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  1. 01 4月, 2010 7 次提交
    • S
      ring-buffer: Add lost event count to end of sub buffer · ff0ff84a
      由 Steven Rostedt 提交于 
      Currently, binary readers of the ring buffer only know where events were
lost, but not how many events were lost at that location.
This information is available, but it would require adding another
field to the sub buffer header to include it.

But when a event can not fit at the end of a sub buffer, it is written
to the next sub buffer. This means there is a good chance that the
buffer may have room to hold this counter. If it does, write
the counter at the end of the sub buffer and set another flag
in the data size field that states that this information exists.
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>
      ff0ff84a
    • S
      tracing: Show the lost events in the trace_pipe output · bc21b478
      由 Steven Rostedt 提交于 
      Now that the ring buffer can keep track of where events are lost.
Use this information to the output of trace_pipe:

       hackbench-3588  [001]  1326.701660: lock_acquire: ffffffff816591e0 read rcu_read_lock
       hackbench-3588  [001]  1326.701661: lock_acquire: ffff88003f4091f0 &(&dentry->d_lock)->rlock
       hackbench-3588  [001]  1326.701664: lock_release: ffff88003f4091f0 &(&dentry->d_lock)->rlock
CPU:1 [LOST 673 EVENTS]
       hackbench-3588  [001]  1326.702711: kmem_cache_free: call_site=ffffffff81102b85 ptr=ffff880026d96738
       hackbench-3588  [001]  1326.702712: lock_release: ffff88003e1480a8 &mm->mmap_sem
       hackbench-3588  [001]  1326.702713: lock_acquire: ffff88003e1480a8 &mm->mmap_sem

Even works with the function graph tracer:

 2) ! 170.098 us  |                                            }
 2)   4.036 us    |                                            rcu_irq_exit();
 2)   3.657 us    |                                            idle_cpu();
 2) ! 190.301 us  |                                          }
CPU:2 [LOST 2196 EVENTS]
 2)   0.853 us    |                            } /* cancel_dirty_page */
 2)               |                            remove_from_page_cache() {
 2)   1.578 us    |                              _raw_spin_lock_irq();
 2)               |                              __remove_from_page_cache() {

Note, it does not work with the iterator "trace" file, since it requires
the use of consuming the page from the ring buffer to determine how many
events were lost, which the iterator does not do.
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>
      bc21b478
    • S
      ring-buffer: Add place holder recording of dropped events · 66a8cb95
      由 Steven Rostedt 提交于 
      Currently, when the ring buffer drops events, it does not record
the fact that it did so. It does inform the writer that the event
was dropped by returning a NULL event, but it does not put in any
place holder where the event was dropped.

This is not a trivial thing to add because the ring buffer mostly
runs in overwrite (flight recorder) mode. That is, when the ring
buffer is full, new data will overwrite old data.

In a produce/consumer mode, where new data is simply dropped when
the ring buffer is full, it is trivial to add the placeholder
for dropped events. When there's more room to write new data, then
a special event can be added to notify the reader about the dropped
events.

But in overwrite mode, any new write can overwrite events. A place
holder can not be inserted into the ring buffer since there never
may be room. A reader could also come in at anytime and miss the
placeholder.

Luckily, the way the ring buffer works, the read side can find out
if events were lost or not, and how many events. Everytime a write
takes place, if it overwrites the header page (the next read) it
updates a "overrun" variable that keeps track of the number of
lost events. When a reader swaps out a page from the ring buffer,
it can record this number, perfom the swap, and then check to
see if the number changed, and take the diff if it has, which would be
the number of events dropped. This can be stored by the reader
and returned to callers of the reader.

Since the reader page swap will fail if the writer moved the head
page since the time the reader page set up the swap, this gives room
to record the overruns without worrying about races. If the reader
sets up the pages, records the overrun, than performs the swap,
if the swap succeeds, then the overrun variable has not been
updated since the setup before the swap.

For binary readers of the ring buffer, a flag is set in the header
of each sub page (sub buffer) of the ring buffer. This flag is embedded
in the size field of the data on the sub buffer, in the 31st bit (the size
can be 32 or 64 bits depending on the architecture), but only 27
bits needs to be used for the actual size (less actually).

We could add a new field in the sub buffer header to also record the
number of events dropped since the last read, but this will change the
format of the binary ring buffer a bit too much. Perhaps this change can
be made if the information on the number of events dropped is considered
important enough.

Note, the notification of dropped events is only used by consuming reads
or peeking at the ring buffer. Iterating over the ring buffer does not
keep this information because the necessary data is only available when
a page swap is made, and the iterator does not swap out pages.

Cc: Robert Richter <robert.richter@amd.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Li Zefan <lizf@cn.fujitsu.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: "Luis Claudio R. Goncalves" <lclaudio@uudg.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>
      66a8cb95
    • S
      tracing: Fix compile error in module tracepoints when MODULE_UNLOAD not set · eb0c5377
      由 Steven Rostedt 提交于 
      If modules are configured in the build but unloading of modules is not,
then the refcnt is not defined. Place the get/put module tracepoints
under CONFIG_MODULE_UNLOAD since it references this field in the module
structure.

As a side-effect, this patch also reduces the code when MODULE_UNLOAD
is not set, because these unused tracepoints are not created.
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>
      eb0c5377
    • L
      tracing: Remove side effect from module tracepoints that caused a GPF · ae832d1e
      由 Li Zefan 提交于 
      Remove the @refcnt argument, because it has side-effects, and arguments with
side-effects are not skipped by the jump over disabled instrumentation and are
executed even when the tracepoint is disabled.

This was also causing a GPF as found by Randy Dunlap:

Subject: 2.6.33 GP fault only when built with tracing
LKML-Reference: <4BA2B69D.3000309@oracle.com>

Note, the current 2.6.34-rc has a fix for the actual cause of the GPF,
but this fixes one of its triggers.
Tested-by: NRandy Dunlap <randy.dunlap@oracle.com>
Acked-by: NMathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: NLi Zefan <lizf@cn.fujitsu.com>
LKML-Reference: <4BA97FA7.6040406@cn.fujitsu.com>
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>
      ae832d1e
    • L
      tracing: Update comments · 50354a8a
      由 Li Zefan 提交于 
      Make some comments consistent with the code.
Signed-off-by: NLi Zefan <lizf@cn.fujitsu.com>
LKML-Reference: <4BA97FD0.7090202@cn.fujitsu.com>
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>
      50354a8a
    • L
      tracing: Convert some signal events to DEFINE_TRACE · 4bdde044
      由 Li Zefan 提交于 
      Use DECLARE_EVENT_CLASS to remove duplicate code:

text    data     bss     dec     hex filename
  23639    6084       8   29731    7423 kernel/signal.o.orig
  22727    6084       8   28819    7093 kernel/signal.o

2 events are converted:

  signal_queue_overflow: signal_overflow_fail, signal_lose_info

No functional change.
Acked-by: NMasami Hiramatsu <mhiramat@redhat.com>
Signed-off-by: NLi Zefan <lizf@cn.fujitsu.com>
LKML-Reference: <4BA97FBD.8070703@cn.fujitsu.com>
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>
      4bdde044
  3. 31 3月, 2010 2 次提交
  5. 30 3月, 2010 29 次提交
  7. 29 3月, 2010 2 次提交