On Tue, Sep 27, 2011 at 08:10:21PM +0200, Reeted wrote: -netdev is just an alternative way of setting up networking that avoids QEMU's nasty VLAN concept. Using -netdev allows QEMU to use more efficient codepaths for networking, which should improve the network performance. This shows KVM is being requested, but we should validate that KVM is definitely being activated when under libvirt. You can test this by doing: virsh qemu-monitor-command vmname1 'info kvm' Fine, has no effect on performance. You could have equivalently used -netdev tap,ifname=tap0,script=no,downscript=no,id=hostnet0,vhost=on -device virtio-net-pci,netdev=hostnet0,id=net0,mac=52:54:00:05:36:60,bus=pci.0,addr=0x3 That said, I don't expect this has anything todo with the performance since booting a guest rarely involves much network I/O unless you're doing something odd like NFS-root / iSCSI-root. Yeah, I have never seen VNC be responsible for the kind of slowdown you describe. Probably, but again I dont think it is likely to be relevant here. There are a couple of things that would be different between running the VM directly, vs via libvirt. - Security drivers - SELinux/AppArmour - CGroups If it is was AppArmour causing this slowdown I don't think you would have been the first person to complain, so lets ignore that. Which leaves cgroups as a likely culprit. Do a grep cgroup /proc/mounts if any of them are mounted, then for each cgroups mount in turn, - Umount the cgroup - Restart libvirtd - Test your guest boot performance Regards, Daniel -- |: http://berrange.com -o- http://www.flickr.com/photos/dberrange/ :| |: http://libvirt.org -o- http://virt-manager.org :| |: http://autobuild.org -o- http://search.cpan.org/~danberr/ :| |: http://entangle-photo.org -o- http://live.gnome.org/gtk-vnc :|

On Wed, Sep 28, 2011 at 11:19:43AM +0200, Reeted wrote: Ok, that is truely bizarre and I don't really have any explanation for why that is. I guess you could try 'vhost=off' too and see if that makes the difference. Hmm, none of that looks particularly suspect. So I don't really have much idea what else to try apart from the 'vhost=off' possibilty. Daniel -- |: http://berrange.com -o- http://www.flickr.com/photos/dberrange/ :| |: http://libvirt.org -o- http://virt-manager.org :| |: http://autobuild.org -o- http://search.cpan.org/~danberr/ :| |: http://entangle-photo.org -o- http://live.gnome.org/gtk-vnc :|

On Wed, Sep 28, 2011 at 11:49:01AM +0200, Reeted wrote: I've no idea. I was always under the impression that 'vhost=on' was the 'make it go much faster' switch. So something is going wrong here that I cna't explain. Perhaps one of the network people on this list can explain... To turn vhost off in the libvirt XML, you should be able to use <driver name='qemu'/> for the interface in question,eg <interface type='user'> <mac address='52:54:00:e5:48:58'/> <model type='virtio'/> <driver name='qemu'/> </interface> Regards, Daniel -- |: http://berrange.com -o- http://www.flickr.com/photos/dberrange/ :| |: http://libvirt.org -o- http://virt-manager.org :| |: http://autobuild.org -o- http://search.cpan.org/~danberr/ :| |: http://entangle-photo.org -o- http://live.gnome.org/gtk-vnc :|

