Message-ID: <4B932672.3010309@xenotime.net>
Date:	Sat, 06 Mar 2010 20:07:14 -0800
From:	Randy Dunlap <rdunlap@...otime.net>
To:	William Cohen <wcohen@...hat.com>
CC:	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Add DocBook documentation for the block tracepoints.

William Cohen wrote:
> This patch adds a simple description of the various block tracepoints
> available in the kernel.
> 
> Signed-off-by: William Cohen <wcohen@...hat.com>

Thanks.  I have just a few nits below then it will be ready IMO.

> ---
>  Documentation/DocBook/tracepoint.tmpl |   13 +++
>  include/trace/events/block.h          |  164 +++++++++++++++++++++++++++++++++
>  2 files changed, 177 insertions(+), 0 deletions(-)
> 
> diff --git a/Documentation/DocBook/tracepoint.tmpl b/Documentation/DocBook/tracepoint.tmpl
> index 8bca1d5..e8473ea 100644
> --- a/Documentation/DocBook/tracepoint.tmpl
> +++ b/Documentation/DocBook/tracepoint.tmpl
> @@ -16,6 +16,15 @@
>       </address>
>      </affiliation>
>     </author>
> +   <author>
> +    <firstname>William</firstname>
> +    <surname>Cohen</surname>
> +    <affiliation>
> +     <address>
> +      <email>wcohen@...hat.com</email>
> +     </address>
> +    </affiliation>
> +   </author>
>    </authorgroup>
>  
>    <legalnotice>
> @@ -91,4 +100,8 @@
>  !Iinclude/trace/events/signal.h
>    </chapter>
>  
> +  <chapter id="block">
> +   <title>Block IO</title>
> +!Iinclude/trace/events/block.h
> +  </chapter>
>  </book>
> diff --git a/include/trace/events/block.h b/include/trace/events/block.h
> index 5fb7273..6bb1181 100644
> --- a/include/trace/events/block.h
> +++ b/include/trace/events/block.h
> @@ -40,6 +40,16 @@ DECLARE_EVENT_CLASS(block_rq_with_error,
>  		  __entry->nr_sector, __entry->errors)
>  );
>  
> +/**
> + * block_rq_abort - abort block operation request
> + * @q: queue containing the block operation request
> + * @rq: block IO operation request
> + *
> + * Called immediately after pending block IO operation request @rq in
> + * queue @q is aborted. The fields in the operation request @rq
> + * can be examined to determine which device and sectors the pending
> + * operation would access.
> + */
>  DEFINE_EVENT(block_rq_with_error, block_rq_abort,
>  
>  	TP_PROTO(struct request_queue *q, struct request *rq),
> @@ -47,6 +57,15 @@ DEFINE_EVENT(block_rq_with_error, block_rq_abort,
>  	TP_ARGS(q, rq)
>  );
>  
> +/**
> + * block_rq_requeue - place block IO request back on a queue
> + * @q: queue holding operation
> + * @rq: block IO operation request
> + *
> + * The block operation request @rq is being placed back into queue
> + * @q.  For some reason the request was not completed and needs to be
> + * put back in the queue.
> + */
>  DEFINE_EVENT(block_rq_with_error, block_rq_requeue,
>  
>  	TP_PROTO(struct request_queue *q, struct request *rq),
> @@ -54,6 +73,17 @@ DEFINE_EVENT(block_rq_with_error, block_rq_requeue,
>  	TP_ARGS(q, rq)
>  );
>  
> +/**
> + * block_rq_complete - block IO operation completed by device driver
> + * @q: queue containing the block operation request
> + * @rq: block operations request
> + *
> + * The block_rq_complete tracepoint event indicates that some portion
> + * of operation request has been completed by the device driver.  If
> + * the @rq->bio is NULL, then there is absolutely no additonal work to

                      %NULL,                            additional

> + * do for the request. If @rq->bio is non-NULL then there is
> + * additional work is required to complete the request.

