Laurent Vivier wrote: > Le mercredi 23 avril 2008 à 19:25 +0300, Avi Kivity a écrit : > >> Laurent Vivier wrote: >> >>> Le mercredi 23 avril 2008 à 10:10 -0500, Anthony Liguori a écrit : >>> [...] >>> >>> >>>> The ne2k is pretty mmio heavy. You should be able to observe a boost >>>> with something like iperf (guest=>host) I would think if this is a real >>>> savings. >>>> >>>> >>> I like your advices :-D >>> >>> I use iperf with e1000 emulation and a slightly modified patch (to >>> detect MMIO write in a loop), server is on the host, client on the >>> guest, with default values. >>> >>> RESULT WITHOUT BATCHING: >>> >>> [ 4] 0.0-10.0 sec 235 MBytes 197 Mbits/sec >>> [ 5] 0.0-10.0 sec 194 MBytes 163 Mbits/sec >>> [ 4] 0.0-10.0 sec 185 MBytes 155 Mbits/sec >>> [ 5] 0.0-10.0 sec 227 MBytes 190 Mbits/sec >>> [ 4] 0.0-10.0 sec 196 MBytes 164 Mbits/sec >>> [ 5] 0.0-10.0 sec 194 MBytes 163 Mbits/sec >>> [ 4] 0.0-10.0 sec 184 MBytes 154 Mbits/sec >>> >>> RESULT WITH BATCHING: >>> >>> ------------------------------------------------------------ >>> Server listening on TCP port 5001 >>> TCP window size: 85.3 KByte (default) >>> ------------------------------------------------------------ >>> [ 4] 0.0-10.0 sec 357 MBytes 299 Mbits/sec >>> [ 5] 0.0-10.1 sec 418 MBytes 347 Mbits/sec >>> [ 4] 0.0-10.0 sec 408 MBytes 342 Mbits/sec >>> [ 5] 0.0-10.0 sec 422 MBytes 353 Mbits/sec >>> [ 4] 0.0-10.1 sec 436 MBytes 362 Mbits/sec >>> [ 5] 0.0-10.0 sec 416 MBytes 348 Mbits/sec >>> [ 4] 0.0-10.0 sec 431 MBytes 361 Mbits/sec >>> >>> Well, it's nice ? >>> >>> >> It's too good to be true. >> >> I think we're seeing two bugs cancel each other out, resulting in a >> performance gain. Linux doesn't know how to queue outgoing packets, so >> it bangs on the mmio that starts the transmit after every packet. mmio >> batching doesn't know that this mmio register is critical for latency, >> so it queues it up. The result is that you you get not just mmio >> batching, but also packet batching! Which dramatically improves >> performace at the expense of latency. >> > > How can I check that ? How can I measure latency ? >
ping (from guest to host) Regards, Anthony Liguori > Perhaps I can swap server and client between guest and host ? > > >> Sorry (if it's true :) >> >> > > Thank you for your help, > Laurent > ------------------------------------------------------------------------- This SF.net email is sponsored by the 2008 JavaOne(SM) Conference Don't miss this year's exciting event. There's still time to save $100. Use priority code J8TL2D2. http://ad.doubleclick.net/clk;198757673;13503038;p?http://java.sun.com/javaone _______________________________________________ kvm-devel mailing list kvm-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/kvm-devel
