[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] RE: [Xen-devel] Xend crashes, how to debug?
The observation that speeding up xenstore reduces the frequency of crashes is interesting. Perhaps the failure happens when a concurrent transaction causes an abort? Maybe you could provoke it by running 'xm create' in a loop while also writing somewhere in xenstore? IIRC (although I could be mistaken) the standard C xenstore considers all concurrent transactions to be conflicting even if they operate on disjoint parts of the tree so provoking an abort would be easy. > And XenServer is opensource now.. so you could always try the ocaml > xend. > > Althought I'm not sure if it's easy/direct replacement.. Sorry, couldn't resist: <begin advert> Feel free to give it a go. Although it's still in development (it's in a bit of a stabilization phase atm) mysterious toolstack crashes / segfaults are rare (famous last words?). The kind of bugs it's currently suffering from are mostly to do with the new functionality we've been integrating recently e.g. RBAC, ballooning etc. For more normal stuff it ought to be pretty good. Caveats: 1. We don't have an 'xm'... instead there's a CLI called 'xe' which can do almost everything the API can do but the syntax is different to 'xm'. You'd either have to port your scripts ('xe vm-start' rather than 'xm create'?) or write some kind of wrapper. 2. It's much easier to install and use the whole integrated patched xen + patched qemu + dom0 + toolstack rather than transplant the toolstack onto another dom0. I'm sure it's possible but we've been focusing dev + test on the single environment. http://www.xen.org/products/cloud_source.html <end advert> FWIW we also use an ocaml xenstore which handles concurrent transactions efficiently. There are some performance graphs here: http://thomas.gazagnaire.com/pub/GH09.pdf The reason we rewrote xenstored was because we used xenstore to report periodic guest performance stats to dom0. By doing this we accidentally created a horrible scalability bottleneck where, somewhere around 30 or 40 guests, every transaction aborted and the system livelocked. The new xenstored is smart enough to realize that these separate transactions are not conflicting and can be committed together. Cheers, Dave _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-devel
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