xen-devel
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.
Rob
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