Re: [RFC][PATCH 1/2] tracing: Add help of snapshot feature when snapshot is empty

[Hiraku Toyooka]

(03/06/2013 10:49 PM), Steven Rostedt wrote:
> From: "Steven Rostedt (Red Hat)"
> 
> When cat'ing the snapshot file, instead of showing an empty trace
> header like the trace file does, show how to use the snapshot
> feature.
> 
> Also, this is a good place to show if the snapshot has been allocated
> or not. Users may want to "pre allocate" the snapshot to have a fast
> "swap" of the current buffer. Otherwise, a swap would be slow and might
> fail as it would need to allocate the snapshot buffer, and that might
> fail under tight memory constraints.
> 
> Here's what it looked like before:
> 
>   # tracer: nop
>   #
>   # entries-in-buffer/entries-written: 0/0   #P:4
>   #
>   #  _-=> irqs-off
>   # / _=> need-resched
>   #| / _---=> hardirq/softirq
>   #|| / _--=> preempt-depth
>   #||| / delay
>   #   TASK-PID   CPU#  TIMESTAMP  FUNCTION
>   #  | |   |      | |
> 
> Here's what it looks like now:
> 
>   # tracer: nop
>   #
>   #
>   # * Snapshot is freed *
>   #
>   # Snapshot commands:
>   # echo 0 > snapshot : Clears and frees snapshot buffer
>   # echo 1 > snapshot : Allocates snapshot buffer, if not already allocated.
>   #  Takes a snapshot of the main buffer.
>   # echo 2 > snapshot : Clears snapshot buffer (but does not allocate)
>   #  (Doesn't have to be '2' works with any number that
>   #   is not a '0' or '1')
> 
> Cc: Hiraku Toyooka
> Signed-off-by: Steven Rostedt
> ---

Acked-by: Hiraku Toyooka 

>   kernel/trace/trace.c |   25 -
>   1 file changed, 24 insertions(+), 1 deletion(-)
> 
> diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
> index c2e2c23..9e3120b 100644
> --- a/kernel/trace/trace.c
> +++ b/kernel/trace/trace.c
> @@ -2400,6 +2400,27 @@ static void test_ftrace_alive(struct seq_file *m)
>   seq_printf(m, "#  MAY BE MISSING FUNCTION EVENTS\n");
>   }
>   
> +#ifdef CONFIG_TRACER_MAX_TRACE
> +static void print_snapshot_help(struct seq_file *m, struct trace_iterator 
> *iter)
> +{
> + if (iter->trace->allocated_snapshot)
> + seq_printf(m, "#\n# * Snapshot is allocated *\n#\n");
> + else
> + seq_printf(m, "#\n# * Snapshot is freed *\n#\n");
> +
> + seq_printf(m, "# Snapshot commands:\n");
> + seq_printf(m, "# echo 0 > snapshot : Clears and frees snapshot 
> buffer\n");
> + seq_printf(m, "# echo 1 > snapshot : Allocates snapshot buffer, if not 
> already allocated.\n");
> + seq_printf(m, "#  Takes a snapshot of the main 
> buffer.\n");
> + seq_printf(m, "# echo 2 > snapshot : Clears snapshot buffer (but does 
> not allocate)\n");
> + seq_printf(m, "#  (Doesn't have to be '2' works 
> with any number that\n");
> + seq_printf(m, "#   is not a '0' or '1')\n");
> +}
> +#else
> +/* Should never be called */
> +static inline void print_snapshot_help(struct seq_file *m, struct 
> trace_iterator *iter) { }
> +#endif
> +
>   static int s_show(struct seq_file *m, void *v)
>   {
>   struct trace_iterator *iter = v;
> @@ -2411,7 +2432,9 @@ static int s_show(struct seq_file *m, void *v)
>   seq_puts(m, "#\n");
>   test_ftrace_alive(m);
>   }
> - if (iter->trace && iter->trace->print_header)
> + if (iter->snapshot && trace_empty(iter))
> + print_snapshot_help(m, iter);
> + else if (iter->trace && iter->trace->print_header)
>   iter->trace->print_header(m);
>   else
>   trace_default_header(m);
> -- 1.7.10.4 .
> 

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[RFC][PATCH 1/2] tracing: Add help of snapshot feature when snapshot is empty

[Steven Rostedt]

From: "Steven Rostedt (Red Hat)" 

When cat'ing the snapshot file, instead of showing an empty trace
header like the trace file does, show how to use the snapshot
feature.

