Results 1 to 4 of 4
  1. #1
    Join Date
    May 2005
    Location
    Paris
    Posts
    46

    Unanswered: How to set up max IO size on RHEL 4.0 ?

    hi all,

    platform is RHEL 4.0.
    Description of the issue: With RH AS 2.1,
    it was advised to set up fs.aio-max-size up to 1048576 to speed up 'create database' statement.
    With RH AS 4.0, setting up this key is not allowed?
    I get following output when trying to set it:

    [root etc]# /sbin/sysctl -p
    net.ipv4.ip_forward = 0 net.ipv4.conf.default.rp_filter = 1
    net.ipv4.conf.default.accept_source_route = 0
    kernel.sysrq = 0 kernel.core_uses_pid = 1
    kernel.shmmax = 2392492032

    error: 'fs.aio-max-size' is an unknown key

    Thus, the IO size observed (with iostat) when creating a database is limited to the default of 128K.

    My questions are :
    1. How to set up max IO size on RHEL 4.0,
    2. If fs.aio-max-size does not work anymore, what is the equivalent of fs.aio-max-sizefor RHEL 4.0?

    My configuration is:

    RHEL 4.0 $ uname -a
    Linux 2.6.9-5.ELsmp #1 SMP i686 i686 i386 GNU/Linux
    $ rpm -q glibc glibc-2.3.4-2
    $ dataserver -v Adaptive Server Enterprise/12.5.3/EBF 12876 ESD#4/P/Linux Intel/Enterprise Linux/ase1253/1923/32-bit/OPT/Thu Sep 8 06:16:18 2005


    With my firsts searchs, i think there is something to do here but i am not sure :

    /proc/sys/fs

    [root@ fs]# ll
    total 0
    -rw-r--r-- 1 root root 0 Nov 15 18:42 aio-max-nr
    -r--r--r-- 1 root root 0 Nov 15 18:42 aio-nr
    drwxr-xr-x 1 root root 0 Nov 8 10:49 binfmt_misc
    -r--r--r-- 1 root root 0 Nov 15 18:42 dentry-state
    -rw-r--r-- 1 root root 0 Nov 15 18:42 dir-notify-enable
    -rw-r--r-- 1 root root 0 Nov 15 18:42 file-max
    -r--r--r-- 1 root root 0 Nov 15 18:42 file-nr
    -r--r--r-- 1 root root 0 Nov 15 18:42 inode-nr
    -r--r--r-- 1 root root 0 Nov 15 18:42 inode-state
    -rw-r--r-- 1 root root 0 Nov 15 18:42 lease-break-time
    -rw-r--r-- 1 root root 0 Nov 15 18:42 leases-enable
    dr-xr-xr-x 2 root root 0 Nov 15 18:42 mqueue
    dr-xr-xr-x 2 root root 0 Nov 15 18:42 nfs
    -rw-r--r-- 1 root root 0 Nov 15 18:42 overflowgid
    -rw-r--r-- 1 root root 0 Nov 15 18:42 overflowuid
    dr-xr-xr-x 2 root root 0 Nov 15 18:42 quota




    many thank for your help

  2. #2
    Join Date
    Sep 2005
    Location
    France, Paris
    Posts
    34
    Hello Titou


    I'm not system engineer , I might be wrong, I only hope this help you in your investigations.

    Seems that fs.aio-max-size is used when Asynchronous I/O is set:
    What about your kernel version ?
    According quick search I make on internet it seems that Asynchronous I/O can be used on RAWIO, EXT2, EXT3, REISERFS filesystem and is not supported on NFS.
    Does your kernel support one of these FS ?
    I heard about a Async I/O library as well: libaio. Not sure it exists or not in your redhat box.

    Might be possible for you to recompile the kernel...

    Anyone more familiar at this OS level ?

    Best Regards,
    Last edited by jflebon; 11-15-05 at 19:47.
    Regards.

  3. #3
    Join Date
    Jan 2003
    Location
    Geneva, Switzerland
    Posts
    353
    I also answered in the Sybase forums... but:

    This kernel parameter doesn't exist in the 2.6.x kernel as those performance improvements have been integrated into the standard device drivers and are based on the physical capabilities of the HBA drivers (maximum number of concurrent 4K blocks that the driver can handle, IIRC).

    BTW - I found this information by a quick google search on fs.aio-max-size and 2.6 :-)

    Michael

  4. #4
    Join Date
    May 2005
    Location
    Paris
    Posts
    46
    ok, many thank Michael.


    Christophe

Posting Permissions

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