[Xen-devel] synchronization between domUs

[Lei Ye <leiye.xen@xxxxxxxxx>]

Hi all,
 
I am doing the tracing work in Xen. I run two DomUs, and both have the same built xen 2.6.18.8 kernel. Each domain U has a filesystem image file mounted as root and run X11 GUI mode. I modfiy the kernel source code and direct the two domU logs to remote syslog server via printk/syslog. The problem I found is that multiple domainUs are to some extents time-correlated if both are idle, for example, the crond daemons execute the scripts almost at the same period although the domUs boots at different time. Can someone tell whether there is explicit synchronization done for DomUs in Xen? Why are they synchronized, like some system daemons?

Another problem is because I use the kernel ring buffer to cache the log information from kernel, some log in the kernel ring buffer has been wrapped by new log so that some log can't be written to log file. The default kernel buffer size config is 16KB, and I tried to increase it to 128KB. However, log missing problem is still there. Especially running I/O benchmarks, the trace missing problem is more severe. These tracing log records the I/O activity within the domU kernels, covering read and write paths. Does someone have alternative ideas for this problem.

Your answers are appreciated.

Alex

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