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Re: [patch 1/3] Trace code and documentation
- From: Randy Dunlap <randy dot dunlap at oracle dot com>
- To: "David J. Wilder" <dwilder at us dot ibm dot com>
- Cc: linux-kernel at vger dot kernel dot org, akpm at linux-foundation dot org, hch at infradead dot org, systemtap at sources dot redhat dot com
- Date: Tue, 2 Oct 2007 10:05:57 -0700
- Subject: Re: [patch 1/3] Trace code and documentation
- Organization: Oracle Linux Eng.
- References: <1191342800.31351.9.camel@lc4eb748232119.ibm.com>
On Tue, 02 Oct 2007 09:33:19 -0700 David J. Wilder wrote:
> Trace - Provides tracing primitives
>
> Signed-off-by: Tom Zanussi <zanussi@us.ibm.com>
> Signed-off-by: Martin Hunt <hunt@redhat.com>
> Signed-off-by: David Wilder <dwilder@us.ibm.com>
> ---
> Documentation/trace.txt | 160 ++++++++++++++
> include/linux/trace.h | 99 +++++++++
> lib/Kconfig | 9 +
> lib/Makefile | 2 +
> lib/trace.c | 563 +++++++++++++++++++++++++++++++++++++++++++++++
> 5 files changed, 833 insertions(+), 0 deletions(-)
>
> diff --git a/Documentation/trace.txt b/Documentation/trace.txt
> new file mode 100644
> index 0000000..195132d
> --- /dev/null
> +++ b/Documentation/trace.txt
> +Trace User Interface
> +===================
> +When a trace channel is created and started, the following
> +directories and files are created in the root of the mounted debugfs.
> +
> +/debug (root of the debugfs)
> + /<trace-root-dir>
> + /<trace-name>
> + trace[0...N-1] Per-CPU trace data, one
> + file per CPU.
> +
> + state Start or stop tracing by
> + by writing the strings
> + "start" or "stop" to this
> + file. Read the file to get the
> + current state.
> +
> + dropped The number of records dropped
> + due to a full-buffer condition,
> + for non-TRACE_FLIGHT_CHANNELs
> + only.
> +
> + rewind Trigger a rewind by writing
> + to this file. i.e. start
> + next read at the beginning
> + again. Only available for
> + TRACE_FLIGHT_CHANNELS.
> +
> +
> + nr_sub Number of sub-buffers
> + in the channel.
> +
> + sub_size Size of sub-buffers in
> + the channnel.
> +
> +Trace data is gathered from the trace[0...N] files using one of the
trace[0..N-1]
> +available interfaces provided by relay.
> +
> +When using the read(2) interface, as data is read it is marked as
> +consumed by the relay subsystem. Therefore, subsequent reads will
> +only return unconsumed data.
---
~Randy