From: "Steven Rostedt (Google)" <rostedt@xxxxxxxxxxx> Update the man pages to describe the tracefs_cpu_pipe() function. Signed-off-by: Steven Rostedt (Google) <rostedt@xxxxxxxxxxx> --- Documentation/libtracefs-cpu.txt | 12 +++++++++++- Documentation/libtracefs.txt | 1 + 2 files changed, 12 insertions(+), 1 deletion(-) diff --git a/Documentation/libtracefs-cpu.txt b/Documentation/libtracefs-cpu.txt index 8975e6ec5a0b..d6215d9912c0 100644 --- a/Documentation/libtracefs-cpu.txt +++ b/Documentation/libtracefs-cpu.txt @@ -4,7 +4,8 @@ libtracefs(3) NAME ---- tracefs_cpu_read_size, tracefs_cpu_read, tracefs_cpu_buffered_read, tracefs_cpu_write, -tracefs_cpu_stop, tracefs_cpu_flush, tracefs_cpu_flush_write - Reading trace_pipe_raw data +tracefs_cpu_stop, tracefs_cpu_flush, tracefs_cpu_flush_write, tracefs_cpu_pipe +- Reading trace_pipe_raw data SYNOPSIS -------- @@ -19,6 +20,7 @@ int *tracefs_cpu_write*(struct tracefs_cpu pass:[*]_tcpu_, int _wfd_, bool _nonb int *tracefs_cpu_stop*(struct tracefs_cpu pass:[*]_tcpu_); int *tracefs_cpu_flush*(struct tracefs_cpu pass:[*]_tcpu_, void pass:[*]_buffer_); int *tracefs_cpu_flush_write*(struct tracefs_cpu pass:[*]_tcpu_, int _wfd_); +int *tracefs_cpu_pipe*(struct tracefs_cpu pass:[*]_tcpu_, int _wfd_, bool _nonblock_); -- DESCRIPTION @@ -66,6 +68,14 @@ trace_pipe_raw into non-blocking mode. The *tracefs_cpu_flush_write()* same as *trace_cpu_flush()* except it takes a file descriptor _wfd_ to flush the data into. +The *tracefs_cpu_pipe()* is similar to *tracefs_cpu_write()* but the _wfd_ file descriptor +must be a pipe. This call is an optimization of *tracefs_cpu_write()* that uses two calls +to *splice*(2) in order to connect the trace_pipe_raw file descriptor with the write file +descriptor. *splice*(2) requires that one of the passed in file descriptors is a pipe. +If the application wants to pass the data to an existing pipe, there's no reason for +there to be two *splice*(2) system calls and *tracefs_cpu_pipe()* can simply use a single +call to _wfd_. + RETURN VALUE ------------ The *tracefs_cpu_open()* returns a struct tracefs_cpu descriptor that can be diff --git a/Documentation/libtracefs.txt b/Documentation/libtracefs.txt index 50af23e33026..0081210f8951 100644 --- a/Documentation/libtracefs.txt +++ b/Documentation/libtracefs.txt @@ -280,6 +280,7 @@ Recording of trace_pipe_raw files: int *tracefs_cpu_stop*(struct tracefs_cpu pass:[*]_tcpu_); int *tracefs_cpu_flush*(struct tracefs_cpu pass:[*]_tcpu_, void pass:[*]_buffer_); int *tracefs_cpu_flush_write*(struct tracefs_cpu pass:[*]_tcpu_, int _wfd_); + int *tracefs_cpu_pipe*(struct tracefs_cpu pass:[*]_tcpu_, int _wfd_, bool _nonblock_); -- -- 2.35.1
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