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Re: [Xen-devel] Hi,something about the xentrace tool

rickey berkeley wrote:
Based on trace source code(xen/common/trace.c),dom0 tracing the event which are enabled.

xen initialize tracing buffer for each cpu,trace buffer size (in pages) in kenel space is defined by opt_tbuf_size.
The tracing buf use loop structure.

I guess when the tracing data increase rapidly ,and xentrace tool in user space does not take them immediately. Some tracing data will lost.Maybe relayfs or something else can solve this problem.

I added a basic flow control mechanism to the trace buffer system a few months ago. You can see an example of how to use it in tools/xenmon. The way it works is that as trace records are generated, a software interrupt is generated when the trace buffer gets filled to a certain point. The user space tools can use select() on an event channel to find out about these interrupts. See tools/xenmon/xenbaked.c for exact programming details. This code has not been copied into xentrace yet; Feel free to do so yourself if you think it's necessary.


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