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Message-ID: <1200349909.15122.31.camel@dell> Date: Mon, 14 Jan 2008 14:31:49 -0800 From: "Michael Chan" <mchan@...adcom.com> To: "Mark Seger" <Mark.Seger@...com> cc: "netdev" <netdev@...r.kernel.org> Subject: Re: Why are network counters only updated once a second? On Mon, 2008-01-14 at 15:30 -0500, Mark Seger wrote: > Eventually the frequency became better aligned at a 1 second interval > because now the number look better, but the problem I see is that when > the sampling interval is very close to the monitoring interval you still > get periodic incorrect data. Furthermore, you now need to know which > way the counters are updated before you pick a sampling interval! But > the real point is if anyone ever wants to do finer grained monitoring, > say every 1/2 or even tenth of a second, they can't because the counters > won't change between samples. Has this ever been discussed before? On most Broadcom NICs, the statistics counters are periodically DMA'ed from the chip and the default interval is roughly 1 second. On most of these chips, you can override this interval using ethtool -C eth0. As I mentioned earlier, the 5706/5708 has a bug in the statistics DMA engine that can corrupt counters from time to time. The workaround is effective, but you now lose the ability to control the DMA interval. -- 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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