Also, this is a good place to show if the snapshot has been allocated
or not. Users may want to "pre allocate" the snapshot to have a fast
"swap" of the current buffer. Otherwise, a swap would be slow and might
fail as it would need to allocate the snapshot buffer, and that might
fail under tight memory constraints.

Here's what it looked like before:

 # tracer: nop
 #
 # entries-in-buffer/entries-written: 0/0   #P:4
 #
 #  _-=> irqs-off
 # / _=> need-resched
 #| / _---=> hardirq/softirq
 #|| / _--=> preempt-depth
 #||| / delay
 #   TASK-PID   CPU#  TIMESTAMP  FUNCTION
 #  | |   |      | |

Here's what it looks like now:

 # tracer: nop
 #
 #
 # * Snapshot is freed *
 #
 # Snapshot commands:
 # echo 0 > snapshot : Clears and frees snapshot buffer
 # echo 1 > snapshot : Allocates snapshot buffer, if not already allocated.
 #  Takes a snapshot of the main buffer.
 # echo 2 > snapshot : Clears snapshot buffer (but does not allocate)
 #  (Doesn't have to be '2' works with any number that
 #   is not a '0' or '1')

Cc: Hiraku Toyooka 
Signed-off-by: Steven Rostedt 
---
 kernel/trace/trace.c |   25 -
 1 file changed, 24 insertions(+), 1 deletion(-)

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index c2e2c23..9e3120b 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -2400,6 +2400,27 @@ static void test_ftrace_alive(struct seq_file *m)
seq_printf(m, "#  MAY BE MISSING FUNCTION EVENTS\n");
 }
 
+#ifdef CONFIG_TRACER_MAX_TRACE
+static void print_snapshot_help(struct seq_file *m, struct trace_iterator 
*iter)
+{
+   if (iter->trace->allocated_snapshot)
+   seq_printf(m, "#\n# * Snapshot is allocated *\n#\n");
+   else
+   seq_printf(m, "#\n# * Snapshot is freed *\n#\n");
+
+   seq_printf(m, "# Snapshot commands:\n");
+   seq_printf(m, "# echo 0 > snapshot : Clears and frees snapshot 
buffer\n");
+   seq_printf(m, "# echo 1 > snapshot : Allocates snapshot buffer, if not 
already allocated.\n");
+   seq_printf(m, "#  Takes a snapshot of the main 
buffer.\n");
+   seq_printf(m, "# echo 2 > snapshot : Clears snapshot buffer (but does 
not allocate)\n");
+   seq_printf(m, "#  (Doesn't have to be '2' works 
with any number that\n");
+   seq_printf(m, "#   is not a '0' or '1')\n");
+}
+#else
+/* Should never be called */
+static inline void print_snapshot_help(struct seq_file *m, struct 
trace_iterator *iter) { }
+#endif
+
 static int s_show(struct seq_file *m, void *v)
 {
struct trace_iterator *iter = v;
@@ -2411,7 +2432,9 @@ static int s_show(struct seq_file *m, void *v)
seq_puts(m, "#\n");
test_ftrace_alive(m);
}
-   if (iter->trace && iter->trace->print_header)
+   if (iter->snapshot && trace_empty(iter))
+   print_snapshot_help(m, iter);
+   else if (iter->trace && iter->trace->print_header)
iter->trace->print_header(m);
else
trace_default_header(m);
-- 
1.7.10.4


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[RFC][PATCH 1/2] tracing: Add help of snapshot feature when snapshot is empty

[Steven Rostedt]

From: Steven Rostedt (Red Hat) srost...@redhat.com

When cat'ing the snapshot file, instead of showing an empty trace
header like the trace file does, show how to use the snapshot
feature.