On Wed, Sep 28, 2011 at 12:19:09PM +0200, Reeted wrote: Be sure to CC the qemu-devel mailing list too next time, since that has a wider audience who might be able to help Daniel -- |: http://berrange.com -o- http://www.flickr.com/photos/dberrange/ :| |: http://libvirt.org -o- http://virt-manager.org :| |: http://autobuild.org -o- http://search.cpan.org/~danberr/ :| |: http://entangle-photo.org -o- http://live.gnome.org/gtk-vnc :|

On 09/28/11 14:56, Richard W.M. Jones wrote: Of the two qemu-kvm processes (threads?) which I see consuming CPU for that VM, one is at about 20%, the other at about 10%. I think it's doing something but maybe not much, or maybe it's really I/O bound and the I/O is slow (as I originarily thought). I will perform some disk benchmarks and follow up, but I can't do that right now... Thank you

* Reeted (reeted(a)shiftmail.org) wrote: OK, I re-read it (pretty sure FC6 had the old dhclient, which is why I wondered). That is odd. No ideas are springing to mind. thanks, -chris

On 10/05/11 01:12, Reeted wrote: Just a small update, Firstly: I cannot reproduce any slowness after boot by doing: # time /etc/init.d/chrony restart Restarting time daemon: Starting /usr/sbin/chronyd... chronyd is running and online. real 0m3.022s user 0m0.000s sys 0m0.000s since this is a network service I expected it to show the problem, but it doesn't. It takes exactly same time with and without vhost_net. Secondly, vhost_net appears to work correctly, because I have performed a NPtcp performance test between two guests in the same host, and these are the results: vhost_net deactivated for both hosts: NPtcp -h 192.168.7.81 Send and receive buffers are 16384 and 87380 bytes (A bug in Linux doubles the requested buffer sizes) Now starting the main loop 0: 1 bytes 917 times --> 0.08 Mbps in 92.07 usec 1: 2 bytes 1086 times --> 0.18 Mbps in 86.04 usec 2: 3 bytes 1162 times --> 0.27 Mbps in 85.08 usec 3: 4 bytes 783 times --> 0.36 Mbps in 85.34 usec 4: 6 bytes 878 times --> 0.54 Mbps in 85.42 usec 5: 8 bytes 585 times --> 0.72 Mbps in 85.31 usec 6: 12 bytes 732 times --> 1.07 Mbps in 85.52 usec 7: 13 bytes 487 times --> 1.16 Mbps in 85.52 usec 8: 16 bytes 539 times --> 1.43 Mbps in 85.26 usec 9: 19 bytes 659 times --> 1.70 Mbps in 85.43 usec 10: 21 bytes 739 times --> 1.77 Mbps in 90.71 usec 11: 24 bytes 734 times --> 2.13 Mbps in 86.13 usec 12: 27 bytes 822 times --> 2.22 Mbps in 92.80 usec 13: 29 bytes 478 times --> 2.35 Mbps in 94.02 usec 14: 32 bytes 513 times --> 2.60 Mbps in 93.75 usec 15: 35 bytes 566 times --> 3.15 Mbps in 84.77 usec 16: 45 bytes 674 times --> 4.01 Mbps in 85.56 usec 17: 48 bytes 779 times --> 4.32 Mbps in 84.70 usec 18: 51 bytes 811 times --> 4.61 Mbps in 84.32 usec 19: 61 bytes 465 times --> 5.08 Mbps in 91.57 usec 20: 64 bytes 537 times --> 5.22 Mbps in 93.46 usec 21: 67 bytes 551 times --> 5.73 Mbps in 89.20 usec 22: 93 bytes 602 times --> 8.28 Mbps in 85.73 usec 23: 96 bytes 777 times --> 8.45 Mbps in 86.70 usec 24: 99 bytes 780 times --> 8.71 Mbps in 86.72 usec 25: 125 bytes 419 times --> 11.06 Mbps in 86.25 usec 26: 128 bytes 575 times --> 11.38 Mbps in 85.80 usec 27: 131 bytes 591 times --> 11.60 Mbps in 86.17 usec 28: 189 bytes 602 times --> 16.55 Mbps in 87.14 usec 29: 192 bytes 765 times --> 16.80 Mbps in 87.19 usec 30: 195 bytes 770 times --> 17.11 Mbps in 86.94 usec 31: 253 bytes 401 times --> 22.04 Mbps in 87.59 usec 32: 256 bytes 568 times --> 22.64 