Date:	Mon, 21 Dec 2009 20:36:10 +0000
From:	Mel Gorman <mel@....ul.ie>
To:	Randy Dunlap <randy.dunlap@...cle.com>
Cc:	lkml <linux-kernel@...r.kernel.org>,
	akpm <akpm@...ux-foundation.org>
Subject: Re: [PATCH 2/4] Documentation: update tracepoint-analysis.txt

On Fri, Dec 18, 2009 at 03:17:04PM -0800, Randy Dunlap wrote:
> From: Randy Dunlap <randy.dunlap@...cle.com>
> 
> Fix grammar, spelling, punctuation, hyphenation, section numbering.
> Tell what PCL means.
> 

Thanks.

> Signed-off-by: Randy Dunlap <randy.dunlap@...cle.com>
> Cc: Mel Gorman <mel@....ul.ie>

Acked-by: Mel Gorman <mel@....ul.ie>

> ---
>  Documentation/trace/tracepoint-analysis.txt |   60 ++++++++++++++--------------
>  1 file changed, 30 insertions(+), 30 deletions(-)
> 
> --- lnx-2633-rc1.orig/Documentation/trace/tracepoint-analysis.txt
> +++ lnx-2633-rc1/Documentation/trace/tracepoint-analysis.txt
> @@ -10,8 +10,8 @@ Tracepoints (see Documentation/trace/tra
>  creating custom kernel modules to register probe functions using the event
>  tracing infrastructure.
>  
> -Simplistically, tracepoints will represent an important event that when can
> -be taken in conjunction with other tracepoints to build a "Big Picture" of
> +Simplistically, tracepoints represent important events that can be
> +taken in conjunction with other tracepoints to build a "Big Picture" of
>  what is going on within the system. There are a large number of methods for
>  gathering and interpreting these events. Lacking any current Best Practises,
>  this document describes some of the methods that can be used.
> @@ -33,12 +33,12 @@ calling
>  
>  will give a fair indication of the number of events available.
>  
> -2.2 PCL
> +2.2 PCL (Performance Counters for Linux)
>  -------
>  
> -Discovery and enumeration of all counters and events, including tracepoints
> +Discovery and enumeration of all counters and events, including tracepoints,
>  are available with the perf tool. Getting a list of available events is a
> -simple case of
> +simple case of:
>  
>    $ perf list 2>&1 | grep Tracepoint
>    ext4:ext4_free_inode                     [Tracepoint event]
> @@ -49,19 +49,19 @@ simple case of
>    [ .... remaining output snipped .... ]
>  
>  
> -2. Enabling Events
> +3. Enabling Events
>  ==================
>  
> -2.1 System-Wide Event Enabling
> +3.1 System-Wide Event Enabling
>  ------------------------------
>  
>  See Documentation/trace/events.txt for a proper description on how events
>  can be enabled system-wide. A short example of enabling all events related
> -to page allocation would look something like
> +to page allocation would look something like:
>  
>    $ for i in `find /sys/kernel/debug/tracing/events -name "enable" | grep mm_`; do echo 1 > $i; done
>  
> -2.2 System-Wide Event Enabling with SystemTap
> +3.2 System-Wide Event Enabling with SystemTap
>  ---------------------------------------------
>  
>  In SystemTap, tracepoints are accessible using the kernel.trace() function
> @@ -86,7 +86,7 @@ were allocating the pages.
>            print_count()
>    }
>  
> -2.3 System-Wide Event Enabling with PCL
> +3.3 System-Wide Event Enabling with PCL
>  ---------------------------------------
>  
>  By specifying the -a switch and analysing sleep, the system-wide events
> @@ -107,16 +107,16 @@ for a duration of time can be examined.
>  Similarly, one could execute a shell and exit it as desired to get a report
>  at that point.
>  
> -2.4 Local Event Enabling
> +3.4 Local Event Enabling
>  ------------------------
>  
>  Documentation/trace/ftrace.txt describes how to enable events on a per-thread
>  basis using set_ftrace_pid.
>  
> -2.5 Local Event Enablement with PCL
> +3.5 Local Event Enablement with PCL
>  -----------------------------------
>  
> -Events can be activate and tracked for the duration of a process on a local
> +Events can be activated and tracked for the duration of a process on a local
>  basis using PCL such as follows.
>  
>    $ perf stat -e kmem:mm_page_alloc -e kmem:mm_page_free_direct \
> @@ -131,18 +131,18 @@ basis using PCL such as follows.
>  
>      0.973913387  seconds time elapsed
>  
> -3. Event Filtering
> +4. Event Filtering
>  ==================
>  
>  Documentation/trace/ftrace.txt covers in-depth how to filter events in
>  ftrace.  Obviously using grep and awk of trace_pipe is an option as well
>  as any script reading trace_pipe.
>  
> -4. Analysing Event Variances with PCL
> +5. Analysing Event Variances with PCL
