Results 1 to 6 of 6

Thread: Knoppix 6.4.4 sg(x) performance

  1. #1
    Junior Member registered user
    Join Date
    Oct 2007
    Posts
    29

    Knoppix 6.4.4 sg(x) performance

    I realise this is not a knoppix problem, just hoping for frendly pointers and direction.

    I have updated to knoppix 6.4.4 with kernel 2.6.37 and I have discovered a big problem for me with testing scsi hard drives using the sg(x) driver, compared to Knoppix 6.0 with a 2.6.28.4 kernel.
    Just one of the many ways I have found to use knoppix, is as a scsi hard drive test environment. I have been using knoppix with kernel 2.6.28.4 for a number of years very sucessfuly.

    I commonly test 14 scsi drives simultaneously in an external drive bay using for example scsi write-same "erase" command. Although we use a product from santools, smartmon-ux, sg_write_same is available form scsitools etc. The performance from this new kernel makes the test operation impractical.

    Although, I can test one drive at a time under 2.6.37 with the same test time as 2.6.28.4, as soon as I load additional drives the test times sore from 18m to 134m. To make clear this does not happen under 2.6.28.4, and the write-same command takes very little I/O overhead.

    I have tried googling and come across I/O throttling. Am I on the right lines?
    I have attempted to research cgroups but the info is mainly on limiting throughput.
    I have posted on the linux kernel mailing list, those guys are very, very busy.
    Any ideas would be appreciated, happy to run any tests etc. Many reasons why I would like to keep 2.6.37.

    Regards,

    Will

  2. #2
    Senior Member
    Join Date
    Jan 2011
    Posts
    242
    Hi willbrown,

    What makes you think this is not a Knoppix problem ? Knoppix is a mixture of packages from different Debian repositories. Anything not 'desktop' is likely to have had less test coverage. You may just be using a bunch of packages that are not totally compatible but I guess you know that already.

    You're using scsitools. That is a user space package with no kernel module dependencies ? (unlike open-scsi for example). It's not on my 6.4.4 so I guess you installed it yourself. Did you get the 0.10.2.1 version from the squeeze repository or the 0.12.02 version from the sid repository ?

    Have you tried using time to figure out whether the excessive time is kernel space CPU, user space CPU or wait time ?

    Have you checked the Debian BTS to see if your problem is (was) a known problem (that has been fixed) ? Do you know if there is an upstream ? I can't find one.

    Posting a question on the Linux kernel mailing list for what, at first glance, is not a kernel issue will just get you ignored. Why not try a Debian mailing list ? debian-knoppix@lists.debian.org perhaps. Keep your question short and specific else you risk a vague reply after a long pause.

    Left-of-centre suggestion: have you tried running the 64-bit kernel ?

  3. #3
    Junior Member registered user
    Join Date
    Oct 2007
    Posts
    29
    Hello Forester,

    Thanks for your input.

    You are quite correct, I don't know it's a kernel problem. My own attempts to find a resolution to this, merely pointed me in this direction. Hence, my post here to prevent this potential dead-end. Probably my poor wording.

    For example:
    Code:
    With htop & top I can see the following while running write-same * 14 drives:
                           2.6.28.4                     2.6.37 
    Cpu (user)        4.6%                           0.7%
    Cpu (system)   8.5%                           1.5%
    Load Avg           0.68                         12.97
    All dynamic figures of course.
     
    Something appears to be stopping the cpu’s from doing any work, yet the overall load is up!
    Htop - 2.6.37 shows cpu1 @ approx 1 to 2% & cpu2 is doing nothing, fixed at a solid 0.0%.
    Htop - 2.6.28.4 cpu1 @ 13.6% cpu2 @ 11.8%
    All memory stats appear the same between the two kernels
    I indeed added scsitools to my remastered image and it is 0.10-2.1, squeeze.

    Just trying 64 bit but it does not see any scsi drives, only ide, I guess no 64 bit drivers on the build.

