2.4.21 opteron 32 Gig RAM has 10k block writes/sec on running posgresql 7.4.6 disk i/o intensive app

From: Paramveer Singh (kernel.mail_at_gmail.com)
Date: 12/23/04

  • Next message: William Lee Irwin III: "Re: 2.4.21 opteron 32 Gig RAM has 10k block writes/sec on running posgresql 7.4.6 disk i/o intensive app" 
    Date:	Thu, 23 Dec 2004 12:26:48 +0530
To: linux-kernel@vger.kernel.org

    we are using a RedHat AS3 U3 box (2.4.21-4.ELsmp) to run a very
    intensive database app which does a _huge_ number of inserts durnig
    the data generation phase. However, we are noticing a unexpected
    performance drops with user cpu utilization numbers falling to near 0.

    most of the cpu is used up in iowait.
    CPU states: cpu user nice system irq softirq iowait idle
              total 2.0% 0.0% 7.6% 0.0% 0.0% 362.4% 27.2%

    /proc/slabinfo showed huge numbers in buffer_head. The line was:
    buffer_head 4908452 4962249 200 260854 261171 1 : 16000 4000

    some lines from vmstat 1
    procs memory swap io system cpu
     r b swpd free buff cache si so bi bo in cs us sy wa id
     4 2 10104 8585908 109820 19090508 0 0 37 1160 282 1421
    8 4 67 22
     1 4 10104 8585908 109824 19090684 0 0 0 4940 1359 4762
    4 1 42 52
     0 3 10104 8585908 109824 19091084 0 0 0 5296 1442 17178
    13 4 40 43
     8 1 10104 8585908 109824 19092068 0 0 0 2856 1437 34481
    33 6 30 32
     1 3 10104 8585908 109832 19093620 0 0 0 9012 1538 28554
    35 7 34 25
     0 3 10104 8585908 109832 19094004 0 0 0 6120 1552 3059
    6 2 47 45
     0 3 10104 8585908 109836 19094012 0 0 0 6188 1502 332
    0 0 70 30
     0 3 10104 8585908 109836 19094020 0 0 0 6436 1548 865
    0 1 67 32
     2 3 10104 8585908 109836 19094332 0 0 0 5980 1404 9322
    10 3 52 36
     0 3 10104 8585908 109840 19094332 0 0 0 5252 1492 190
    0 0 74 25

    Interestingly, the swap is not being used at all
    free output:
    Swap: 2040212 10104 2030108

    the box is
    Quad AMD Opteron 1.8Ghz
    Tyan Mother board S4882UG2NR
    with Rack Chassis, 12 X 1 Hot swap bays, power supply + RPS Support
    32Gb DDr sdram @ 266
    8 X 80Gb SATA Hot Swap Hard Drive, 7200 RPM
    Adaptec SATA RAID controller

    I tried to google but found some kswapd related bugs in AS3 which were
    fixed in U3. We upgraded even though this does not seem to be a kswapd
    error. I am gussing I have used some inappropriate numbers while
    setting up the box.

    Would someone be kind to point me in a direction where I can find more
    information?

    thanks a lot!
    ps
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  • Next message: William Lee Irwin III: "Re: 2.4.21 opteron 32 Gig RAM has 10k block writes/sec on running posgresql 7.4.6 disk i/o intensive app"

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