Marco Tizzoni
2009-Sep-27 17:34 UTC
[Xen-devel] Sending packet at fixed rate - bad performance
Hi all, I''m doing some tests about i/o performance and cpu overhead in dom0. I''ve coded a small tool that can sends UDP packets at fixed rate or flood. While sending packet at fixed rate I''m experiencing performance problem, related to how Xen handle signal, I guess. On my laptop (Core2 duo P8700), with no Xen running, I can send packets at a rate of 20k, 40k, 60k, 80k/s achieving an actual packet rate per second pretty near to the requested rate. On Xen (dom0 with no guest running and no load - Athlon 64 dual core 4000+ ), the performance are really bad. Here what happen: Requested | Actual 10 | 10.03 100 | 100.05 200 | 200.04 500 | 250.04 1000 | 250.18 10000 | 247.49 20000 | 250.26 40000 | 250.24 It seems impossibile to go over 250 packets/second, but in flood configuration (send packet as fast as possible) the actual rate is higher, 39k packets/second about. The main difference is in the code. Flood loop as been implemented like this: ------------------ for (;;) send_pkt(); ------------------ while the fixed rate use setitimer to wake up send_pkt() when needed. Any idea of why this happen? bye, Marco _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel