.

    I get USB mixer on this download but not on my original download.

    I am in readahead Knoppix3.7 at this time.

    Good show!

  3. #3
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    I am now running in ...toram.. and haven't yet timed it with and without readahead.

    My system has 3GB of ram athlon 1900+ in knoppix3.7

  4. #4
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    The time to boot with toram stayed constant at 3 minutes and 30 seconds with or without the readahead.

    I didn't expect it to be any different, just verified it. Approx 2 minutes to load the ram files in each case.

  5. #5
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    lilsirecho,

    "readahead" may NOT be effective for "toram" option, because "readahead" bridges gaps with slow device read.

    "readahead" is not effective for small memory PC, because data cached by "readadata" will be got rid of before it is used. I guess 128MB memory is small.

    P.S.
    The KNOPPIX with "readahead" and "bootchart" is brought in the bootchart home page.
    http://www.bootchart.org/samples.html#Knoppix

    P.P.S.
    Google of "knoppix readahead bootchart" was 0 yesterday(2005/01/14).
    It is 2 today(2005/01/15). There are my home page.

  6. #6
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    Suzaki;

    Your system brought to the attention of Klaus Knopper by e-mail. He shows interest. Perhaps you can provide a patch for his review to enhance his understanding of the feature.

    I have hopes the system will provide readahead for DVD installs as well. Klaus plans to release the upcoming version in DVD and CD.

    I would expect that Klaus would include this system in the DVD version only to allow CD users minimum ram if I read your post correctly.

    I would encourage you to apply the same idea to PCLINUXOSv pre8 if you have the time to try it.

    The boot time is longer on that system. It responds to Klik.

    I am disappointed that atekon.de is not reachable. Wanted to test more OS's with klik.

    I previously reported that SFSKNOPPIX performed well with Klik.

    Best to you....

  7. #7
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    The atekon.de wget installed the Klik file.

    I was able to download files of firefox, kaffeine, gcalendar and kwikdisk from the website of berlios.de.

    The downloads from atekon.de are not responding at this time (other than the wget).

    The only source for apps is therefore the berlios.de . It is referenced at the Klik forum.

    I find the klik system to operate correctly in the aist download of Knoppix3.7 in kernel26 with readahead boot utilized.

    I am going to try other OS'es.

  8. #8
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    "readahead" requires much memory

    Dear,

    Thank you, lilsirecho. I'm happy if I can contibute original KNOPPIX.
    But we have to know the effcect of "readahead".

    We check the performance when memory size is changed on our machine(Celeron 2.0 Ghz, 768MB, 24X CD).
    The results is not welcome. The detail is shown at the following URL.
    http://unit.aist.go.jp/itri/knoppix/.../index-en.html

    Memory, kenel2.6, kernel2.6+readahead (minutes:second). Red number means slower case.
    128MB, 7:18, 8:14
    160MB, 4:55, 6:00
    192MB, 4:04, 4:34
    256MB, 3:48, 4:07
    384MB, 3:49, 3:16
    512MB, 3:48, 2:45
    768MB, 3:33, 2:33

    "Normal kernel2.6" with less than 256MB memory was faster than "kernel2.6+readahead". "kernel2.6+readahead" became faster if there was more than 384MB memory.
    However these results don't show the feature of "readahead". The performance depends on the files which are cached by "readahead". In this case we designate most files which is required till KDE

    We have to find the cached files which are suitalbe for memory size.

  9. #9
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    Suzaki;

    Interesting results for the memory sizes. It does put a damper on the idea but perhaps a clue can be derived from examining the effect of cache size.

    My computer is athlon 1900+ and I have 2100Ram with 3GB installed. I am running Knoppix3.7 booted with readahead obtained from your download. I am using Firefox installed through Klik and am running in TORAM mode.

    I have operated Klik in Knoppix3.7, SFSKNOPPIX, PCLinuxOSv7, and PCLinuxOS pre8.

    The server site was down due to too many "hits" and has been slower downloading since coming back on-line.

    Please consider sending "patch" data to Klaus Knopper who expressed interest in the boot method.

    "Googling" reveals other systems utilizing the readahead idea and they may have observations about the effects of ram on the performance.

    One thought....large ram systems use "highmem" which might be enabled early during boot time and would affect the results.

    When loading "TORAM" the time for KDE to load is greatly reduced along with the X params. This suggests that the ram tie-in could affect the CD boot time.

    My system is somewhat slower clock speed than yours and the boot time I reported was about one minute longer than the 150 secs you reported. In fact, the boot time I received was the 210 secs that yours took without readahead.

    This suggests that my large ram slows my boot time since the same program is being loaded on each system.

    The handling of boot cache size might well be worthy of attention.

    Best of luck with your project!

  10. #10
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    Ran a series of readahead tests on 512, 1000,2000, and 3000MB of ram. All timed with lang=us and myconfig=scan using watch timing to Desktop start in KDE(x and KDE very slow in normal boot)

    Readahead with 3GB ram time 3:14
    Normal boot 3GB time 4:11

    Readahead with 2GB ram time3:27

    Readahead with 1GB ram time 3:14

    Readahead with 512MB Ram time 3:12
    Normal boot with 512MB ram time 4:05

    I suggest you use another other computer's operating data for lesser ram which I do not have available.

    It shows that the large X and KDE installs are much improved in loading time.

    Perhaps someone on the net can perform the comparison on a different set of hardware.

    Good luck!

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