[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-devel] Interrupt Coalescence
I've found that Interrupt Coalescence (IC) has a detrimental effect on some benchmarks with the e1000 driver. So I tried disabling it with the argument "InterruptThrottleRate=0,0". This had the wanted effect in native linux, ie. full speed, 116 MB/s. However, in Xen0, disabling IC has the effect of severely reducing bandwidth down to around 1 MB/s. Turning of IC has the effect that an interrupt is generated from the NIC for each received or sent MTU (1500 bytes). On a gigabit network this means that an interrupt may be generated, according to [http://www.pam2004.org/papers/265.pdf], every 12 us. I looked at #interrupts generated with and without IC, and they are ~ 1100 and ~ 400 respectively when sending a 2 MB message with ttcp. So I'm trying to explain what's happening. Is Xen slower in handling the interrupts than native? The CPU is an Intel P4 @ 3400 MHz. Does it need more than 12 us to do a context switch when using Xen? Håvard ------------------------------------------------------- This SF.Net email is sponsored by: Sybase ASE Linux Express Edition - download now for FREE LinuxWorld Reader's Choice Award Winner for best database on Linux. http://ads.osdn.com/?ad_idU88&alloc_id065&op=click _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.sourceforge.net/lists/listinfo/xen-devel
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