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The canonical location for the tracefs filesystem is at /sys/kernel/tracing.
But, from Documentation/trace/ftrace.rst:
Before 4.1, all ftrace tracing control files were within the debugfs
file system, which is typically located at /sys/kernel/debug/tracing.
For backward compatibility, when mounting the debugfs file system,
the tracefs file system will be automatically mounted at:
/sys/kernel/debug/tracing
A few spots in tools/virtio still refer to this older debugfs
path, so let's update them to avoid confusion.
Signed-off-by: Ross Zwisler <zwisler@google.com>
Message-Id: <20230215223350.2658616-6-zwisler@google.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Mukesh Ojha <quic_mojha@quicinc.com>
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We need to have a unique chardev for each data path, else the chardevs
will collide and qemu will die with this message:
qemu-system-x86_64: -device
virtserialport,bus=virtio-serial0.0,nr=2,chardev=charchannel0,
id=channel1,name=trace-path-cpu0:
Property 'virtserialport.chardev' can't take value 'charchannel0':
Device 'charchannel0' is in use
Signed-off-by: Ross Zwisler <zwisler@google.com>
Message-Id: <20230215223350.2658616-7-zwisler@google.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
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This patch adds a user tool, "trace agent" for sending trace data of a guest to
a Host in low overhead. This agent has the following functions:
- splice a page of ring-buffer to read_pipe without memory copying
- splice the page from write_pipe to virtio-console without memory copying
- write trace data to stdout by using -o option
- controlled by start/stop orders from a Host
Changes in v2:
- Cleanup (change fprintf() to pr_err() and an include guard)
Signed-off-by: Yoshihiro YUNOMAE <yoshihiro.yunomae.ez@hitachi.com>
Acked-by: Amit Shah <amit.shah@redhat.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
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