    Will try time and the mailing list tips you have suggested.

    Regards

    Will

  4. #4
    Senior Member
    Join Date
    Jan 2011
    Posts
    242
    Hmm ... I've heard the 64-bit support is a bit limited on the CD edition. I have the MAXI (DVD) edition and it appears to have a full set of drivers.

    I'd be interested in what top reports on the third row for wa, hi, si. All are normally 0 but I expect you've got a large number for wa (waiting on I/O). A large number in either of the other two would be bad news indeed.

    The calculation of loadavg is odd. According to the Wikipedia entry for Load Average:

    An idle computer has a load number of 0 and each process using or waiting for CPU (the ready queue or run queue) increments the load number by 1. Most UNIX systems count only processes in the running (on CPU) or runnable (waiting for CPU) states. However, Linux also includes processes in uninterruptible sleep states (usually waiting for disk activity), which can lead to markedly different results if many processes remain blocked in I/O due to a busy or stalled I/O system. This, for example, includes processes blocking due to an NFS server failure or to slow media (e.g., USB 1.x storage devices). Such circumstances can result in an elevated load average, which does not reflect an actual increase in CPU use (but still gives an idea on how long users have to wait).
    This sounds like your problem.

    Here's another left-of-centre suggestion. Do you have a IDE drive or the flash disk drive in your system at all ? With the older 2.6.28.4 kernel, do such drives still have the hda, hdb designation ? At some point in the last few years, folks have switched so all disc drives, not just SCSI drives, use the sda, sdb, ... designation. An old script that assumed sdx was SCSI might start asking questions of a non-SCSI disk the drive can't answer and perhaps your problem is low level software waiting for responses that never come. I remember when 'untu first switched there was a cock-up that meant some laptop (including mine) never got a response adding an unwelcome 90 second delay at boot time.

  5. #5
    Junior Member registered user
    Join Date
    Oct 2007
    Posts
    29
    Hi Forester,

    Sorry for the delay.

    Thanks for the reply. As an aside, due to your input, I have built a 64bit knoppix644 CD. I just did'nt realise the remaining 64 bit deivers were only on the DVD version. So thanks for that.

    Back to the scsi problem, the wa is firmly fixed at 0.0%.

    2.6.37 - Via top i get these figures:
    Cpu(s)
    between 0.5 to 2.1%us
    between 0.8 to 1.3%sy
    0.0%ni
    between 96.7 to 98.3%id
    0.0%wa
    0.0%hi
    0.0%si
    0.0%st
    Avg Load varies but is made up of 3 figures, typically they would be:
    12.06 10.48 5.89

    #########

    And to confirm, 2.6.28.4 - Via top i get these figures:
    Cpu(s)
    between 1.5 to 2.1%us
    between 2.6 to 4.6%sy
    0.0%ni
    between 89.4.7 to 98.2%id
    0.0%wa
    0.0%hi
    0.0%si
    0.0%st
    Avg Load , typically they would be:
    0.23 0.27 0.12

    Very Strange...

    I have no ide devices installed but with this kernel they are seen as sda not hda etc.

    Regards,

    Will

  6. #6
    Senior Member
    Join Date
    Jan 2011
    Posts
    242
    Hi WillBrown,

    The figures show the kernel isn't blocked and your program isn't waiting on disk i/o.

    If you look up the definitions of load average it is, roughly, a measure of how many processes are queued up waiting for the CPU but on some systems (and Knoppix/Linux may be one of these), it is the number of threads waiting to use the CPU. If sg_write_same creates a thread for each of the 14 disks and then each thread takes some semaphore around some critical operation, then 13 threads will be waiting. Looks like each thread takes the semaphore for a long time, instead of a short one. Looks like a bug in sg_write_same but that is, of course, speculation.

    On Knoppix 6.4.4, the packages of interest are:

    Code:
    sg3-utils      1.29-1
    libsgutils-2-2 1.29-1
    BTW, scsitools is a different package - you had me confused for a while there.

