On Mon, Jul 10, 2017 at 01:24:23PM +0800, Xie Changlong wrote: > 在 7/9/2017 5:57 PM, Wang Dong 写道: > > Hi, > > > > I am new to QEMU. But I got some problem so that I want to figure it out. > > > > So I try to debug qemu to see what happened. > > > > And I found trace framework. I think this will help me understand the > > point. > > > > So I compiled qemu with option: > > > > ## *--enable-trace-backends=simple* > > > > And did as the docs/tracing.txt tell. But when I execute the example > > command in it, nothing just happens. > > > > *./scripts/simpletrace.py trace-events-all trace-xxxxxx(my trace file > > produced by qemu) > > I am not sure what happened. Just ask this. > > Any clue will be appreciated. Thanks in advance. > > * > > > > Did you set *trace-event*? I've encountered this issue in the past :) > (qemu) help trace-event > trace-event name on|off -- changes status of a specific trace event > (qemu) info trace-events
Yes, you need to enable specific trace events that you are interested in. 'trace-event' does that from the QEMU monitor at runtime. If you'd rather keep a file with a list of events to enable: $ echo bdrv_aio_readv > /tmp/events $ echo bdrv_aio_writev >> /tmp/events $ qemu -trace events=/tmp/events ... # your normal QEMU invocation It's hard to know what is missing without seeing your QEMU command-line and monitor commands you used. Stefan
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