Factor out common code in functions synthesizing event samples i.e.
intel_pt_synth_branch_sample(), intel_pt_synth_instruction_sample() and
intel_pt_synth_transaction_sample().
Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Link: http://lkml.kernel.org/r/1495786658-18063-27-git-send-email-adrian.hunter@intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Add a field to display the content the raw_data of a synthesized event.
Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Link: http://lkml.kernel.org/r/1495786658-18063-22-git-send-email-adrian.hunter@intel.com
[ Resolved conflict with 106dacd86f ("perf script: Support -F brstackoff,dso") ]
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Instruction trace decoders such as Intel PT may have additional information
recorded in the trace. For example, Intel PT has power information and a
there is a new instruction 'ptwrite' that can write a value into a PTWRITE
trace packet.
Such information may be associated with an IP and so can be treated as a
sample (PERF_RECORD_SAMPLE). Custom data can be incorporated in the
sample as raw_data (PERF_SAMPLE_RAW).
However a means of identifying the raw data format is needed. That will
be done by synthesizing an attribute for it.
So add an attribute type for custom synthesized events. Different
synthesized events will be identified by the attribute 'config'.
Committer notes:
Start those PERF_TYPE_ after the PMU range, i.e. after (INT_MAX + 1U),
i.e. after perf_pmu_register() -> idr_alloc(end=0).
Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Link: http://lkml.kernel.org/r/1498040239-32418-1-git-send-email-adrian.hunter@intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Add ptwrite to the op code map and the perf tools new instructions test.
To run the test:
$ tools/perf/perf test "x86 ins"
39: Test x86 instruction decoder - new instructions : Ok
Or to see the details:
$ tools/perf/perf test -v "x86 ins" 2>&1 | grep ptwrite
For information about ptwrite, refer the Intel SDM.
Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
Link: http://lkml.kernel.org/r/1495180230-19367-1-git-send-email-adrian.hunter@intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Trivial fix to typo in jvmti_close() warnx warning message.
Signed-off-by: Colin King <colin.king@canonical.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Dan Carpenter <dan.carpenter@oracle.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lkml.kernel.org/r/20170627124917.19151-1-colin.king@canonical.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Finally can nuke this function, no more users.
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Wang Nan <wangnan0@huawei.com>
Link: http://lkml.kernel.org/n/tip-eivvvzn8ie6w42gy3batxoy7@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Just warn the user and ignore those values.
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Wang Nan <wangnan0@huawei.com>
Link: http://lkml.kernel.org/n/tip-tbf60nj3ierm6hrkhpothymx@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
To consolidate the error reporting facility.
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Wang Nan <wangnan0@huawei.com>
Link: http://lkml.kernel.org/n/tip-b41iot1094katoffdf19w9zk@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Now everything uses pr_warning(), so ditch it.
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Wang Nan <wangnan0@huawei.com>
Link: http://lkml.kernel.org/n/tip-hv8r0mgdhk73wtfq3zrhavgx@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Convert sole user of warning() in this file to pr_warning(),
consolidating error reporting facilities.
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Wang Nan <wangnan0@huawei.com>
Link: http://lkml.kernel.org/n/tip-3y7yf6v673ujl2rcs34tzv8n@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
warning() is going away, consolidating error reporting.
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Wang Nan <wangnan0@huawei.com>
Link: http://lkml.kernel.org/n/tip-5r3636cwl4z1varo90mervai@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Complete the switch to using te pr_{warning,error,etc} error reporting
facilities.
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Wang Nan <wangnan0@huawei.com>
Link: http://lkml.kernel.org/n/tip-3l9gr6237b4aqyo0rsspixe2@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
And switch from warning() to pr_warning(), to elliminate another
duplication: too many error reporting facilities.
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Wang Nan <wangnan0@huawei.com>
Link: http://lkml.kernel.org/n/tip-pkzcjrhek3uuqc4i5i9ealwd@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
The warning(str_error_r(errno)) pattern can be replaced with a function,
do it.
And while at it use pr_warning(), we have way too many error reporting
facilities, time to drop some, starting with the one we got from the git
sources.