    Can you have a look to see what versions of these you have with your older Knoppix ? I suggest open a terminal and use grep to filter the output of dpkg -l.

    There are no bug reports against either package in either the Debian or Ubuntu bug trackers.
    The project home page is here:

    Code:
    http://freshmeat.net/projects/sg3_utils/
    There's no bug list and to report a problem you need to register. There is also:

    Code:
    http://sg.danny.cz/sg/index.html
    that looks like the author's home page but it too is hosted on freshmeat.net (?) and the author is Douglas Gilbert, which doesn't sound terribly Czech. There is a mailto: for him there. On the project site, my guess is he is dpgilbert.

    The only other thing I can suggest is that one or other of these sites has .deb files for both packages for versions old and new. You might try some of these (on old and new Knoppix) to see if you can find out when the problem was introduced.

    Either way, I think you are going to have to contact the author. Sorry I could not help you solve this on your own.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  


A-Tech 8GB DDR3 1600 PC3-12800 Laptop SODIMM 204-Pin Memory RAM PC3L DDR3L 1x 8G picture

A-Tech 8GB DDR3 1600 PC3-12800 Laptop SODIMM 204-Pin Memory RAM PC3L DDR3L 1x 8G

$13.99



HyperX FURY RAM DDR4 16GB 8GB 32GB 4GB 3200 2666 2400 2133 Desktop Memory DIMM picture

HyperX FURY RAM DDR4 16GB 8GB 32GB 4GB 3200 2666 2400 2133 Desktop Memory DIMM

$9.64



A-Tech 16GB 2 x 8GB PC3-12800 Laptop SODIMM DDR3 1600 Memory RAM PC3L 16G DDR3L picture

A-Tech 16GB 2 x 8GB PC3-12800 Laptop SODIMM DDR3 1600 Memory RAM PC3L 16G DDR3L

$27.98



CRUCIAL DDR3L 8GB 16GB 32GB 1600 MHz PC3-12800 Laptop Memory RAM SODIMM 204-Pin picture

CRUCIAL DDR3L 8GB 16GB 32GB 1600 MHz PC3-12800 Laptop Memory RAM SODIMM 204-Pin

$14.35



A-Tech 8GB PC3-12800 Desktop DDR3 1600 MHz Non ECC 240-Pin DIMM Memory RAM 1x 8G picture

A-Tech 8GB PC3-12800 Desktop DDR3 1600 MHz Non ECC 240-Pin DIMM Memory RAM 1x 8G

$13.99



Team T-FORCE VULCAN Z 16GB (2 x 8GB) 288-Pin PC RAM DDR4 3200 (PC4 25600) Intel picture

Team T-FORCE VULCAN Z 16GB (2 x 8GB) 288-Pin PC RAM DDR4 3200 (PC4 25600) Intel

$35.99



Crucial CT16G4SFD824A 16GB DDR4-2400 (PC4-19200) Memory Module picture

Crucial CT16G4SFD824A 16GB DDR4-2400 (PC4-19200) Memory Module

$25.00



Kingston HyperX FURY DDR3 8GB 16GB 32G 1600 1866 1333 Desktop Memory RAM DIMM picture

Kingston HyperX FURY DDR3 8GB 16GB 32G 1600 1866 1333 Desktop Memory RAM DIMM

$13.25



Hynix 64GB 4Rx4 PC4-2133P-L LRDIMM DDR4-17000 ECC Load Reduced Server Memory RAM picture

Hynix 64GB 4Rx4 PC4-2133P-L LRDIMM DDR4-17000 ECC Load Reduced Server Memory RAM

$64.99



A-Tech 32GB 2x 16GB PC4-25600 Laptop SODIMM DDR4 3200 MHz Non-ECC Memory RAM 32G picture

A-Tech 32GB 2x 16GB PC4-25600 Laptop SODIMM DDR4 3200 MHz Non-ECC Memory RAM 32G

$59.99