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Date: Tue, 5 May 2009 23:24:31 +0200 (CEST) From: Jesper Dangaard Brouer <hawk@...u.dk> To: David Miller <davem@...emloft.net> Cc: jeffrey.t.kirsher@...el.com, hawk@...x.dk, netdev <netdev@...r.kernel.org>, e1000-devel@...ts.sourceforge.net, jesse.brandeburg@...el.com, bruce.w.allan@...el.com, peter.p.waskiewicz.jr@...el.com, john.ronciak@...el.com Subject: Re: [PATCH] igb: Record hardware RX overruns in net_stats On Tue, 5 May 2009, David Miller wrote: > From: Jeff Kirsher <jeffrey.t.kirsher@...el.com> > Date: Tue, 5 May 2009 11:47:09 -0700 > >> NAK. RNBC is not a counter for buffer overruns, and so should not be >> counted as such. > > I'd say technically it is, it indicates that more packets arrived than > the available receive buffers could handle. I agree with DaveM. Technically it _is_ a buffer overflow, but in the host memory not the NIC. I'm sort of pushing the system into a situation where it cannot empty the receive buffers fast enough. I can fairly easily provoke this situation by adding too many iptables rules, which (intentionally) cause high CPU load and causes ksoftirqd to run (I'm Oprofiling netfilter modules). > If anything, this is the closest this device has for this kind of > situation, and it's useful for diagnosing problems. Its really useful for diagnosing problems, and I'm betting that this is a real-life situation which people is going to experience. We might as well help our self to more easily identify this issue when people report drop problems. Notice that I'm seeing: rx_no_buffer_count: 136955 rx_missed_errors: 0 Thus, the rx_missed_errors is zero, which according to the datasheet is the "real" fifo drop (the MPC register, Missed Packets Count) and PCI bandwidth problem indications. If we really should nitpick, then: adapter->net_stats.rx_missed_errors = adapter->stats.mpc Should then have been stored in the rx_fifo_errors. Notice that rx_missed_errors is presented to userspace as drops (see net/core/dev.c:2624). I think that both MPC and RNBC should be stored in rx_fifo_errors (and of cause still keeping them seperate to ethtool -S). I'll post two patches with these changes tomorrow, for you evaluation. Please reconsider you NAK. Greetings, Jesper Brouer -- ------------------------------------------------------------------- MSc. Master of Computer Science Dept. of Computer Science, University of Copenhagen Author of http://www.adsl-optimizer.dk ------------------------------------------------------------------- -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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