Avi Kivity wrote: > Liu, Eric E wrote: >> Hi, >> The following patches port xentrace to kvm which is useful for >> performance tuning and debugging. >> >> It is designed to allow debugging traces of kvm to be generated on >> Up/Smp machines. Each trace entry is outputted in a trace ring buffer >> for per cpu which is mapped to userspace, and the userspace tools can >> analyze the data according to some formats definitions. >> >> Since we already have had debugfs_entries and some other kernel debug >> mechanism to use, does this kvmtrace make sense? Any comment is >> welcomed. >> > > This looks very useful. While kvm_stat provides good data, this is much > more in depth. > > The kernel already contains a method of transferring percpu data to > userspace; see Documentation/filesystems/relay.txt. It supports mmap() > and read(). Please see if it is a good fit.
I would also suggest to use the new kernel standard for instrumentation: trace_mark(). This would also allow to reuse the trace points with other tracer and maybe even obsolete a separate transportation channel, e.g. when LTTng is once :-/ merged. Jan
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