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Thread: KDE nearly unresponsive when RAM full and swap is in use

  1. #61
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    Default Re: KDE nearly unresponsive when RAM full and swap is in use

    On 2012-02-01 07:56, sobrus wrote:
    > Workstations you are mentioning were designed for such workloads, both
    > on software and hardware side (SCSI drives, dedicated hardware to
    > offload cpu etc). PCs are not. Maybe that's the problem too.


    No, IMO that is not true. Our PCs outperforms those machines of those days,
    and as I commented, I have used a 32 MiB ram machine with 600 MiB swap,
    with SuSE 7.3, and it worked fine.

    --
    Cheers / Saludos,

    Carlos E. R.
    (from 11.4 x86_64 "Celadon" at Telcontar)

  2. #62
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    Default Re: KDE nearly unresponsive when RAM full and swap is in use

    Maybe it's a problem with HDD performance then.

    CPU performance has increased dramatically, memory performance too, but HDD seek time is still painfully slow (here are no 720000 rpm drives yet )

    Using swap on modern machine puts not only much more small I/O operations on drive (600MB vs 16GB of data to process), but also require them to execute much faster (100Mhz old cpu vs quad core 64-bit monster).

    On modern machines swap should be used for rarely used data, as HDD are simply not fast enough.

    SSD are the way to go, probably paired in RAID. But certain SSD models have some nasty problems with random I/O too, and they have finite number of writes.

    btw. In my opinion, Linux is faster but less resposive than windows.
    Desktop: Intel Q8300@3,3Ghz, 4GB RAM, Foxconn P35A, Sapphire HD5670, OpenSUSE x64
    Server: Via C3@1.4Ghz, 768MB RAM, 8GB Microdrive + OpenSuSE x86
    and other boxes running Windoze

  3. #63

    Default Re: KDE nearly unresponsive when RAM full and swap is in use

    I've been struggling with this problem for a while now. I investigated quite a bit, but eventually just live with it. I'm not doing heavy scientific loads, just a lot of multitasking... The nearly identical Lenovo R400 to my work T400 doesn't have this problem since I upgraded to an SSD. I'm guessing that the increased IOPS helps the random reads and writes of the swapping. I'm curious about some features in kernel 3.2 that might improve the situation. See No-I/O dirty throttling [LWN.net]. Anyone tried it?

  4. #64
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    Default Re: KDE nearly unresponsive when RAM full and swap is in use

    Am 01.02.2012 20:56, schrieb adler187:
    >
    > I'm curious about some features in kernel
    > 3.2 that might improve the situation. See 'No-I/O dirty throttling
    > [LWN.net]' (http://lwn.net/Articles/456904/). Anyone tried it?
    >

    I did not see that before, thanks for the link, I will check this over
    the weekend. Thanks for sharing here.


    --
    PC: oS 11.4 (dual boot 12.1) 64 bit | Intel Core i7-2600@3.40GHz | KDE
    4.6.0 | GeForce GT 420 | 16GB Ram
    Eee PC 1201n: oS 11.4 64 bit | Intel Atom 330@1.60GHz | KDE 4.8.0 |
    nVidia ION | 3GB Ram

  5. #65
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    Default Re: KDE nearly unresponsive when RAM full and swap is in use

    On 2012-02-01 14:46, sobrus wrote:

    > On modern machines swap should be used for rarely used data, as HDD are
    > simply not fast enough.


    They are much faster than they were. Possibly the reason is that this
    situation is not tested by devs, they have powerful machines.

    One way to improve the situation if you have several hard disks is to put
    one swap on each with the same priority. The kernel should distribute the
    i/o in parallel.

    --
    Cheers / Saludos,

    Carlos E. R.
    (from 11.4 x86_64 "Celadon" at Telcontar)

  6. #66

    Default Re: KDE nearly unresponsive when RAM full and swap is in use

    Quote Originally Posted by robin_listas View Post
    On 2012-01-31 04:15, JoergJaeger wrote:
    > On 30.01.2012 05:08, Carlos E. R. wrote:
    >> On 2012-01-30 13:06, sobrus wrote:
    >>>
    >>> Try kernel feature called "zram". Five minutes of work (few commands in

    ....
    >> A two level swap. I wonder.

    >
    > If i understand that correct you reserve space in ram to swap it in ram
    > versus on the hdd.
    >
    > It still doesn't explain why a computer runs slow with a particular
    > application.


    The OP hasn't tried zram yet. I'm interested in the result.
    I'm going to give this a try when I get a chance (I'm a bit busy now). I'll update the thread when I get to it. In the long term, I think I've settled on getting a small SSD for my desktop. I can then save the more laborious tasks for the desktop, and be sure to expect a big wait when loading 8GB datasets into my laptop. Sometimes it's difficult to throttle your lust for new hardware, but it would be silly to go nuts here. It's not worth spending $300 to speed up something I do once a week.

  7. #67
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    Default Re: KDE nearly unresponsive when RAM full and swap is in use

    Robin, they are, but not at random operations. And swap access is almost exclusively random.

    Look
    Let's say you have three machines
    1) Amiga 3000, MC68030 25Mhz, 4MB RAM and Quantum LPS420A 420MB HDD.
    http://www.hdtune.com/results/Quantum_LPS420A.gif
    Access time ~22.7ms, CPU MIPS ~8 (!).

    2) Pentium 100 with 16MB RAM and Fujitsu 6GB HDD
    http://www.hdtune.com/results/Fujitsu_MPE3064AT.gif
    This CPU has ~188MIPS and Fujitsu access time is ...15.3 ms

    3) Now take modern Core i7 2600K, it has 128.000 MIPS and newest biggest 1TB per platter expensive state-of-the-art 3TB Barracuda XT:
    http://hdd-compare.com/userfiles/ima...0651as-3tb.png
    which has 17ms access time(!!!).

    Core i7 2600 is (in general) about 16.000 times faster than Motorola 030 in expensive $3300 Amiga 3000 workstation from 1990.
    But HDD Access time is the same.
    OK, even if it was 10 times better - still it's not quite enough to feed Core i7 with data. It wastes much more time seeking data than actually reading it.

    Traditional mechanical disks are no longer enough. SSD is the only way to go.
    Desktop: Intel Q8300@3,3Ghz, 4GB RAM, Foxconn P35A, Sapphire HD5670, OpenSUSE x64
    Server: Via C3@1.4Ghz, 768MB RAM, 8GB Microdrive + OpenSuSE x86
    and other boxes running Windoze

  8. #68
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    Default Re: KDE nearly unresponsive when RAM full and swap is in use

    On 02/02/2012 02:56 AM, lazlojamf wrote:
    > It's not worth spending $300 to speed up something I do once a
    > week.


    especially if you ponder: Patience is a virtue.

    --
    DD
    Read what Distro Watch writes: http://tinyurl.com/SUSEonDW

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