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    SubjectPerformance issue in 2.5.32+
    I've noticed a significant performance hit on my system since 2.5.32.  
    lmbench shows major changes in context switching latencies for 2.5.32 and
    2.5.33 (see below, and profiling results for lat_ctx after that). This is
    on a dual celeron system with a Gigabyte GA6BXD motherboard. I can
    provide more hardware and configuration details if required.


    L M B E N C H 2 . 0 S U M M A R Y
    ------------------------------------


    Basic system parameters
    ----------------------------------------------------
    Host OS Description Mhz

    --------- ------------- ----------------------- ----
    test1 Linux 2.4.19 i686-pc-linux-gnu 548
    test1 Linux 2.5.31 i686-pc-linux-gnu 547
    test1 Linux 2.5.32 i686-pc-linux-gnu 547
    test1 Linux 2.5.33 i686-pc-linux-gnu 547

    Processor, Processes - times in microseconds - smaller is better
    ----------------------------------------------------------------
    Host OS Mhz null null open selct sig sig fork exec sh
    call I/O stat clos TCP inst hndl proc proc proc
    --------- ------------- ---- ---- ---- ---- ---- ----- ---- ---- ---- ---- ----
    test1 Linux 2.4.19 548 0.64 1.09 6.04 8.10 49.9 1.52 4.81 498. 1399 6546
    test1 Linux 2.5.31 547 0.61 1.15 6.77 9.91 44.2 1.48 5.12 576. 1698 7381
    test1 Linux 2.5.32 547 0.64 1.18 6.24 9.64 1.52 5.08 703. 1884 8014
    test1 Linux 2.5.33 547 0.64 1.15 6.29 8.18 1.52 5.08 733. 1884 7965

    Context switching - times in microseconds - smaller is better
    -------------------------------------------------------------
    Host OS 2p/0K 2p/16K 2p/64K 8p/16K 8p/64K 16p/16K 16p/64K
    ctxsw ctxsw ctxsw ctxsw ctxsw ctxsw ctxsw
    --------- ------------- ----- ------ ------ ------ ------ ------- -------
    test1 Linux 2.4.19 2.890 10.7 94.5 34.1 130.8 35.9 135.0
    test1 Linux 2.5.31 7.160 12.8 64.4 21.8 131.7 38.4 133.6
    test1 Linux 2.5.32 1.460 1085.4 95.1 333.1 1078.8 200.6 634.3
    test1 Linux 2.5.33 2.080 9.4200 93.8 37.4 1096.0 212.3 1079.8

    *Local* Communication latencies in microseconds - smaller is better
    -------------------------------------------------------------------
    Host OS 2p/0K Pipe AF UDP RPC/ TCP RPC/ TCP
    ctxsw UNIX UDP TCP conn
    --------- ------------- ----- ----- ---- ----- ----- ----- ----- ----
    test1 Linux 2.4.19 2.890 13.0 39.2 60.7 120.
    test1 Linux 2.5.31 7.160 9.213 17.5 62.0 121.
    test1 Linux 2.5.32 1.460 10.5 18.8 48.7 249.
    test1 Linux 2.5.33 2.080 10.5 17.9 8018. 192.

    File & VM system latencies in microseconds - smaller is better
    --------------------------------------------------------------
    Host OS 0K File 10K File Mmap Prot Page
    Create Delete Create Delete Latency Fault Fault
    --------- ------------- ------ ------ ------ ------ ------- ----- -----
    test1 Linux 2.4.19 117.2 36.4 316.4 73.6 1811.0 1.234 4.00000
    test1 Linux 2.5.31 123.6 40.5 341.5 83.5 3120.0 1.316 5.00000
    test1 Linux 2.5.32 125.4 41.4 25.6K 5988.0 3224.0 1.223 5.00000
    test1 Linux 2.5.33 121.5 38.8 198.5 81.8 3078.0 1.327 5.00000

    *Local* Communication bandwidths in MB/s - bigger is better
    -----------------------------------------------------------
    Host OS Pipe AF TCP File Mmap Bcopy Bcopy Mem Mem
    UNIX reread reread (libc) (hand) read write
    --------- ------------- ---- ---- ---- ------ ------ ------ ------ ---- -----
    test1 Linux 2.4.19 164. 145. 78.8 216.1 443.3 155.3 154.5 443. 185.3
    test1 Linux 2.5.31 215. 123. 84.9 235.9 440.5 158.8 157.9 440. 199.5
    test1 Linux 2.5.32 203. 103. 6.75 199.5 388.8 143.7 142.0 387. 182.2
    test1 Linux 2.5.33 130. 2.42 9.07 162.7 388.7 144.8 143.1 389. 182.8

    Memory latencies in nanoseconds - smaller is better
    (WARNING - may not be correct, check graphs)
    ---------------------------------------------------
    Host OS Mhz L1 $ L2 $ Main mem Guesses
    --------- ------------- ---- ----- ------ -------- -------
    test1 Linux 2.4.19 548 5.470 100.8 133.1
    test1 Linux 2.5.31 547 5.478 87.0 133.5
    test1 Linux 2.5.32 547 5.483 102.8 146.8
    test1 Linux 2.5.33 547 5.483 110.8 146.5


    * lat_ctx profiling data for 2.5.31:

    "size=64k ovr=33.90
    16 137.67
    868 default_idle 13.5625
    24 system_call 0.5455
    14 __wake_up 0.2917
    17 do_gettimeofday 0.1181
    4 sys_gettimeofday 0.0250
    1 pgd_alloc 0.0156
    2 pte_alloc_one 0.0139
    938 total 0.0077
    6 schedule 0.0067
    1 do_page_fault 0.0009
    1 copy_process 0.0005

    * lat_ctx profiling data for 2.5.32:

    "size=64k ovr=33.85
    16 629.19
    1329 default_idle 20.7656
    22 system_call 0.5000
    23 __wake_up 0.4792
    3 syscall_call 0.2727
    1 syscall_exit 0.0909
    13 do_gettimeofday 0.0903
    8 sys_gettimeofday 0.0500
    1 ret_from_intr 0.0417
    33 schedule 0.0368
    2 remove_wait_queue 0.0312
    1 schedule_tail 0.0208
    2 pte_alloc_one 0.0139
    1445 total 0.0117
    1 cpu_idle 0.0089
    1 session_of_pgrp 0.0078
    1 do_softirq 0.0052
    1 sys_rt_sigaction 0.0042
    1 do_sigaction 0.0028
    1 copy_files 0.0014
    1 do_exit 0.0014



    - James
    --
    James Morris
    <jmorris@intercode.com.au>


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