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

To: ryanh@xxxxxxxxxx
Subject: Re: [Xen-devel] Hi,something about the xentrace tool
From: "rickey berkeley" <rickey.berkeley@xxxxxxxxx>
Date: Wed, 14 Jun 2006 01:11:32 +0800
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Hi folks
Thanks very much ! I've got it.You guys' direction and clue are very clear!
And I'd like to talk  another topic about the xentrace tool.

xentrace tool is some kind of user space tool.
Based on xentrace source code (tools/xentrace/xentrace.c),it will get, map and monitor the tracing data
from kernel space to the user space.I think xen use procfs to transfer data from kernel space to uesr space.

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.

On 6/12/06, Ryan Harper <ryanh@xxxxxxxxxx> wrote:
* rickey berkeley <rickey.berkeley@xxxxxxxxx> [2006-06-11 08:18]:
> Hi folks:

Search for TRACE_ , there are macros that wrap the proper call to trace
based on the number of fields that the trace record is using.

> Can someone give me a clue about this?
> Or are those interfaces (d1...d5) for developers to define their own
> interest to track the event?

Let's look at one of the trace macros:

0x0002f001  CPU%(cpu)d  %(tsc)d     sched_add_domain  [ domid =
0x%(1)08x, edomid = 0x%(2)08x ]

Ryan Harper
Software Engineer; Linux Technology Center
IBM Corp., Austin, Tx
(512) 838-9253   T/L: 678-9253

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