[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-users] live migration time increases when using "mem-set"
Tim - What services are running on the dom-u's , and did you take any measures from within the dom-u's to clear idle child daemons out of cache? In other words lets use lighttpd with php as fastcgi for example. Lighttpd starts xx # of php children upon startup, and scales to the max # allowed during use. So if you had .. 30 children @ 15 MB each, and each one malloc()'ing an additional 10 MB of elbow room, then reduce ram suddenly and migrate, I would think those children would start paging dirty .. which would increase i/o wait and could explain it. If you did restart daemons that start idle children so the cache was freed prior to reducing memory allocated .. then I'm baffled too. HTH - Tim On Mon, 2006-09-04 at 16:48 -0400, Tim Wood wrote: > Hi, > I'm noticing very strange behavior when I create a VM, reduce its > memory allocation using "xm mem-set" and then live migrate it. > > I would expect reducing the memory allocation would make the migration > occur faster, but instead I am seeing the opposite. > > For example, if I create a VM with 900MB of ram initially, these are > the times I measure for different reduced memory allocations: > > RAM (MB) - Migration length (sec) > 900 - 11 > 768 - 20 > 512 - 33 > 450 - 38 > 256 - 51 > 128 - 55 > > Just the opposite of what I would expect! > > As reference, if a VM is created with 256 MB of ram and migrated, that > takes about 4 seconds. > > The VM is idle and so is the gigabit network. > > Looking at the xend.log files it looks like I am getting hundreds of > lines like this: > ERROR (XendCheckpoint:227) netbuf race: iter 4, pfn 28f78. mfn ffffffff > > I am using xen-testing... I'm very curious if this still occurs in > xen-unstable but can't test that myself right now. > > -Tim > > _______________________________________________ > Xen-users mailing list > Xen-users@xxxxxxxxxxxxxxxxxxx > http://lists.xensource.com/xen-users > > _______________________________________________ Xen-users mailing list Xen-users@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-users
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