                      ^^drop "is"

> + */
>  DEFINE_EVENT(block_rq_with_error, block_rq_complete,
>  
>  	TP_PROTO(struct request_queue *q, struct request *rq),
> @@ -95,6 +125,16 @@ DECLARE_EVENT_CLASS(block_rq,
>  		  __entry->nr_sector, __entry->comm)
>  );
>  
> +/**
> + * block_rq_insert - insert block operation request into queue
> + * @q: target queue
> + * @rq: block IO operation request
> + *
> + * Called immediately before block operation request @rq is inserted
> + * into queue @q.  The fields in the operation request @rq struct can
> + * be examined to determine which device and sectors the pending
> + * operation would access.
> + */
>  DEFINE_EVENT(block_rq, block_rq_insert,
>  
>  	TP_PROTO(struct request_queue *q, struct request *rq),
> @@ -102,6 +142,14 @@ DEFINE_EVENT(block_rq, block_rq_insert,
>  	TP_ARGS(q, rq)
>  );
>  
> +/**
> + * block_rq_issue - issue pending block io request operation to device driver

                                           IO

> + * @q: queue holding operation
> + * @rq: block IO operation operation request
> + *
> + * Called when block operation request @rq from queue @q is sent to a
> + * device driver for processing.
> + */
>  DEFINE_EVENT(block_rq, block_rq_issue,
>  
>  	TP_PROTO(struct request_queue *q, struct request *rq),
> @@ -109,6 +157,17 @@ DEFINE_EVENT(block_rq, block_rq_issue,
>  	TP_ARGS(q, rq)
>  );
>  
> +/**
> + * block_bio_bounce - used bounce buffer when processing block operation
> + * @q: queue holding the block operation
> + * @bio: block operation
> + *
> + * A bounce buffer was used to handle the block operation @bio in @q.
> + * This occurs when hardware limitations prevent a direct transfer of
> + * data between the @bio data memory area and the IO device.  Use of a
> + * bounce buffer requires extra copying of data and decreases
> + * performance.
> + */
>  TRACE_EVENT(block_bio_bounce,
>  
>  	TP_PROTO(struct request_queue *q, struct bio *bio),
> @@ -138,6 +197,14 @@ TRACE_EVENT(block_bio_bounce,
>  		  __entry->nr_sector, __entry->comm)
>  );
>  
> +/**
> + * block_bio_complete - completed all work on the block operation
> + * @q: queue holding the block operation
> + * @bio: block operation completed
> + *
> + * This tracepoint indicates there is no further work to do on this
> + * block IO operation @bio.
> + */
>  TRACE_EVENT(block_bio_complete,
>  
>  	TP_PROTO(struct request_queue *q, struct bio *bio),
> @@ -193,6 +260,14 @@ DECLARE_EVENT_CLASS(block_bio,
>  		  __entry->nr_sector, __entry->comm)
>  );
>  
> +/**
> + * block_bio_backmerge - merging block operation to the end of an existing operation
> + * @q: queue holding operation
> + * @bio: new block operation to merge
> + *
> + * Merging block request @bio to the end of an existing block request
> + * in queue @q.
> + */
>  DEFINE_EVENT(block_bio, block_bio_backmerge,
>  
>  	TP_PROTO(struct request_queue *q, struct bio *bio),
> @@ -200,6 +275,14 @@ DEFINE_EVENT(block_bio, block_bio_backmerge,
>  	TP_ARGS(q, bio)
>  );
>  
> +/**
> + * block_bio_frontmerge - merging block operation to the beginning of an existing operation
> + * @q: queue holding operation
> + * @bio: new block operation to merge
> + *
> + * Merging block IO operation @bio to the beginning of an existing block
> + * operation in queue @q.
> + */
>  DEFINE_EVENT(block_bio, block_bio_frontmerge,
>  
>  	TP_PROTO(struct request_queue *q, struct bio *bio),
> @@ -207,6 +290,13 @@ DEFINE_EVENT(block_bio, block_bio_frontmerge,
>  	TP_ARGS(q, bio)
>  );
>  
> +/**
> + * block_bio_queue - putting new block IO operation in queue
> + * @q: queue holding operation
> + * @bio: new block operation
> + *
> + * About to  place the block IO operation @bio into queue @q.

