[lkml]   [2008]   [Jan]   [14]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
    SubjectRe: questions on NAPI processing latency and dropped network packets
    Chris Friesen a écrit :
    > Ray Lee wrote:
    >> On Jan 10, 2008 9:24 AM, Chris Friesen <> wrote:
    >>> After a recent userspace app change, we've started seeing packets being
    >>> dropped by the ethernet hardware (e1000, NAPI is enabled). The
    >>> error/dropped/fifo counts are going up in ethtool:
    >> Can you reproduce it with a simple userspace cpu hog? (Two, really,
    >> one per cpu.)
    >> Can you reproduce it with the newer e1000?
    > Hmm...good questions and I haven't checked either. The first one is
    > relatively straightforward. The second is a bit trickier...last time
    > I tried the latest e1000 driver the card wouldn't boot (we use netboot).
    >> Can you reproduce it with git head?
    > Unfortunately, I don't think I'll be able to try this. We require
    > kernel mods for our userspace to run, and I doubt I'd be able to get
    > the time to port all the changes forward to git head.
    >> If the answer to the first one is yes, the last no, then bisect until
    >> you get a kernel that doesn't show the problem. Backport the fix,
    >> unless the fix happens to be CFS. However, I suspect that your
    >> userpace app is just starving the system from time to time.
    > It's conceivable that userspace is starving the kernel, but we have do
    > about 45% idle on one cpu, and 7-10% idle on the other.
    > We also have an odd situation where on an initial test run after
    > bootup we have 18-24% idle on cpu1, but resetting the test tool drops
    > that to the 7-10% I mentioned above.
    > Based on profiling and instrumentation it seems like the cost of
    > sctp_endpoint_lookup_assoc() more than triples, which means that the
    > amount of time that bottom halves are disabled in that function also
    > triples.
    Any idea of the size of sctp hash size you have ?
    (your dmesg probably includes a message starting with SCTP: Hash tables

    How many concurrent sctp sockets are handled ?

    Maybe sctp_assoc_hashfn() is too weak for your use, and some chains are
    *really* long.

    To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
    the body of a message to
    More majordomo info at
    Please read the FAQ at

     \ /
      Last update: 2008-01-14 17:59    [W:0.023 / U:20.832 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site