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Date: Fri, 28 Feb 2014 17:14:58 -0500 From: Vlad Yasevich <vyasevic@...hat.com> To: Christian Borntraeger <borntraeger@...ibm.com> CC: "David S. Miller" <davem@...emloft.net>, Jason Wang <jasowang@...hat.com>, "Michael S. Tsirkin" <mst@...hat.com>, netdev@...r.kernel.org, KVM list <kvm@...r.kernel.org>, Linux Kernel Mailing List <linux-kernel@...r.kernel.org> Subject: Re: macvtap performance regression (bisected) between 3.13 and 3.14-rc1 On 02/27/2014 03:52 PM, Christian Borntraeger wrote: > Vlad, > > commit 6acf54f1cf0a6747bac9fea26f34cfc5a9029523 > macvtap: Add support of packet capture on macvtap device. > > causes a performance regression for iperf traffic between two KVM guests > on my s390 system. Both guests are connected via two macvtaps on the same OSA > network card. > Before that patch I get ~20 Gbit/sec between two guests, afterwards I get > ~4Gbit/sec > > Latency seems to be unchanges (uperf 1byte ping pong). > > According to ifconfig in the guest, I have ~ 1500 bytes per packet with this > patch and ~ 40000 bytes without. So for some reason this patch causes the > network stack to do segmentation. (the guest kernel stays the same, only host > kernel is changed). > > Any ideas? I am looking. It shouldn't cause addition segmentations and when I ran netperf on the code I didn't see any difference in the throughput. -vlad > > > Christian > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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