Mbps in 86.25 usec 33: 259 bytes 584 times --> 22.68 Mbps in 87.12 usec 34: 381 bytes 585 times --> 33.19 Mbps in 87.58 usec 35: 384 bytes 761 times --> 33.54 Mbps in 87.36 usec 36: 387 bytes 766 times --> 33.91 Mbps in 87.08 usec 37: 509 bytes 391 times --> 44.23 Mbps in 87.80 usec 38: 512 bytes 568 times --> 44.70 Mbps in 87.39 usec 39: 515 bytes 574 times --> 45.21 Mbps in 86.90 usec 40: 765 bytes 580 times --> 66.05 Mbps in 88.36 usec 41: 768 bytes 754 times --> 66.73 Mbps in 87.81 usec 42: 771 bytes 760 times --> 67.02 Mbps in 87.77 usec 43: 1021 bytes 384 times --> 88.04 Mbps in 88.48 usec 44: 1024 bytes 564 times --> 88.30 Mbps in 88.48 usec 45: 1027 bytes 566 times --> 88.63 Mbps in 88.40 usec 46: 1533 bytes 568 times --> 71.75 Mbps in 163.00 usec 47: 1536 bytes 408 times --> 72.11 Mbps in 162.51 usec 48: 1539 bytes 410 times --> 71.71 Mbps in 163.75 usec 49: 2045 bytes 204 times --> 95.40 Mbps in 163.55 usec 50: 2048 bytes 305 times --> 95.26 Mbps in 164.02 usec 51: 2051 bytes 305 times --> 95.33 Mbps in 164.14 usec 52: 3069 bytes 305 times --> 141.16 Mbps in 165.87 usec 53: 3072 bytes 401 times --> 142.19 Mbps in 164.83 usec 54: 3075 bytes 404 times --> 150.68 Mbps in 155.70 usec 55: 4093 bytes 214 times --> 192.36 Mbps in 162.33 usec 56: 4096 bytes 307 times --> 193.21 Mbps in 161.74 usec 57: 4099 bytes 309 times --> 213.24 Mbps in 146.66 usec 58: 6141 bytes 341 times --> 330.80 Mbps in 141.63 usec 59: 6144 bytes 470 times --> 328.09 Mbps in 142.87 usec 60: 6147 bytes 466 times --> 330.53 Mbps in 141.89 usec 61: 8189 bytes 235 times --> 437.29 Mbps in 142.87 usec 62: 8192 bytes 349 times --> 436.23 Mbps in 143.27 usec 63: 8195 bytes 349 times --> 436.99 Mbps in 143.08 usec 64: 12285 bytes 349 times --> 625.88 Mbps in 149.75 usec 65: 12288 bytes 445 times --> 626.27 Mbps in 149.70 usec 66: 12291 bytes 445 times --> 626.15 Mbps in 149.76 usec 67: 16381 bytes 222 times --> 793.58 Mbps in 157.48 usec 68: 16384 bytes 317 times --> 806.90 Mbps in 154.91 usec 69: 16387 bytes 322 times --> 796.81 Mbps in 156.90 usec 70: 24573 bytes 318 times --> 1127.58 Mbps in 166.26 usec 71: 24576 bytes 400 times --> 1125.20 Mbps in 166.64 usec 72: 24579 bytes 400 times --> 1124.84 Mbps in 166.71 usec 73: 32765 bytes 200 times --> 1383.86 Mbps in 180.64 usec 74: 32768 bytes 276 times --> 1376.05 Mbps in 181.68 usec 75: 32771 bytes 275 times --> 1377.47 Mbps in 181.51 usec 76: 49149 bytes 275 times --> 1824.90 Mbps in 205.48 usec 77: 49152 bytes 324 times --> 1813.95 Mbps in 206.73 usec 78: 49155 bytes 322 times --> 1765.68 Mbps in 212.40 usec 79: 65533 bytes 156 times --> 2193.44 Mbps in 227.94 usec 80: 65536 bytes 219 times --> 2186.79 Mbps in 228.65 usec 81: 65539 bytes 218 times --> 2186.98 Mbps in 228.64 usec 82: 98301 bytes 218 times --> 2831.01 Mbps in 264.92 usec 83: 98304 bytes 251 times --> 2804.76 Mbps in 267.40 usec 84: 98307 bytes 249 times --> 2824.62 Mbps in 265.53 usec 85: 131069 bytes 125 times --> 3106.48 Mbps in 321.90 usec 86: 131072 bytes 155 times --> 3033.71 Mbps in 329.63 usec 87: 131075 bytes 151 times --> 3044.89 Mbps in 328.43 usec 88: 196605 bytes 152 times --> 4196.94 Mbps in 357.40 usec 89: 196608 bytes 186 times --> 4358.25 Mbps in 344.17 usec 90: 196611 bytes 193 times --> 4362.34 Mbps in 343.86 usec 91: 262141 bytes 96 times --> 4654.49 Mbps