user/sven/linux.git/include/linux/ftrace.h, branch v3.18.67

ftrace: Replace tramp_hash with old_*_hash to save space

2014-09-10T14:48:45Z

Allowing function callbacks to declare their own trampolines requires that each ftrace_ops that has a trampoline must have some sort of accounting that keeps track of which ops has a trampoline attached to a record. The easy way to solve this was to add a "tramp_hash" that created a hash entry for every function that a ops uses with a trampoline. But since we can have literally tens of thousands of functions being traced, that means we need tens of thousands of descriptors to map the ops to the function in the hash. This is quite expensive and can cause enabling and disabling the function graph tracer to take some time to start and stop. It can take up to several seconds to disable or enable all functions in the function graph tracer for this reason. The better approach albeit more complex, is to keep track of how ops are being enabled and disabled, and use that along with the counting of the number of ops attached to records, to determive what ops has a trampoline attached to a record at enabling and disabling of tracing. To do this, the tramp_hash has been replaced with an old_filter_hash and old_notrace_hash, which get the copy of the ops filter_hash and notrace_hash respectively. The old hashes is kept until the ops has been modified or removed and the old hashes are used with the logic of the accounting to determine the ops that have the trampoline of a record. The reason this has less of a footprint is due to the trick that an "empty" hash in the filter_hash means "all functions" and an empty hash in the notrace hash means "no functions" in the hash. This is much more efficienct, doesn't have the delay, and takes up much less memory, as we do not need to map all the functions but just figure out which functions are mapped at the time it is enabled or disabled. Signed-off-by: Steven Rostedt

ftrace: Annotate the ops operation on update

2014-09-10T14:48:44Z

Add three new flags for ftrace_ops: FTRACE_OPS_FL_ADDING FTRACE_OPS_FL_REMOVING FTRACE_OPS_FL_MODIFYING These will be set for the ftrace_ops when they are first added to the function tracing, being removed from function tracing or just having their functions changed from function tracing, respectively. This will be needed to remove the tramp_hash, which can grow quite big. The tramp_hash is used to note what functions a ftrace_ops is using a trampoline for. Denoting which ftrace_ops is being modified, will allow us to use the ftrace_ops hashes themselves, which are much smaller as they have a global flag to denote if a ftrace_ops is tracing all functions, as well as a notrace hash if the ftrace_ops is tracing all but a few. The tramp_hash just creates a hash item for every function, which can go into the 10s of thousands if all functions are using the ftrace_ops trampoline. Signed-off-by: Steven Rostedt

ftrace: Add helper function ftrace_ops_get_func()

2014-09-09T23:26:06Z

Add the helper function to what the mcount trampoline is to call for a ftrace_ops function. This helper will be used by arch code in the future to set up dynamic trampolines. But as this does the same tests that are performed in choosing what function to call for the default mcount trampoline, might as well use it to clean up the existing code. Signed-off-by: Steven Rostedt

ftrace: Allow ftrace_ops to use the hashes from other ops

2014-08-22T17:18:48Z

Currently the top level debug file system function tracer shares its ftrace_ops with the function graph tracer. This was thought to be fine because the tracers are not used together, as one can only enable function or function_graph tracer in the current_tracer file. But that assumption proved to be incorrect. The function profiler can use the function graph tracer when function tracing is enabled. Since all function graph users uses the function tracing ftrace_ops this causes a conflict and when a user enables both function profiling as well as the function tracer it will crash ftrace and disable it. The quick solution so far is to move them as separate ftrace_ops like it was earlier. The problem though is to synchronize the functions that are traced because both function and function_graph tracer are limited by the selections made in the set_ftrace_filter and set_ftrace_notrace files. To handle this, a new structure is made called ftrace_ops_hash. This structure will now hold the filter_hash and notrace_hash, and the ftrace_ops will point to this structure. That will allow two ftrace_ops to share the same hashes. Since most ftrace_ops do not share the hashes, and to keep allocation simple, the ftrace_ops structure will include both a pointer to the ftrace_ops_hash called func_hash, as well as the structure itself, called local_hash. When the ops are registered, the func_hash pointer will be initialized to point to the local_hash within the ftrace_ops structure. Some of the ftrace internal ftrace_ops will be initialized statically. This will allow for the function and function_graph tracer to have separate ops but still share the same hash tables that determine what functions they trace. Cc: stable@vger.kernel.org # 3.16 (apply after 3.17-rc4 is out) Signed-off-by: Steven Rostedt

ftrace: Rename ftrace_ops field from trampolines to nr_trampolines

2014-07-23T19:03:00Z

Having two fields within the same struct that is off by one character can be confusing and error prone. Rename the counter "trampolines" to "nr_trampolines" to explicitly show it is a counter and not to be confused by the "trampoline" field. Suggested-by: Oleg Nesterov Signed-off-by: Steven Rostedt

tracing: Remove function_trace_stop and HAVE_FUNCTION_TRACE_MCOUNT_TEST

2014-07-18T17:58:12Z

All users of function_trace_stop and HAVE_FUNCTION_TRACE_MCOUNT_TEST have been removed. We can safely remove them from the kernel. Reviewed-by: Masami Hiramatsu Signed-off-by: Steven Rostedt

ftrace: Remove check for HAVE_FUNCTION_TRACE_MCOUNT_TEST

2014-07-18T17:57:01Z

function_trace_stop is no longer used to disable function tracing. This means that archs are no longer limited if it does not support checking this variable in the mcount trampoline. No need to use the list_func for archs that do not support this obsolete method. Acked-by: James Hogan Reviewed-by: Masami Hiramatsu Signed-off-by: Steven Rostedt

ftrace: Remove ftrace_start/stop()

2014-07-18T17:56:59Z

There are no more kernel users of ftrace_stop() and ftrace_start(). Remove them. Reviewed-by: Masami Hiramatsu Signed-off-by: Steven Rostedt

ftrace-graph: Remove dependency of ftrace_stop() from ftrace_graph_stop()

2014-07-17T13:45:07Z

ftrace_stop() is going away as it disables parts of function tracing that affects users that should not be affected. But ftrace_graph_stop() is built on ftrace_stop(). Here's another example of killing all of function tracing because something went wrong with function graph tracing. Instead of disabling all users of function tracing on function graph error, disable only function graph tracing. A new function is created called ftrace_graph_is_dead(). This is called in strategic paths to prevent function graph from doing more harm and allowing at least a warning to be printed before the system crashes. NOTE: ftrace_stop() is still used until all the archs are converted over to use ftrace_graph_is_dead(). After that, ftrace_stop() will be removed. Reviewed-by: Masami Hiramatsu Cc: Frederic Weisbecker Signed-off-by: Steven Rostedt

ftrace: Allow archs to specify if they need a separate function graph trampoline

2014-07-16T15:01:24Z

Currently if an arch supports function graph tracing, the core code will just assign the function graph trampoline to the function graph addr that gets called. But as the old method for function graph tracing always calls the function trampoline first and that calls the function graph trampoline, some archs may have the function graph trampoline dependent on operations that were done in the function trampoline. This causes function graph tracer to break on those archs. Instead of having the default be to set the function graph ftrace_ops to the function graph trampoline, have it instead just set it to zero which will keep it from jumping to a trampoline that is not set up to be jumped directly too. Link: http://lkml.kernel.org/r/53BED155.9040607@nvidia.com Reported-by: Tuomas Tynkkynen Tested-by: Tuomas Tynkkynen Signed-off-by: Steven Rostedt