lkml.org 
[lkml]   [2002]   [Nov]   [15]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    From
    Subject2.5.47-mm3 IO rate question
    Date
    Hi,

    I am using 2.5.47-mm3 and qlogic driver qla2x00src-v6.03.00b8.
    I have 2 qlogic controllers connected to 2 trays (10 disks/tray).

    I do 256K IO on raw devices using "dd".

    dd of=/dev/null bs=256k count=2000 if=/dev/raw/raw1 &
    dd of=/dev/null bs=256k count=2000 if=/dev/raw/raw2 &
    dd of=/dev/null bs=256k count=2000 if=/dev/raw/raw3 &
    ...
    dd of=/dev/null bs=256k count=2000 if=/dev/raw/raw20 &

    IO throughput changes just by adjusting SG_SEGMENTS (from 32 to 64).
    I was wondering why such a significant difference. (20MB/sec).

    I used to get 194-198MB/sec with 2.5.37 (with DIO code sending
    (fixed) 64K requests - qlogic max_sector=512, SG_SEGMETS=32).

    Any thoughts ?

    Thanks,
    Badari

    max_sectors = 512
    SG_SEGMENTS = 64
    [root]# vmstat 5
    procs memory swap io system cpu
    r b w swpd free buff cache si so bi bo in cs us sy id
    0 20 0 0 3642680 8832 42836 0 0 194765 15 1762 2183 0 100 0
    0 20 0 0 3642680 8836 42836 0 0 194611 3 1761 2122 0 100 0
    0 20 0 0 3642680 8840 42836 0 0 194509 3 1774 2150 10 81 8
    0 20 0 0 3642680 8844 42836 0 0 194816 3 1762 2132 2 98 0
    0 20 0 0 3642680 8848 42836 0 0 194765 3 1764 2177 2 98 0


    max_sectors = 512
    SG_SEGMENTS = 32
    [root]# vmstat 5
    procs memory swap io system cpu
    r b w swpd free buff cache si so bi bo in cs us sy id
    0 20 0 0 3652472 7752 34464 0 0 170755 15 2354 3477 2 98 0
    0 20 0 0 3652472 7756 34464 0 0 172771 3 2363 3512 2 98 0
    0 20 0 0 3652472 7760 34464 0 0 174031 3 2372 3576 0 100 0
    0 20 0 0 3652408 7764 34464 0 0 173074 7 2384 3538 10 87 3
    0 20 0 0 3652408 7768 34464 0 0 172670 3 2364 3502 2 98 0

    -
    To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
    the body of a message to majordomo@vger.kernel.org
    More majordomo info at http://vger.kernel.org/majordomo-info.html
    Please read the FAQ at http://www.tux.org/lkml/

    \
     
     \ /
      Last update: 2005-03-22 13:31    [W:3.118 / U:0.008 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site