in 429.69 usec 92: 262144 bytes 116 times --> 4727.16 Mbps in 423.09 usec 93: 262147 bytes 118 times --> 4697.22 Mbps in 425.79 usec 94: 393213 bytes 117 times --> 5452.51 Mbps in 550.20 usec 95: 393216 bytes 121 times --> 5360.27 Mbps in 559.67 usec 96: 393219 bytes 119 times --> 5358.03 Mbps in 559.91 usec 97: 524285 bytes 59 times --> 5053.83 Mbps in 791.47 usec 98: 524288 bytes 63 times --> 5033.86 Mbps in 794.62 usec 99: 524291 bytes 62 times --> 5691.44 Mbps in 702.81 usec 100: 786429 bytes 71 times --> 5750.68 Mbps in 1043.35 usec 101: 786432 bytes 63 times --> 5809.21 Mbps in 1032.84 usec 102: 786435 bytes 64 times --> 5864.45 Mbps in 1023.12 usec 103: 1048573 bytes 32 times --> 5755.24 Mbps in 1390.03 usec 104: 1048576 bytes 35 times --> 6001.51 Mbps in 1333.00 usec 105: 1048579 bytes 37 times --> 6099.40 Mbps in 1311.61 usec 106: 1572861 bytes 38 times --> 6061.69 Mbps in 1979.64 usec 107: 1572864 bytes 33 times --> 6144.15 Mbps in 1953.08 usec 108: 1572867 bytes 34 times --> 6108.20 Mbps in 1964.58 usec 109: 2097149 bytes 16 times --> 6128.72 Mbps in 2610.65 usec 110: 2097152 bytes 19 times --> 6271.35 Mbps in 2551.29 usec 111: 2097155 bytes 19 times --> 6273.55 Mbps in 2550.39 usec 112: 3145725 bytes 19 times --> 6146.28 Mbps in 3904.79 usec 113: 3145728 bytes 17 times --> 6288.29 Mbps in 3816.62 usec 114: 3145731 bytes 17 times --> 6234.73 Mbps in 3849.41 usec 115: 4194301 bytes 8 times --> 5852.76 Mbps in 5467.50 usec 116: 4194304 bytes 9 times --> 5886.74 Mbps in 5435.94 usec 117: 4194307 bytes 9 times --> 5887.35 Mbps in 5435.39 usec 118: 6291453 bytes 9 times --> 4502.11 Mbps in 10661.67 usec 119: 6291456 bytes 6 times --> 4541.26 Mbps in 10569.75 usec 120: 6291459 bytes 6 times --> 4465.98 Mbps in 10747.93 usec 121: 8388605 bytes 3 times --> 4601.84 Mbps in 13907.47 usec 122: 8388608 bytes 3 times --> 4590.50 Mbps in 13941.84 usec 123: 8388611 bytes 3 times --> 4195.17 Mbps in 15255.65 usec vhost_net activated for both hosts: NPtcp -h 192.168.7.81 Send and receive buffers are 16384 and 87380 bytes (A bug in Linux doubles the requested buffer sizes) Now starting the main loop 0: 1 bytes 1013 times --> 0.10 Mbps in 75.89 usec 1: 2 bytes 1317 times --> 0.21 Mbps in 74.03 usec 2: 3 bytes 1350 times --> 0.30 Mbps in 76.90 usec 3: 4 bytes 866 times --> 0.43 Mbps in 71.27 usec 4: 6 bytes 1052 times --> 0.60 Mbps in 76.02 usec 5: 8 bytes 657 times --> 0.79 Mbps in 76.88 usec 6: 12 bytes 812 times --> 1.24 Mbps in 73.72 usec 7: 13 bytes 565 times --> 1.40 Mbps in 70.60 usec 8: 16 bytes 653 times --> 1.58 Mbps in 77.05 usec 9: 19 bytes 730 times --> 1.90 Mbps in 76.25 usec 10: 21 bytes 828 times --> 1.98 Mbps in 80.85 usec 11: 24 bytes 824 times --> 2.47 Mbps in 74.22 usec 12: 27 bytes 954 times --> 2.73 Mbps in 75.45 usec 13: 29 bytes 589 times --> 3.06 Mbps in 72.23 usec 14: 32 bytes 668 times --> 3.26 Mbps in 74.84 usec 15: 35 bytes 709 times --> 3.46 Mbps in 77.09 usec 16: 45 bytes 741 times --> 4.50 Mbps in 76.35 usec 17: 48 bytes 873 times --> 4.83 Mbps in 75.90 usec 18: 51 bytes 905 times --> 5.50 Mbps in 70.72 usec 19: 61 bytes 554 times --> 6.36 Mbps in 73.14 usec 20: 64 bytes 672 times --> 6.28 Mbps in 77.77 usec 21: 67 bytes 663 times --> 6.39 Mbps in 80.06 usec 22: 93 bytes 671 times --> 9.44 Mbps in 75.15 usec 23: 96 bytes 887 times --> 