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[Qemu-devel] Static tracepoint control via trace-event
From: |
Jan Kiszka |
Subject: |
[Qemu-devel] Static tracepoint control via trace-event |
Date: |
Tue, 19 Oct 2010 15:08:08 +0200 |
User-agent: |
Mozilla/5.0 (X11; U; Linux i686 (x86_64); de; rv:1.8.1.12) Gecko/20080226 SUSE/2.0.0.12-1.1 Thunderbird/2.0.0.12 Mnenhy/0.7.5.666 |
Hi Stefan,
just had a closer look at qemu's new tracing framework. Looks cool,
though it leaves a bit room for improvements. ;)
One quirk I stumbled over quickly was the "disable" tag in trace-events.
It confused me first as qemu starts without any tracepoint enabled by
default and I thought I had to hack the file. Then I read the doc and
wondered which exiting or future backend would come without sufficiently
fast dynamic tracepoint control. Do you have any in mind?
Instead of making it a compile-time switch (except for simpletrace), I
would vote for declaring the simpletrace usage as the only one: disable
sets the default state of the dynamic tracepoint. That way we could use
trace-events to define a useful set of standard, moderate-impact
tracepoints that shall be on. Others will still be available once a
backend is configured, but remain off until enabled during runtime.
Anything else looks like overkill to me.
There are a few more things I have in mind (ftrace backend, enhanced
"-trace" switch, wildcards for enabling tracepoints, and more
tracepoints). Will hopefully come up with patches to address them, but
this may take a while.
Jan
PS: Do you maintain a tracing git tree?
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