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Date: Thu, 19 Dec 2013 17:30:54 -0800 From: Eric Dumazet <eric.dumazet@...il.com> To: Florian Fainelli <f.fainelli@...il.com> Cc: netdev <netdev@...r.kernel.org>, therbert@...gle.com Subject: Re: Excessive IPI interrupts with single RX queue devices and rps_cpus mask set On Thu, 2013-12-19 at 17:12 -0800, Florian Fainelli wrote: > Hello, > > After configuring the rps_cpus mask to enable all CPUs for a single RX > queue network device, I noticed that I was getting one interrupt per > packet received, with the interrupt count being splitted between NAPI > interrupts and IPI SMP interrupts. > > This behavior was observed on 3.8.13 as well as 3.3. The host was > receiving a Gigabit UDP stream and the receiver was not consuming the > SKBs. Whenever there was a listener consuming the SKBs received, the > number of IPI/sec quickly jumped to about 4 times the number without a > rps_cpus mask. > > Shall we prevent the rps_cpu mask to be set at all for single RX queue > devices since this seems to causes excessive IPI interrupts? Not sure what you mean. This is the thing that highly depends on workload. (Most workloads perform better without RPS/RFS) This is why it is disabled by default. -- 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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