Also, this is a good place to show if the snapshot has been allocated
or not. Users may want to pre allocate the snapshot to have a fast
swap of the current buffer. Otherwise, a swap would be slow and might
fail as it would need to allocate the snapshot buffer, and that might
fail under tight memory constraints.

Here's what it looked like before:

 # tracer: nop
 #
 # entries-in-buffer/entries-written: 0/0   #P:4
 #
 #  _-= irqs-off
 # / _= need-resched
 #| / _---= hardirq/softirq
 #|| / _--= preempt-depth
 #||| / delay
 #   TASK-PID   CPU#  TIMESTAMP  FUNCTION
 #  | |   |      | |

Here's what it looks like now:

 # tracer: nop
 #
 #
 # * Snapshot is freed *
 #
 # Snapshot commands:
 # echo 0  snapshot : Clears and frees snapshot buffer
 # echo 1  snapshot : Allocates snapshot buffer, if not already allocated.
 #  Takes a snapshot of the main buffer.
 # echo 2  snapshot : Clears snapshot buffer (but does not allocate)
 #  (Doesn't have to be '2' works with any number that
 #   is not a '0' or '1')

Cc: Hiraku Toyooka hiraku.toyooka...@hitachi.com
Signed-off-by: Steven Rostedt rost...@goodmis.org
---
 kernel/trace/trace.c |   25 -
 1 file changed, 24 insertions(+), 1 deletion(-)

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index c2e2c23..9e3120b 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -2400,6 +2400,27 @@ static void test_ftrace_alive(struct seq_file *m)
seq_printf(m, #  MAY BE MISSING FUNCTION EVENTS\n);
 }
 
+#ifdef CONFIG_TRACER_MAX_TRACE
+static void print_snapshot_help(struct seq_file *m, struct trace_iterator 
*iter)
+{
+   if (iter-trace-allocated_snapshot)
+   seq_printf(m, #\n# * Snapshot is allocated *\n#\n);
+   else
+   seq_printf(m, #\n# * Snapshot is freed *\n#\n);
+
+   seq_printf(m, # Snapshot commands:\n);
+   seq_printf(m, # echo 0  snapshot : Clears and frees snapshot 
buffer\n);
+   seq_printf(m, # echo 1  snapshot : Allocates snapshot buffer, if not 
already allocated.\n);
+   seq_printf(m, #  Takes a snapshot of the main 
buffer.\n);
+   seq_printf(m, # echo 2  snapshot : Clears snapshot buffer (but does 
not allocate)\n);
+   seq_printf(m, #  (Doesn't have to be '2' works 
with any number that\n);
+   seq_printf(m, #   is not a '0' or '1')\n);
+}
+#else
+/* Should never be called */
+static inline void print_snapshot_help(struct seq_file *m, struct 
trace_iterator *iter) { }
+#endif
+
 static int s_show(struct seq_file *m, void *v)
 {
struct trace_iterator *iter = v;
@@ -2411,7 +2432,9 @@ static int s_show(struct seq_file *m, void *v)
seq_puts(m, #\n);
test_ftrace_alive(m);
}
-   if (iter-trace  iter-trace-print_header)
+   if (iter-snapshot  trace_empty(iter))
+   print_snapshot_help(m, iter);
+   else if (iter-trace  iter-trace-print_header)
iter-trace-print_header(m);
else
trace_default_header(m);
-- 
1.7.10.4


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Re: [RFC][PATCH 1/2] tracing: Add help of snapshot feature when snapshot is empty

[Hiraku Toyooka]

(03/06/2013 10:49 PM), Steven Rostedt wrote:
 From: Steven Rostedt (Red Hat)srost...@redhat.com
 
 When cat'ing the snapshot file, instead of showing an empty trace
 header like the trace file does, show how to use the snapshot
 feature.
 
