Bugs item #2005957, was opened at 2008-06-29 19:12 Message generated for change (Comment added) made by andyz You can respond by visiting: https://sourceforge.net/tracker/?func=detail&atid=893831&aid=2005957&group_id=180599
Please note that this message will contain a full copy of the comment thread, including the initial issue submission, for this request, not just the latest update. Category: qemu Group: None Status: Open Resolution: None Priority: 5 Private: No Submitted By: Andrew Zabolotny (andyz) Assigned to: Nobody/Anonymous (nobody) Summary: TAP networking stalls on large file transfers Initial Comment: System: Fedora 9 KVM version: tried 65 and 70, both exhibit the same behaviour When using TAP networking if I copy a large file from host to guest OS, I get extremely low performance (under 1 megabyte/s) and sometimes file transfer stalls. If I run tcpdump in guest OS (even with a bogus filter - e.g. tcpdump -nn -i eth0 host 1.2.3.4) the stalled connection suddenly come alive. If I run repeatedly tcpdump/press Ctrl+C and so on, the file transfer visually goes much faster. I found a old thread about the same bug in QEMU: http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=290569 The patch proposed there was applied in QEMU 0.7.3, but when I looked into QEMU 0.9.1 sources - it is not there, so it seems it was removed for some reason. However, if I run the same virtual machine with QEMU, I get stable performance with about 8-9 megabytes per second flowing both ways (from host to guest and from guest to host). I tried to apply the patch on KVM 70, but it does not make any difference :-( The guest OS is Ubuntu 8.04 but I guess that does not matter. I will be glad to cooperate to find/fix the bug but for now I'm out of ideas :-( ---------------------------------------------------------------------- >Comment By: Andrew Zabolotny (andyz) Date: 2008-06-29 20:09 Message: Logged In: YES user_id=1815 Originator: YES Update: I was advised on irc to try e1000 network card emulation instead, and with it I get very good results - 32 megabytes per second and more. So the bug occurs only with rtl8139 emulation, perhaps because of bandwidth limitation (packets aren't read quick enough from the TAP handle)? ---------------------------------------------------------------------- You can respond by visiting: https://sourceforge.net/tracker/?func=detail&atid=893831&aid=2005957&group_id=180599 -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
