| Message ID | 20230130181915.1113313-8-zwisler@google.com (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | use canonical ftrace path whenever possible | expand |
On Mon, Jan 30, 2023 at 11:19:13AM -0700, Ross Zwisler wrote: > 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> > --- > tools/virtio/virtio-trace/README | 2 +- > tools/virtio/virtio-trace/trace-agent.c | 2 +- > 2 files changed, 2 insertions(+), 2 deletions(-) > > diff --git a/tools/virtio/virtio-trace/README b/tools/virtio/virtio-trace/README > index b64845b823ab..cea29a2a4c0a 100644 > --- a/tools/virtio/virtio-trace/README > +++ b/tools/virtio/virtio-trace/README > @@ -95,7 +95,7 @@ Run > > 1) Enable ftrace in the guest > <Example> > - # echo 1 > /sys/kernel/debug/tracing/events/sched/enable > + # echo 1 > /sys/kernel/tracing/events/sched/enable > > 2) Run trace agent in the guest > This agent must be operated as root. > diff --git a/tools/virtio/virtio-trace/trace-agent.c b/tools/virtio/virtio-trace/trace-agent.c > index cdfe77c2b4c8..805942d02e9f 100644 > --- a/tools/virtio/virtio-trace/trace-agent.c > +++ b/tools/virtio/virtio-trace/trace-agent.c > @@ -19,7 +19,7 @@ > #define PIPE_MIN_SIZE (PAGE_SIZE*PIPE_DEF_BUFS) > #define PIPE_MAX_SIZE (1024*1024) > #define READ_PATH_FMT \ > - "/sys/kernel/debug/tracing/per_cpu/cpu%d/trace_pipe_raw" > + "/sys/kernel/tracing/per_cpu/cpu%d/trace_pipe_raw" Should we try both old and new path then? > #define WRITE_PATH_FMT "/dev/virtio-ports/trace-path-cpu%d" > #define CTL_PATH "/dev/virtio-ports/agent-ctl-path" > > -- > 2.39.1.456.gfc5497dd1b-goog
On Mon, Jan 30, 2023 at 02:26:43PM -0500, Michael S. Tsirkin wrote: > On Mon, Jan 30, 2023 at 11:19:13AM -0700, Ross Zwisler wrote: > > 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> > > --- > > tools/virtio/virtio-trace/README | 2 +- > > tools/virtio/virtio-trace/trace-agent.c | 2 +- > > 2 files changed, 2 insertions(+), 2 deletions(-) > > > > diff --git a/tools/virtio/virtio-trace/README b/tools/virtio/virtio-trace/README > > index b64845b823ab..cea29a2a4c0a 100644 > > --- a/tools/virtio/virtio-trace/README > > +++ b/tools/virtio/virtio-trace/README > > @@ -95,7 +95,7 @@ Run > > > > 1) Enable ftrace in the guest > > <Example> > > - # echo 1 > /sys/kernel/debug/tracing/events/sched/enable > > + # echo 1 > /sys/kernel/tracing/events/sched/enable > > > > 2) Run trace agent in the guest > > This agent must be operated as root. > > diff --git a/tools/virtio/virtio-trace/trace-agent.c b/tools/virtio/virtio-trace/trace-agent.c > > index cdfe77c2b4c8..805942d02e9f 100644 > > --- a/tools/virtio/virtio-trace/trace-agent.c > > +++ b/tools/virtio/virtio-trace/trace-agent.c > > @@ -19,7 +19,7 @@ > > #define PIPE_MIN_SIZE (PAGE_SIZE*PIPE_DEF_BUFS) > > #define PIPE_MAX_SIZE (1024*1024) > > #define READ_PATH_FMT \ > > - "/sys/kernel/debug/tracing/per_cpu/cpu%d/trace_pipe_raw" > > + "/sys/kernel/tracing/per_cpu/cpu%d/trace_pipe_raw" > > Should we try both old and new path then? Sure, I think it makes sense to have all the comments & documentation point only to the preferred location, but I think for tools it makes sense to check both places so that we don't see field regressions. This is what the BPF code does: https://elixir.bootlin.com/linux/latest/source/tools/bpf/bpftool/tracelog.c#L98 I'll add a check and fallback to this tool & send out v2. Thanks for the review. > > #define WRITE_PATH_FMT "/dev/virtio-ports/trace-path-cpu%d" > > #define CTL_PATH "/dev/virtio-ports/agent-ctl-path" > > > > -- > > 2.39.1.456.gfc5497dd1b-goog >
diff --git a/tools/virtio/virtio-trace/README b/tools/virtio/virtio-trace/README index b64845b823ab..cea29a2a4c0a 100644 --- a/tools/virtio/virtio-trace/README +++ b/tools/virtio/virtio-trace/README @@ -95,7 +95,7 @@ Run 1) Enable ftrace in the guest <Example> - # echo 1 > /sys/kernel/debug/tracing/events/sched/enable + # echo 1 > /sys/kernel/tracing/events/sched/enable 2) Run trace agent in the guest This agent must be operated as root. diff --git a/tools/virtio/virtio-trace/trace-agent.c b/tools/virtio/virtio-trace/trace-agent.c index cdfe77c2b4c8..805942d02e9f 100644 --- a/tools/virtio/virtio-trace/trace-agent.c +++ b/tools/virtio/virtio-trace/trace-agent.c @@ -19,7 +19,7 @@ #define PIPE_MIN_SIZE (PAGE_SIZE*PIPE_DEF_BUFS) #define PIPE_MAX_SIZE (1024*1024) #define READ_PATH_FMT \ - "/sys/kernel/debug/tracing/per_cpu/cpu%d/trace_pipe_raw" + "/sys/kernel/tracing/per_cpu/cpu%d/trace_pipe_raw" #define WRITE_PATH_FMT "/dev/virtio-ports/trace-path-cpu%d" #define CTL_PATH "/dev/virtio-ports/agent-ctl-path"
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> --- tools/virtio/virtio-trace/README | 2 +- tools/virtio/virtio-trace/trace-agent.c | 2 +- 2 files changed, 2 insertions(+), 2 deletions(-)