perf record: Add support for sampling taken branch

This patch adds a new option to enable taken branch stack
sampling, i.e., leverage the PERF_SAMPLE_BRANCH_STACK feature
of perf_events.

There is a new option to active this mode: -b.
It is possible to pass a set of filters to select the type of
branches to sample.

The following filters are available:

 - any : any type of branches
 - any_call : any function call or system call
 - any_ret : any function return or system call return
 - any_ind : any indirect branch
 - u:  only when the branch target is at the user level
 - k: only when the branch target is in the kernel
 - hv: only when the branch target is in the hypervisor

Filters can be combined by passing a comma separated list
to the option:

$ perf record -b any_call,u -e cycles:u branchy

Signed-off-by: Roberto Agostino Vitillo <ravitillo@lbl.gov>
Signed-off-by: Stephane Eranian <eranian@google.com>
Cc: peterz@infradead.org
Cc: acme@redhat.com
Cc: robert.richter@amd.com
Cc: ming.m.lin@intel.com
Cc: andi@firstfloor.org
Cc: asharma@fb.com
Cc: vweaver1@eecs.utk.edu
Cc: khandual@linux.vnet.ibm.com
Cc: dsahern@gmail.com
Link: http://lkml.kernel.org/r/1328826068-11713-13-git-send-email-eranian@google.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 25 insertions, 0 deletions

diff --git a/tools/perf/Documentation/perf-record.txt b/tools/perf/Documentation/perf-record.txt
index a5766b4b0125..60bddaf0e5bd 100644
--- a/tools/perf/Documentation/perf-record.txt
+++ b/tools/perf/Documentation/perf-record.txt
@@ -152,6 +152,31 @@ an empty cgroup (monitor all the time) using, e.g., -G foo,,bar. Cgroups must ha
 corresponding events, i.e., they always refer to events defined earlier on the command
 line.
 
+-b::
+--branch-stack::
+Enable taken branch stack sampling. Each sample captures a series of consecutive
+taken branches. The number of branches captured with each sample depends on the
+underlying hardware, the type of branches of interest, and the executed code.
+It is possible to select the types of branches captured by enabling filters. The
+following filters are defined:
+
+        -  any :  any type of branches
+        - any_call: any function call or system call
+        - any_ret: any function return or system call return
+        - any_ind: any indirect branch
+        - u:  only when the branch target is at the user level
+        - k: only when the branch target is in the kernel
+        - hv: only when the target is at the hypervisor level
+
++
+At least one of any, any_call, any_ret, any_ind must be provided. The privilege levels may
+be ommitted, in which case, the privilege levels of the associated event are applied to the
+branch filter. Both kernel (k) and hypervisor (hv) privilege levels are subject to
+permissions.  When sampling on multiple events, branch stack sampling is enabled for all
+the sampling events. The sampled branch type is the same for all events.
+Note that taken branch sampling may not be available on all processors.
+The various filters must be specified as a comma separated list: -b any_ret,u,k
+
 SEE ALSO
 --------
 linkperf:perf-stat[1], linkperf:perf-list[1]