The names used to display the field and type in the event format
files are copied, as well as the system name that is displayed.
All these names are created by constant values passed in.
If one of theses values were to be removed by a module, the module
would also be required to remove any event it created.
By using the strings directly, we can save over 100K of memory.
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
The event structures used by the trace events are mostly persistent,
but they are also allocated by kmalloc, which is not the best at
allocating space for what is used. By converting these kmallocs
into kmem_cache_allocs, we can save over 50K of space that is
permanently allocated.
After boot we have:
slab name active allocated size
--------- ------ --------- ----
ftrace_event_file 979 1005 56 67 1
ftrace_event_field 2301 2310 48 77 1
The ftrace_event_file has at boot up 979 active objects out of
1005 allocated in the slabs. Each object is 56 bytes. In a normal
kmalloc, that would allocate 64 bytes for each object.
1005 - 979 = 26 objects not used
26 * 56 = 1456 bytes wasted
But if we used kmalloc:
64 - 56 = 8 bytes unused per allocation
8 * 979 = 7832 bytes wasted
7832 - 1456 = 6376 bytes in savings
Doing the same for ftrace_event_field where there's 2301 objects
allocated in a slab that can hold 2310 with 48 bytes each we have:
2310 - 2301 = 9 objects not used
9 * 48 = 432 bytes wasted
A kmalloc would also use 64 bytes per object:
64 - 48 = 16 bytes unused per allocation
16 * 2301 = 36816 bytes wasted!
36816 - 432 = 36384 bytes in savings
This change gives us a total of 42760 bytes in savings. At least
on my machine, but as there's a lot of these persistent objects
for all configurations that use trace points, this is a net win.
Thanks to Ezequiel Garcia for his trace_analyze presentation which
pointed out the wasted space in my code.
Cc: Ezequiel Garcia <elezegarcia@gmail.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
With the new descriptors used to allow multiple buffers in the
tracing directory added, the kernel command line parameter
trace_events=... no longer works. This is because the top level
(global) trace array now has a list of descriptors associated
with the events and the files in the debugfs directory. But in
early bootup, when the command line is processed and the events
enabled, the trace array list of events has not been set up yet.
Without the list of events in the trace array, the setting of
events to record will fail because it would not match any events.
The solution is to set up the top level array in two stages.
The first is to just add the ftrace file descriptors that just point
to the events. This will allow events to be enabled and start tracing.
The second stage is called after the filesystem is set up, and this
stage will create the debugfs event files and directories associated
with the trace array events.
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Add a method to the hijacked dentry descriptor of the
"instances" directory to allow for rmdir to remove an
instance of a multibuffer.
Example:
cd /debug/tracing/instances
mkdir hello
ls
hello/
rmdir hello
ls
Like the mkdir method, the i_mutex is dropped for the instances
directory. The instances directory is created at boot up and can
not be renamed or removed. The trace_types_lock mutex is used to
synchronize adding and removing of instances.
I've run several stress tests with different threads trying to
create and delete directories of the same name, and it has stood
up fine.
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Add the interface ("instances" directory) to add multiple buffers
to ftrace. To create a new instance, simply do a mkdir in the
instances directory:
This will create a directory with the following:
# cd instances
# mkdir foo
# ls foo
buffer_size_kb free_buffer trace_clock trace_pipe
buffer_total_size_kb set_event trace_marker tracing_enabled
events/ trace trace_options tracing_on
Currently only events are able to be set, and there isn't a way
to delete a buffer when one is created (yet).
Note, the i_mutex lock is dropped from the parent "instances"
directory during the mkdir operation. As the "instances" directory
can not be renamed or deleted (created on boot), I do not see
any harm in dropping the lock. The creation of the sub directories
is protected by trace_types_lock mutex, which only lets one
instance get into the code path at a time. If two tasks try to
create or delete directories of the same name, only one will occur
and the other will fail with -EEXIST.
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
The trace events for ftrace are all defined via global variables.
The arrays of events and event systems are linked to a global list.
This prevents multiple users of the event system (what to enable and
what not to).
By adding descriptors to represent the event/file relation, as well
as to which trace_array descriptor they are associated with, allows
for more than one set of events to be defined. Once the trace events
files have a link between the trace event and the trace_array they
are associated with, we can create multiple trace_arrays that can
record separate events in separate buffers.
