Lines Matching +full:write +full:- +full:to +full:- +full:read

1 Trace Agent for virtio-trace
4 Trace agent is a user tool for sending trace data of a guest to a Host in low
6  - splice a page of ring-buffer to read_pipe without memory copying
7  - splice the page from write_pipe to virtio-console without memory copying
8  - write trace data to stdout by using -o option
9  - controlled by start/stop orders from a Host
13  2) Create a read/write thread per CPU. Each thread is bound to a CPU.
14     The read/write threads hold it.
17     the controller wake read/write threads.
18  5) The read/write threads start to read trace data from ring-buffers and
19     write the data to virtio-serial.
20  6) If the controller receives a stop order from a host, the read/write threads
21     stop to read trace data.
28 Makefile: Makefile of trace agent for virtio-trace
29 trace-agent.c: includes main function, sets up for operating trace agent
30 trace-agent.h: includes all structures and some macros
31 trace-agent-ctl.c: includes controller function for read/write threads
32 trace-agent-rw.c: includes read/write threads function
38 To use this trace agent for virtio-trace, we need to prepare some virtio-serial
42  virtio-trace uses virtio-serial pipe as trace data paths as to the number
44 	# mkdir /tmp/virtio-trace/
45 	# mkfifo /tmp/virtio-trace/trace-path-cpu{0,1,2,...,X}.{in,out}
46 	# mkfifo /tmp/virtio-trace/agent-ctl-path.{in,out}
49 	trace-path-cpu{0,1,2}.{in.out}
51 	agent-ctl-path.{in,out}.
53 2) Set up of virtio-serial pipe in a host
54  Add qemu option to use virtio-serial pipe.
56  ##virtio-serial device##
57      -device virtio-serial-pci,id=virtio-serial0\
59      -chardev pipe,id=charchannel0,path=/tmp/virtio-trace/agent-ctl-path\
60      -device virtserialport,bus=virtio-serial0.0,nr=1,chardev=charchannel0,\
61       id=channel0,name=agent-ctl-path\
63      -chardev pipe,id=charchannel1,path=/tmp/virtio-trace/trace-path-cpu0\
64      -device virtserialport,bus=virtio-serial0.0,nr=2,chardev=charchannel1,\
65       id=channel1,name=trace-path-cpu0\
68 If you manage guests with libvirt, add the following tags to domain XML files.
69 Then, libvirt passes the same command option to qemu.
72 	   <source path='/tmp/virtio-trace/agent-ctl-path'/>
73 	   <target type='virtio' name='agent-ctl-path'/>
74 	   <address type='virtio-serial' controller='0' bus='0' port='0'/>
77 	   <source path='/tmp/virtio-trace/trace-path-cpu0'/>
78 	   <target type='virtio' name='trace-path-cpu0'/>
79 	   <address type='virtio-serial' controller='0' bus='0' port='1'/>
82 Here, chardev names are restricted to trace-path-cpuX and agent-ctl-path. For
83 example, if a guest use three CPUs, chardev names should be trace-path-cpu0,
84 trace-path-cpu1, trace-path-cpu2, and agent-ctl-path.
87  You can find some chardev in /dev/virtio-ports/ in the guest.
102 	# ./trace-agent
103 read/write threads in the agent wait for start order from host. If you add -o
107 	# cat /tmp/virtio-trace/trace-path-cpu0.out
112 4) Start to read trace data by ordering from a host
113  A host injects read start order to the guest via virtio-serial.
114 	# echo 1 > /tmp/virtio-trace/agent-ctl-path.in
116 5) Stop to read trace data by ordering from a host
117  A host injects read stop order to the guest via virtio-serial.
118 	# echo 0 > /tmp/virtio-trace/agent-ctl-path.in