Messages in this thread | | | Date | Tue, 22 Jan 2008 06:46:45 +0100 | From | Eric Dumazet <> | Subject | Re: questions on NAPI processing latency and dropped network packets |
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Chris Friesen a écrit : > Eric Dumazet wrote: >> Chris Friesen a écrit : >> >>> I've done some further digging, and it appears that one of the >>> problems we may be facing is very high instantaneous traffic rates. >>> >>> Instrumentation showed up to 222K packets/sec for short periods (at >>> least 1.1 ms, possibly longer), although the long-term average is >>> down around 14-16K packets/sec. >> >> >> Instrumentation done where exactly ? > > I added some code to e1000_clean_rx_irq() to track rx_fifo drops, total > packets received, and an accurate timestamp. > > If rx_fifo errors changed, it would dump the information. > >>> Is there anything else we can do to minimize the latency of network >>> packet processing and avoid having to crank the rx ring size up so high? > >> You have some tasks that disable softirqs too long. Sometimes, bumping >> RX ring size is OK (but you will still have delays), sometimes it is >> not an option, since 4096 is the limit on current hardware. > > I added some instrumentation to take timestamps in __do_softirq() as > well. Based on these timestamps, I can see the following code sequence: > > 2374604616 usec, start processing softirqs in __do_softirq() > 2374610337 usec, log values in e1000_clean_rx_irq() > 2374611411 usec, log values in e1000_clean_rx_irq() > > In between the successive calls to e1000_clean_rx_irq() the rx_fifo > counts went up. > > Does anyone have any patchsets to track down what softirqs are taking a > long time, and/or who's disabling softirqs? >
Not for linux-2.6.10 unfortunatly.
Check net/ipv4/route.c, where many improvements can be done, especially if you have a large rt cache
grep . /proc/sys/net/ipv4/route/*
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