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Due to a userspace issue with PowerTop v2beta, which hardcoded
the offset of event fields that it was using, it broke when
we removed the Big Kernel Lock counter from the event header.
(commit e6e1e2593 "tracing: Remove lock_depth from event entry")
Because this broke userspace, it was determined that we must
keep those 4 bytes around.
(commit a3a4a5acd "Regression: partial revert "tracing: Remove lock_depth from event entry"")
This unfortunately wastes space in the ring buffer. 4 bytes per
event, where a lot of events are just 24 bytes. That's 16% of the
buffer wasted. A million events will add 4 megs of white space
into the buffer.
It was later noticed that PowerTop v2beta could not work on systems
where the kernel was 64 bit but the userspace was 32 bits.
The reason was because the offsets are different between the
two and the hard coded offset of one would not work with the other.
With PowerTop v2 final, it implemented the same interface that both
perf and trace-cmd use. That is, it reads the format file of
the event to find the offsets of the fields it needs. This fixes
the problem with running powertop on a 32 bit userspace running
on a 64 bit kernel. It also no longer requires the 4 byte padding.
As PowerTop v2 has been out for a while, and is included in all
major distributions, it is time that we can safely remove the
4 bytes of padding. Users of PowerTop v2beta should upgrade to
PowerTop v2 final.
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Acked-by: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Have the ring buffer commit function use the irq_work infrastructure to
wake up any waiters waiting on the ring buffer for new data. The irq_work
was created for such a purpose, where doing the actual wake up at the
time of adding data is too dangerous, as an event or function trace may
be in the midst of the work queue locks and cause deadlocks. The irq_work
will either delay the action to the next timer interrupt, or trigger an IPI
to itself forcing an interrupt to do the work (in a safe location).
With irq_work, all ring buffer commits can safely do wakeups, removing
the need for the ring buffer commit "nowake" variants, which were used
by events and function tracing. All commits can now safely use the
normal commit, and the "nowake" variants can be removed.
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
The open function used by available_events is the same as set_event even
though it uses different seq functions. This causes a side effect of
writing into available_events clearing all events, even though
available_events is suppose to be read only.
There's no reason to keep a single function for just the open and have
both use different functions for everything else. It is a little
confusing and causes strange behavior. Just have each have their own
function.
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
If comm recording is not enabled when trace_printk() is used then
you just get this type of output:
[ adding trace_printk("hello! %d", irq); in do_IRQ ]
<...>-2843 [001] d.h. 80.812300: do_IRQ: hello! 14
<...>-2734 [002] d.h2 80.824664: do_IRQ: hello! 14
<...>-2713 [003] d.h. 80.829971: do_IRQ: hello! 14
<...>-2814 [000] d.h. 80.833026: do_IRQ: hello! 14
By enabling the comm recorder when trace_printk is enabled:
hackbench-6715 [001] d.h. 193.233776: do_IRQ: hello! 21
sshd-2659 [001] d.h. 193.665862: do_IRQ: hello! 21
<idle>-0 [001] d.h1 193.665996: do_IRQ: hello! 21
Suggested-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
This patch splits trace event initialization in two stages:
* ftrace enable
* sysfs event entry creation
This allows to capture trace events from an earlier point
by using 'trace_event' kernel parameter and is important
to trace boot-up allocations.
Note that, in order to enable events at core_initcall,
it's necessary to move init_ftrace_syscalls() from
core_initcall to early_initcall.
Link: http://lkml.kernel.org/r/1347461277-25302-1-git-send-email-elezegarcia@gmail.com
Signed-off-by: Ezequiel Garcia <elezegarcia@gmail.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
As more users of the function tracer utility are being added, they do
not always add the necessary recursion protection. To protect from
function recursion due to tracing, if the callback ftrace_ops does not
specifically specify that it protects against recursion (by setting
the FTRACE_OPS_FL_RECURSION_SAFE flag), the list operation will be
called by the mcount trampoline which adds recursion protection.
If the flag is set, then the function will be called directly with no
extra protection.
Note, the list operation is called if more than one function callback
is registered, or if the arch does not support all of the function
tracer features.
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Return as the 4th paramater to the function tracer callback the pt_regs.
Later patches that implement regs passing for the architectures will require
having the ftrace_ops set the SAVE_REGS flag, which will tell the arch
to take the time to pass a full set of pt_regs to the ftrace_ops callback
function. If the arch does not support it then it should pass NULL.
