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    SubjectRe: Pin-pointing the root of unusual application latencies
    John Sigler wrote:

    > ( check_dektec_in-1095 |#0): new 271 us user-latency.
    > ( check_dektec_in-1095 |#0): new 275 us user-latency.
    > ( check_dektec_in-1095 |#0): new 290 us user-latency.
    > ( check_dektec_in-1095 |#0): new 297 us user-latency.
    > ( check_dektec_in-1095 |#0): new 345 us user-latency.
    > ( check_dektec_in-1095 |#0): new 358 us user-latency.
    > ( check_dektec_in-1095 |#0): new 384 us user-latency.
    > ( check_dektec_in-1095 |#0): new 392 us user-latency.
    > ( check_dektec_in-1095 |#0): new 395 us user-latency.
    > ( check_dektec_in-1095 |#0): new 396 us user-latency.
    > ( check_dektec_in-1095 |#0): new 1031 us user-latency.
    > ( check_dektec_in-1095 |#0): new 1100 us user-latency.
    > ( check_dektec_in-1095 |#0): new 1105 us user-latency.
    > ( check_dektec_in-1095 |#0): new 1106 us user-latency.
    >
    > Here's the function trace for the 1106-µs latency:
    >
    > http://linux.kernel.free.fr/latency/1106-us-trace.txt

    The function trace for 400-µs latencies is different:

    ( check_dektec_in-1145 |#0): new 275 us user-latency.
    ( check_dektec_in-1145 |#0): new 276 us user-latency.
    ( check_dektec_in-1145 |#0): new 288 us user-latency.
    ( check_dektec_in-1145 |#0): new 289 us user-latency.
    ( check_dektec_in-1145 |#0): new 289 us user-latency.
    ( check_dektec_in-1145 |#0): new 290 us user-latency.
    ( check_dektec_in-1145 |#0): new 297 us user-latency.
    ( check_dektec_in-1145 |#0): new 345 us user-latency.
    ( check_dektec_in-1145 |#0): new 354 us user-latency.
    ( check_dektec_in-1145 |#0): new 377 us user-latency.
    ( check_dektec_in-1145 |#0): new 393 us user-latency.

    http://linux.kernel.free.fr/latency/393-us-trace.txt

    There are ~200 calls to ioread32 from mdio_read from speedo_timer.

    http://lxr.linux.no/source/drivers/net/eepro100.c#L1159
    http://lxr.linux.no/source/drivers/net/eepro100.c#L928

    In this case, and as far as I understand, the culprit is the eepro100
    driver talking to one of the NICs (which one?). Is that correct?

    What is the consequence of IRQ10 being shared by eth2 and
    by my I/O board?

    How can I force Linux to assign different IRQs to every peripheral
    if I have free IRQs lines?

    Regards.
    -
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