 Also, this is a good place to show if the snapshot has been allocated
 or not. Users may want to pre allocate the snapshot to have a fast
 swap of the current buffer. Otherwise, a swap would be slow and might
 fail as it would need to allocate the snapshot buffer, and that might
 fail under tight memory constraints.
 
 Here's what it looked like before:
 
   # tracer: nop
   #
   # entries-in-buffer/entries-written: 0/0   #P:4
   #
   #  _-= irqs-off
   # / _= need-resched
   #| / _---= hardirq/softirq
   #|| / _--= preempt-depth
   #||| / delay
   #   TASK-PID   CPU#  TIMESTAMP  FUNCTION
   #  | |   |      | |
 
 Here's what it looks like now:
 
   # tracer: nop
   #
   #
   # * Snapshot is freed *
   #
   # Snapshot commands:
   # echo 0  snapshot : Clears and frees snapshot buffer
   # echo 1  snapshot : Allocates snapshot buffer, if not already allocated.
   #  Takes a snapshot of the main buffer.
   # echo 2  snapshot : Clears snapshot buffer (but does not allocate)
   #  (Doesn't have to be '2' works with any number that
   #   is not a '0' or '1')
 
 Cc: Hiraku Toyookahiraku.toyooka...@hitachi.com
 Signed-off-by: Steven Rostedtrost...@goodmis.org
 ---

Acked-by: Hiraku Toyooka hiraku.toyooka...@hitachi.com

   kernel/trace/trace.c |   25 -
   1 file changed, 24 insertions(+), 1 deletion(-)
 
 diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
 index c2e2c23..9e3120b 100644
 --- a/kernel/trace/trace.c
 +++ b/kernel/trace/trace.c
 @@ -2400,6 +2400,27 @@ static void test_ftrace_alive(struct seq_file *m)
   seq_printf(m, #  MAY BE MISSING FUNCTION EVENTS\n);
   }
   
 +#ifdef CONFIG_TRACER_MAX_TRACE
 +static void print_snapshot_help(struct seq_file *m, struct trace_iterator 
 *iter)
 +{
 + if (iter-trace-allocated_snapshot)
 + seq_printf(m, #\n# * Snapshot is allocated *\n#\n);
 + else
 + seq_printf(m, #\n# * Snapshot is freed *\n#\n);
 +
 + seq_printf(m, # Snapshot commands:\n);
 + seq_printf(m, # echo 0  snapshot : Clears and frees snapshot 
 buffer\n);
 + seq_printf(m, # echo 1  snapshot : Allocates snapshot buffer, if not 
 already allocated.\n);
 + seq_printf(m, #  Takes a snapshot of the main 
 buffer.\n);
 + seq_printf(m, # echo 2  snapshot : Clears snapshot buffer (but does 
 not allocate)\n);
 + seq_printf(m, #  (Doesn't have to be '2' works 
 with any number that\n);
 + seq_printf(m, #   is not a '0' or '1')\n);
 +}
 +#else
 +/* Should never be called */
 +static inline void print_snapshot_help(struct seq_file *m, struct 
 trace_iterator *iter) { }
 +#endif
 +
   static int s_show(struct seq_file *m, void *v)
   {
   struct trace_iterator *iter = v;
 @@ -2411,7 +2432,9 @@ static int s_show(struct seq_file *m, void *v)
   seq_puts(m, #\n);
   test_ftrace_alive(m);
   }
 - if (iter-trace  iter-trace-print_header)
 + if (iter-snapshot  trace_empty(iter))
 + print_snapshot_help(m, iter);
 + else if (iter-trace  iter-trace-print_header)
   iter-trace-print_header(m);
   else
   trace_default_header(m);
 -- 1.7.10.4 .
 

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