            to place

> + */
>  DEFINE_EVENT(block_bio, block_bio_queue,
>  
>  	TP_PROTO(struct request_queue *q, struct bio *bio),
> @@ -243,6 +333,15 @@ DECLARE_EVENT_CLASS(block_get_rq,
>  		  __entry->nr_sector, __entry->comm)
>  );
>  
> +/**
> + * block_getrq - get a free request entry in queue for block IO operations
> + * @q: queue for operations
> + * @bio: pending block IO operation
> + * @rw: low bit indicates a read (%0) or a write (%1)
> + *
> + * A request struct for queue @q has been allocated to handle the
> + * block IO operation @bio.
> + */
>  DEFINE_EVENT(block_get_rq, block_getrq,
>  
>  	TP_PROTO(struct request_queue *q, struct bio *bio, int rw),
> @@ -250,6 +349,17 @@ DEFINE_EVENT(block_get_rq, block_getrq,
>  	TP_ARGS(q, bio, rw)
>  );
>  
> +/**
> + * block_sleeprq - waiting to get a free request entry in queue for block IO operation
> + * @q: queue for operation
> + * @bio: pending block IO operation
> + * @rw: low bit indicates a read (%0) or a write (%1)
> + *
> + * In the case where a request struct cannot be provided for queue @q
> + * the process needs to wait for an request struct to become
> + * available.  This tracepoint event is generated each time the
> + * process goes to sleep waiting for request struct become available.
> + */
>  DEFINE_EVENT(block_get_rq, block_sleeprq,
>  
>  	TP_PROTO(struct request_queue *q, struct bio *bio, int rw),
> @@ -257,6 +367,14 @@ DEFINE_EVENT(block_get_rq, block_sleeprq,
>  	TP_ARGS(q, bio, rw)
>  );
>  
> +/**
> + * block_plug - keep operations requests in request queue
> + * @q: request queue to plug
> + *
> + * Plug the request queue @q.  Do not allow block operation requests
> + * to be sent to the device driver. Instead, accumulate requests in
> + * the queue to improve throughput performance of the block device.
> + */
>  TRACE_EVENT(block_plug,
>  
>  	TP_PROTO(struct request_queue *q),
> @@ -293,6 +411,13 @@ DECLARE_EVENT_CLASS(block_unplug,
>  	TP_printk("[%s] %d", __entry->comm, __entry->nr_rq)
>  );
>  
> +/**
> + * block_unplug_timer - timed release of operations requests in queue to device driver
> + * @q: request queue to unplug
> + *
> + * Unplug the request queue @q because a timer expired and allow block
> + * operation requests to be sent to the device driver.
> + */
>  DEFINE_EVENT(block_unplug, block_unplug_timer,
>  
>  	TP_PROTO(struct request_queue *q),
> @@ -300,6 +425,13 @@ DEFINE_EVENT(block_unplug, block_unplug_timer,
>  	TP_ARGS(q)
>  );
>  
> +/**
> + * block_unplug_io - release of operations requests in request queue
> + * @q: request queue to unplug
> + *
> + * Unplug request queue @q because device driver is scheduled to work
> + * on elements in the request queue.
> + */
>  DEFINE_EVENT(block_unplug, block_unplug_io,
>  
>  	TP_PROTO(struct request_queue *q),
> @@ -307,6 +439,17 @@ DEFINE_EVENT(block_unplug, block_unplug_io,
>  	TP_ARGS(q)
>  );
>  
> +/**
> + * block_split - split a single bio struct into two bio structs
> + * @q: queue containing the bio
> + * @bio: block operation being split
> + * @new_sector: The starting sector for the new bio
> + *
> + * The bio request @bio in request queue @q needs to be split into two
> + * bio requests. The newly created @bio request starts at
> + * @new_sector. This split may be required due to hardware limitation
> + * such as operation crossing device boundaries in a RAID system.
> + */
>  TRACE_EVENT(block_split,
>  
>  	TP_PROTO(struct request_queue *q, struct bio *bio,
> @@ -337,6 +480,16 @@ TRACE_EVENT(block_split,
>  		  __entry->comm)
>  );
>  
> +/**
> + * block_remap - map request for a partition to the raw device
> + * @q: queue holding the operation
> + * @bio: revised operation
> + * @dev: device for the operation
> + * @from: original sector for the operation
> + *
> + * An operation for a partion on a block device has been mapped to the

                         partition

> + * raw block device.
> + */
>  TRACE_EVENT(block_remap,
>  
>  	TP_PROTO(struct request_queue *q, struct bio *bio, dev_t dev,
> @@ -370,6 +523,17 @@ TRACE_EVENT(block_remap,
>  		  (unsigned long long)__entry->old_sector)
>  );
>  
> +/**
> + * block_rq_remap - map request for a block operation request
> + * @q: queue holding the operation
> + * @rq: block IO operation request
> + * @dev: device for the operation
> + * @from: original sector for the operation
> + *
> + * The block operation request @rq in @q has been remapped.  The block
> + * operation request @rq holds the current information and @from hold
> + * the original sector.
> + */
>  TRACE_EVENT(block_rq_remap,
>  
>  	TP_PROTO(struct request_queue *q, struct request *rq, dev_t dev,


Thanks,
~Randy
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