9.52 Mbps in 76.90 usec 24: 99 bytes 880 times --> 10.55 Mbps in 71.57 usec 25: 125 bytes 508 times --> 12.63 Mbps in 75.49 usec 26: 128 bytes 657 times --> 12.30 Mbps in 79.38 usec 27: 131 bytes 639 times --> 12.72 Mbps in 78.57 usec 28: 189 bytes 660 times --> 18.36 Mbps in 78.55 usec 29: 192 bytes 848 times --> 18.84 Mbps in 77.75 usec 30: 195 bytes 864 times --> 18.91 Mbps in 78.69 usec 31: 253 bytes 443 times --> 24.04 Mbps in 80.28 usec 32: 256 bytes 620 times --> 26.61 Mbps in 73.40 usec 33: 259 bytes 686 times --> 26.09 Mbps in 75.75 usec 34: 381 bytes 672 times --> 40.04 Mbps in 72.59 usec 35: 384 bytes 918 times --> 39.67 Mbps in 73.86 usec 36: 387 bytes 906 times --> 40.68 Mbps in 72.58 usec 37: 509 bytes 469 times --> 51.70 Mbps in 75.11 usec 38: 512 bytes 664 times --> 51.55 Mbps in 75.77 usec 39: 515 bytes 662 times --> 49.61 Mbps in 79.19 usec 40: 765 bytes 637 times --> 75.91 Mbps in 76.89 usec 41: 768 bytes 867 times --> 76.03 Mbps in 77.07 usec 42: 771 bytes 866 times --> 76.21 Mbps in 77.19 usec 43: 1021 bytes 436 times --> 99.46 Mbps in 78.32 usec 44: 1024 bytes 637 times --> 100.04 Mbps in 78.10 usec 45: 1027 bytes 641 times --> 100.06 Mbps in 78.31 usec 46: 1533 bytes 641 times --> 113.15 Mbps in 103.36 usec 47: 1536 bytes 644 times --> 127.72 Mbps in 91.75 usec 48: 1539 bytes 727 times --> 102.87 Mbps in 114.14 usec 49: 2045 bytes 293 times --> 177.68 Mbps in 87.81 usec 50: 2048 bytes 569 times --> 103.58 Mbps in 150.85 usec 51: 2051 bytes 331 times --> 107.53 Mbps in 145.52 usec 52: 3069 bytes 344 times --> 204.05 Mbps in 114.75 usec 53: 3072 bytes 580 times --> 207.53 Mbps in 112.93 usec 54: 3075 bytes 590 times --> 211.37 Mbps in 110.99 usec 55: 4093 bytes 301 times --> 285.23 Mbps in 109.48 usec 56: 4096 bytes 456 times --> 317.27 Mbps in 98.50 usec 57: 4099 bytes 507 times --> 332.92 Mbps in 93.93 usec 58: 6141 bytes 532 times --> 462.96 Mbps in 101.20 usec 59: 6144 bytes 658 times --> 451.75 Mbps in 103.76 usec 60: 6147 bytes 642 times --> 478.19 Mbps in 98.07 usec 61: 8189 bytes 340 times --> 743.81 Mbps in 84.00 usec 62: 8192 bytes 595 times --> 695.89 Mbps in 89.81 usec 63: 8195 bytes 556 times --> 702.95 Mbps in 88.94 usec 64: 12285 bytes 562 times --> 945.94 Mbps in 99.08 usec 65: 12288 bytes 672 times --> 870.86 Mbps in 107.65 usec 66: 12291 bytes 619 times --> 954.94 Mbps in 98.20 usec 67: 16381 bytes 339 times --> 1003.02 Mbps in 124.60 usec 68: 16384 bytes 401 times --> 652.84 Mbps in 191.47 usec 69: 16387 bytes 261 times --> 872.02 Mbps in 143.37 usec 70: 24573 bytes 348 times --> 1105.61 Mbps in 169.57 usec 71: 24576 bytes 393 times --> 1037.52 Mbps in 180.72 usec 72: 24579 bytes 368 times --> 1066.39 Mbps in 175.85 usec 73: 32765 bytes 189 times --> 1271.24 Mbps in 196.64 usec 74: 32768 bytes 254 times --> 1253.73 Mbps in 199.41 usec 75: 32771 bytes 250 times --> 1101.71 Mbps in 226.94 usec 76: 49149 bytes 220 times --> 1704.99 Mbps in 219.93 usec 77: 49152 bytes 303 times --> 1678.17 Mbps in 223.46 usec 78: 49155 bytes 298 times --> 1648.32 Mbps in 227.52 usec 79: 65533 bytes 146 times --> 1940.36 Mbps in 257.67 usec 80: 65536 bytes 194 times --> 1785.37 Mbps in 280.05 usec 81: 65539 bytes 178 times --> 2079.85 Mbps in 240.41 usec 82: 98301 bytes 207 times --> 2840.36 Mbps in 264.04 usec 83: 98304 bytes 252 times --> 