Re: [libvirt] [PATCH 00/13] Add multiple trace backend function and add new ftrace backend for libvirt

From: Xinghai Yu <yuxinghai(a)cn.fujitsu.com&gt; This patch set will let libvirt to support multiple trace backend function and add a new 'ftrace' backend at the same time. Then, libvirt would have 2 trace backend: dtrace, ftrace.They can be used alone or together. Patchs 1,2,3,4,5 are used for supporting multiple trace backend function. Patch 6 are used for adding ftrace as a new trace backend for libvirt. Patchs 7,8,9,10,11,12,13 add ftrace initial code in programs who use it. Thanks very much for Stefan Hajnoczi for I have used his scripts in patch 4 which commited in qemu. Thanks very much for Eiichi Tsukata for I have used his ftrace codes in patch 6 which commited in qemu. Backgroud: The existing trace mechanism in libvirt is dtrace. Although the dtrace can work, it's not work well enough. Every time we want get information from the trace point we must write a systemtap script and run it together with libvirt. That's really unpractical on some occasion, especially on production server since the systemtap script can't be executed automatically. And some problems may be not easy to reproduce, then it will cost a lot of time to get the trace information again. So I think it is essential to add supporting for record the trace information automatically in libvirt to satisfy the user's requirement. That's why I implemented multiple trace backend function and ftrace support in libvirt.