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    SubjectRe: Linux 2.6.9 latencies: scheduler bug?
    On Mon, Oct 25, 2004 at 12:26:18AM +0300, Sami Farin wrote:
    ...
    > while that's running, "rtc_latencytest 1024" has max latencies of 253ms.
    > $BLOCKLIST has around two thousand lines.
    > http://safari.iki.fi/ip_tables_original_maxlat_253ms.png
    > from pressing sysrq+p while it was running, I guesstimated one evil spot
    > and added cond_resched() in there :)
    > http://safari.iki.fi/ip_tables_cond_resched.png
    > at 5s I started the script.

    forget this stupid ip_tables.c patch, latencies have nothing to do with
    netfilter code, but bad interaction between xmms, rtc_latencytest
    and iptables. I now get at max 3.1s (yup, 3100000us) latencies.
    http://safari.iki.fi/2.6.9-xmms-fun-1.png
    if you want to reproduce this:
    1) run "rtc_latencytest 1024" (can't reproduce with "rtc_latencytest 512")
    2) press play in xmms
    3) start iptables-script

    xmms has to be prepared first.
    a) put it in repeat mode
    b) start playing >= 2 files (like that short testcase.mp3 from lame)
    c) remove the files while xmms is playing
    d) wait till xmms has played all of the selected files
    e) press stop [now then you press play in 2), xmms does silly infinite
    loop without delays while trying to open the songs]

    please give me patches to try, 3.1s is really evil 8-)

    the iptables-loop is
    iptables -N FSCKMEHARDER
    cat /service/rbldnsd/dsbl.org/rbldns-list.dsbl.org | while read ip;
    do iptables -A FSCKMEHARDER -p tcp -s $ip -j DROP;
    done
    alternatively, you can generate random IPs, doesn't probably
    make any difference.

    I have xorg-x11-6.8.1-12 and Matrox G200, if that matters.

    xmms is doing these system calls...
    $ awk '{print $3}' xmms-strace.txt |sort|uniq -c|sort -n
    1 close(-1
    1 setup(
    7 nanosleep({0,
    18 gettimeofday({1098704731,
    35 select(5,
    43 gettimeofday({1098704728,
    47 gettimeofday({1098704729,
    47 gettimeofday({1098704730,
    83 <...
    154 close(-1)
    155 ioctl(3,
    155 poll([{fd=3,
    155 readv(3,
    312 open("/var/temp/testcase.mp3",
    385 open("/var/temp/testcase.mp3.wav",
    465 write(3,
    466 select(4,
    930 read(3,

    /proc/vmstat before and after running rtc_latencytest.

    before
    nr_dirty 0
    nr_writeback 0
    nr_unstable 0
    nr_page_table_pages 919
    nr_mapped 46485
    nr_slab 4320
    pgpgin 1235396
    pgpgout 532242
    pswpin 9795
    pswpout 32253
    pgalloc_high 0
    pgalloc_normal 30934240
    pgalloc_dma 18350
    pgfree 30955504
    pgactivate 187837
    pgdeactivate 157183
    pgfault 19090447
    pgmajfault 7616
    pgrefill_high 0
    pgrefill_normal 3472213
    pgrefill_dma 76329
    pgsteal_high 0
    pgsteal_normal 341889
    pgsteal_dma 4460
    pgscan_kswapd_high 0
    pgscan_kswapd_normal 423918
    pgscan_kswapd_dma 5894
    pgscan_direct_high 0
    pgscan_direct_normal 14982
    pgscan_direct_dma 0
    pginodesteal 0
    slabs_scanned 397568
    kswapd_steal 343850
    kswapd_inodesteal 35158
    pageoutrun 11989
    allocstall 49
    pgrotated 29549

    after
    nr_dirty 0
    nr_writeback 0
    nr_unstable 0
    nr_page_table_pages 919
    nr_mapped 46496
    nr_slab 4334
    pgpgin 1235396
    pgpgout 532286
    pswpin 9795
    pswpout 32253
    pgalloc_high 0
    pgalloc_normal 31500853
    pgalloc_dma 18771
    pgfree 31522633
    pgactivate 188101
    pgdeactivate 157185
    pgfault 19627511
    pgmajfault 7616
    pgrefill_high 0
    pgrefill_normal 3474226
    pgrefill_dma 76395
    pgsteal_high 0
    pgsteal_normal 342045
    pgsteal_dma 4460
    pgscan_kswapd_high 0
    pgscan_kswapd_normal 424347
    pgscan_kswapd_dma 5894
    pgscan_direct_high 0
    pgscan_direct_normal 14982
    pgscan_direct_dma 0
    pginodesteal 0
    slabs_scanned 397696
    kswapd_steal 344006
    kswapd_inodesteal 35158
    pageoutrun 11994
    allocstall 49
    pgrotated 29549

    vmstat 1 wasn't very special.
    procs -----------memory---------- ---swap-- -----io---- --system-- ----cpu----
    r b swpd free buff cache si so bi bo in cs us sy id wa
    4 1 119480 10384 11444 45444 0 0 0 4 2100 1837 49 51 0 0
    3 1 119480 10264 11444 45444 0 0 0 0 2095 2238 41 59 0 0
    3 1 119480 9424 11444 45444 0 0 0 0 2088 1923 37 63 0 0
    3 1 119480 10804 11444 45444 0 0 0 0 2087 998 40 60 0 0

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