3441.30 Mbps in 217.94 usec 84: 98307 bytes 305 times --> 3575.33 Mbps in 209.78 usec 85: 131069 bytes 158 times --> 3145.83 Mbps in 317.87 usec 86: 131072 bytes 157 times --> 3283.65 Mbps in 304.54 usec 87: 131075 bytes 164 times --> 3610.07 Mbps in 277.01 usec 88: 196605 bytes 180 times --> 4921.05 Mbps in 304.81 usec 89: 196608 bytes 218 times --> 4953.98 Mbps in 302.79 usec 90: 196611 bytes 220 times --> 4841.76 Mbps in 309.81 usec 91: 262141 bytes 107 times --> 4546.37 Mbps in 439.91 usec 92: 262144 bytes 113 times --> 4730.30 Mbps in 422.81 usec 93: 262147 bytes 118 times --> 5211.50 Mbps in 383.77 usec 94: 393213 bytes 130 times --> 7191.67 Mbps in 417.15 usec 95: 393216 bytes 159 times --> 7423.89 Mbps in 404.10 usec 96: 393219 bytes 164 times --> 7321.70 Mbps in 409.74 usec 97: 524285 bytes 81 times --> 7631.75 Mbps in 524.12 usec 98: 524288 bytes 95 times --> 7287.79 Mbps in 548.86 usec 99: 524291 bytes 91 times --> 7253.28 Mbps in 551.48 usec 100: 786429 bytes 90 times --> 8451.33 Mbps in 709.94 usec 101: 786432 bytes 93 times --> 8755.43 Mbps in 685.29 usec 102: 786435 bytes 97 times --> 8740.15 Mbps in 686.49 usec 103: 1048573 bytes 48 times --> 9220.97 Mbps in 867.59 usec 104: 1048576 bytes 57 times --> 8512.15 Mbps in 939.83 usec 105: 1048579 bytes 53 times --> 8556.70 Mbps in 934.94 usec 106: 1572861 bytes 53 times --> 9566.40 Mbps in 1254.39 usec 107: 1572864 bytes 53 times --> 10165.18 Mbps in 1180.50 usec 108: 1572867 bytes 56 times --> 11420.63 Mbps in 1050.73 usec 109: 2097149 bytes 31 times --> 11295.29 Mbps in 1416.52 usec 110: 2097152 bytes 35 times --> 11869.30 Mbps in 1348.02 usec 111: 2097155 bytes 37 times --> 11407.22 Mbps in 1402.62 usec 112: 3145725 bytes 35 times --> 12821.47 Mbps in 1871.86 usec 113: 3145728 bytes 35 times --> 11727.57 Mbps in 2046.46 usec 114: 3145731 bytes 32 times --> 12803.10 Mbps in 1874.55 usec 115: 4194301 bytes 17 times --> 10009.28 Mbps in 3197.03 usec 116: 4194304 bytes 15 times --> 10283.54 Mbps in 3111.77 usec 117: 4194307 bytes 16 times --> 10923.95 Mbps in 2929.34 usec 118: 6291453 bytes 17 times --> 11959.10 Mbps in 4013.68 usec 119: 6291456 bytes 16 times --> 10674.76 Mbps in 4496.59 usec 120: 6291459 bytes 14 times --> 10868.07 Mbps in 4416.61 usec 121: 8388605 bytes 7 times --> 9456.16 Mbps in 6768.07 usec 122: 8388608 bytes 7 times --> 9303.58 Mbps in 6879.07 usec 123: 8388611 bytes 7 times --> 10048.79 Mbps in 6368.93 usec so the case vhost_net is indeed faster in NPtcp by a factor almost 2, but that's only visible for the very high speeds and buffer sizes. Also note that the speed in the vhost_net case is much more variable, even if it's higher on average. I expected more difference... Actually I expected no-vhost to be slower than what it is. Kudos to the developers. If you have any more ideas for the slower boot please tell. I am of course not worried about waiting 10-30 more seconds at boot time, I am worried that if there is some factor 2x or 3x slowness somewhere, that can bite me in production without me even realizing. And after having seen the above no-vhost_net tcp benchmarks I guess I don't really need vhost_net active for these VMs during production, so I will just disable vhost_net to be on the safe side until I can track down the boot-time slowness somehow. Thanks for your help R.