>  =====================================
>  
>  Any workload can exhibit variances between runs and it can be important
> -to know what the standard deviation in. By and large, this is left to the
> +to know what the standard deviation is. By and large, this is left to the
>  performance analyst to do it by hand. In the event that the discrete event
>  occurrences are useful to the performance analyst, then perf can be used.
>  
> @@ -166,7 +166,7 @@ In the event that some higher-level even
>  aggregation of discrete events, then a script would need to be developed.
>  
>  Using --repeat, it is also possible to view how events are fluctuating over
> -time on a system wide basis using -a and sleep.
> +time on a system-wide basis using -a and sleep.
>  
>    $ perf stat -e kmem:mm_page_alloc -e kmem:mm_page_free_direct \
>  		-e kmem:mm_pagevec_free \
> @@ -180,7 +180,7 @@ time on a system wide basis using -a and
>  
>      1.002251757  seconds time elapsed   ( +-   0.005% )
>  
> -5. Higher-Level Analysis with Helper Scripts
> +6. Higher-Level Analysis with Helper Scripts
>  ============================================
>  
>  When events are enabled the events that are triggering can be read from
> @@ -190,11 +190,11 @@ be gathered on-line as appropriate. Exam
>  
>    o Reading information from /proc for the PID that triggered the event
>    o Deriving a higher-level event from a series of lower-level events.
> -  o Calculate latencies between two events
> +  o Calculating latencies between two events
>  
>  Documentation/trace/postprocess/trace-pagealloc-postprocess.pl is an example
>  script that can read trace_pipe from STDIN or a copy of a trace. When used
> -on-line, it can be interrupted once to generate a report without existing
> +on-line, it can be interrupted once to generate a report without exiting
>  and twice to exit.
>  
>  Simplistically, the script just reads STDIN and counts up events but it
> @@ -212,12 +212,12 @@ also can do more such as
>      processes, the parent process responsible for creating all the helpers
>      can be identified
>  
> -6. Lower-Level Analysis with PCL
> +7. Lower-Level Analysis with PCL
>  ================================
>  
> -There may also be a requirement to identify what functions with a program
> +There may also be a requirement to identify what functions within a program
>  were generating events within the kernel. To begin this sort of analysis, the
> -data must be recorded. At the time of writing, this required root
> +data must be recorded. At the time of writing, this required root:
>  
>    $ perf record -c 1 \
>  	-e kmem:mm_page_alloc -e kmem:mm_page_free_direct \
> @@ -253,11 +253,11 @@ perf report.
>    # (For more details, try: perf report --sort comm,dso,symbol)
>    #
>  
> -According to this, the vast majority of events occured triggered on events
> -within the VDSO. With simple binaries, this will often be the case so lets
> +According to this, the vast majority of events triggered on events
> +within the VDSO. With simple binaries, this will often be the case so let's
>  take a slightly different example. In the course of writing this, it was
> -noticed that X was generating an insane amount of page allocations so lets look
> -at it
> +noticed that X was generating an insane amount of page allocations so let's look
> +at it:
>  
>    $ perf record -c 1 -f \
>  		-e kmem:mm_page_alloc -e kmem:mm_page_free_direct \
> @@ -280,8 +280,8 @@ This was interrupted after a few seconds
>    # (For more details, try: perf report --sort comm,dso,symbol)
>    #
>  
> -So, almost half of the events are occuring in a library. To get an idea which
> -symbol.
> +So, almost half of the events are occurring in a library. To get an idea which
> +symbol:
>  
>    $ perf report --sort comm,dso,symbol
>    # Samples: 27666
> @@ -297,7 +297,7 @@ symbol.
>         0.01%     Xorg  /opt/gfx-test/lib/libpixman-1.so.0.13.1  [.] get_fast_path
>         0.00%     Xorg  [kernel]                                 [k] ftrace_trace_userstack
>  
> -To see where within the function pixmanFillsse2 things are going wrong
> +To see where within the function pixmanFillsse2 things are going wrong:
>  
>    $ perf annotate pixmanFillsse2
>    [ ... ]
> 
> 

-- 
Mel Gorman
Part-time Phd Student                          Linux Technology Center
University of Limerick                         IBM Dublin Software Lab
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