If an arch can pass full regs, then it should define:
ARCH_SUPPORTS_FTRACE_SAVE_REGS to 1
Link: http://lkml.kernel.org/r/20120702201821.019966811@goodmis.org
Reviewed-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Currently the function trace callback receives only the ip and parent_ip
of the function that it traced. It would be more powerful to also return
the ops that registered the function as well. This allows the same function
to act differently depending on what ftrace_ops registered it.
Link: http://lkml.kernel.org/r/20120612225424.267254552@goodmis.org
Reviewed-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
With the adding of function tracing event to perf, it caused a
side effect that produces the following warning when enabling all
events in ftrace:
# echo 1 > /sys/kernel/debug/tracing/events/enable
[console]
event trace: Could not enable event function
This is because when enabling all events via the debugfs system
it ignores events that do not have a ->reg() function assigned.
This was to skip over the ftrace internal events (as they are
not TRACE_EVENTs). But as the ftrace function event now has
a ->reg() function attached to it for use with perf, it is no
longer ignored.
Worse yet, this ->reg() function is being called when it should
not be. It returns an error and causes the above warning to
be printed.
By adding a new event_call flag (TRACE_EVENT_FL_IGNORE_ENABLE)
and have all ftrace internel event structures have it set,
setting the events/enable will no longe try to incorrectly enable
the function event and does not warn.
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Adding TRACE_REG_PERF_OPEN and TRACE_REG_PERF_CLOSE to differentiate
register/unregister from open/close actions.
The register/unregister actions are invoked for the first/last
tracepoint user when opening/closing the event.
The open/close actions are invoked for each tracepoint user when
opening/closing the event.
Link: http://lkml.kernel.org/r/1329317514-8131-3-git-send-email-jolsa@redhat.com
Acked-by: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Jiri Olsa <jolsa@redhat.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Fix a bug introduced by e9dbfae5, which prevents event_subsystem from
ever being released.
Ref_count was added to keep track of subsystem users, not for counting
events. Subsystem is created with ref_count = 1, so there is no need to
increment it for every event, we have nr_events for that. Fix this by
touching ref_count only when we actually have a new user -
subsystem_open().
Cc: stable@vger.kernel.org
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
Link: http://lkml.kernel.org/r/1320052062-7846-1-git-send-email-idryomov@gmail.com
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
The "enable" file for the event system can be removed when a module
is unloaded and the event system only has events from that module.
As the event system nr_events count goes to zero, it may be freed
if its ref_count is also set to zero.
Like the "filter" file, the "enable" file may be opened by a task and
referenced later, after a module has been unloaded and the events for
that event system have been removed.
Although the "filter" file referenced the event system structure,
the "enable" file only references a pointer to the event system
name. Since the name is freed when the event system is removed,
it is possible that an access to the "enable" file may reference
a freed pointer.
Update the "enable" file to use the subsystem_open() routine that
the "filter" file uses, to keep a reference to the event system
structure while the "enable" file is opened.
Cc: <stable@kernel.org>
Reported-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
The event system is freed when its nr_events is set to zero. This happens
when a module created an event system and then later the module is
removed. Modules may share systems, so the system is allocated when
it is created and freed when the modules are unloaded and all the
events under the system are removed (nr_events set to zero).
The problem arises when a task opened the "filter" file for the
system. If the module is unloaded and it removed the last event for
that system, the system structure is freed. If the task that opened
the filter file accesses the "filter" file after the system has
been freed, the system will access an invalid pointer.
By adding a ref_count, and using it to keep track of what
is using the event system, we can free it after all users
are finished with the event system.
Cc: <stable@kernel.org>
Reported-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
The self tests for event tracer does not check if the function
tracing was successfully activated. It needs to before it continues
the tests, otherwise the wrong errors may be reported.
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
This partially reverts commit e6e1e25935.
That commit changed the structure layout of the trace structure, which
in turn broke PowerTOP (1.9x generation) quite badly.
I appreciate not wanting to expose the variable in question, and
PowerTOP was not using it, so I've replaced the variable with just a
padding field - that way if in the future a new field is needed it can
just use this padding field.
Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Steven Rostedt
Ezequiel Garcia
Yuanhan Liu
Jiri Olsa
Ilya Dryomov
Ingo Molnar
Peter Huewe
Arjan van de Ven