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Wang Nan <wangnan0@huawei.com>
Link: http://lkml.kernel.org/n/tip-lbak5npj1ri1uuvf1en3c0p0@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
This patch adds platform dependency into the test case 15
(perf_event_attr). It is based on a suggestion from Jiri Olsa.
Add a new optional attribute named 'arch' in the [config] section of the
test case file. It is a comma separated list of architecture names this
test can be executed on. For example:
arch = x86_64,alpha,ppc
If this attribute is missing the test is executed on any platform. This
does not break existing behavior.
The values listed for this attribute should be identical to uname -m
output.
If the list starts with an exclamation mark (!) the comparison is
inverted, for example for
arch = !s390x,ppc
the test is not executed on s390x or ppc platforms. The exclamation
mark must be at the beginnning of the list.
Here is an example debug output:
[root@s35lp76]# fgrep arch tests/attr/test-stat-C2
arch = x86_64,alpha,ppc
[root@s35lp76]# PERF_TEST_ATTR=/tmp /usr/bin/python2 ./tests/attr.py \
-d ./tests/attr/ -p ./perf -vvvvv -t test-stat-C1
provides the following output:
running './tests/attr//test-stat-C1'
test limitation 'x86_64,alpha,ppc' <--- new
loading expected events
Event event:base-stat
fd = 1
group_fd = -1
.....
Here is the output when a test is skipped:
[root@s35lp76]# fgrep arch tests/attr/test-stat-C1
arch = !s390x
[root@s35lp76]# PERF_TEST_ATTR=/tmp /usr/bin/python2 ./tests/attr.py \
-d ./tests/attr/ -p ./perf -vvvvv -t test-stat-C1
provides the following output:
test limitation '!s390x' <--- new
skipped [s390x] './tests/attr//test-stat-C1' <--- new
The test is skipped with return code 0.
Suggested-and-Acked-by: Jiri Olsa <jolsa@redhat.com>
Reviewed-by: Arnaldo Carvalho de Melo <acme@kernel.org>
Signed-off-by: Thomas Richter <tmricht@linux.vnet.ibm.com>
Cc: Hendrik Brueckner <brueckner@linux.vnet.ibm.com>
Cc: linux-s390@vger.kernel.org
Link: http://lkml.kernel.org/r/20170622073625.86762-1-tmricht@linux.vnet.ibm.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
'transactions_sample_type' is needed to correctly inject transactions
samples but it was not being set. Set it from the event sample type.
Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Link: http://lkml.kernel.org/r/1495786658-18063-18-git-send-email-adrian.hunter@intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
'initial_skip' is checked inside the sample synthesis functions which means
it is actually being done twice for 'instructions' and 'transactions'
samples. Remove the redundant checks.
Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Link: http://lkml.kernel.org/r/1495786658-18063-17-git-send-email-adrian.hunter@intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Future proof CBR packet decoding by passing through also the undefined
'reserved' byte in the packet payload.
Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Link: http://lkml.kernel.org/r/1495786658-18063-15-git-send-email-adrian.hunter@intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Add decoder support for PTWRITE, MWAIT, PWRE, PWRX and EXSTOP packets. This
patch only affects the decoder, so the tools still do not select or consume
the new information. That is added in subsequent patches.
Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Link: http://lkml.kernel.org/r/1495786658-18063-14-git-send-email-adrian.hunter@intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Branch tracing is enabled by default, so a fake config bit called 'pt'
(pass-through) was added to allow the 'branch enable' bit to have affect.
Add default config 'pt,branch' which will allow users to disable branch
tracing using 'branch=0' instead of having to specify 'pt,branch=0'.
Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Link: http://lkml.kernel.org/r/1495786658-18063-12-git-send-email-adrian.hunter@intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
The kernel now supports the disabling of branch tracing, however the
decoder assumes branch tracing is always enabled. Pass through a parameter
to indicate whether branch tracing is enabled and use it to avoid cases
when the decoder is expecting branch packets. There are 2 such cases.
First, FUP packets which can bind to an IP even when there is no branch
tracing. Secondly, the decoder will try to use branch packets to find an IP
to start decoding or to recover from errors.
Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Link: http://lkml.kernel.org/r/1495786658-18063-11-git-send-email-adrian.hunter@intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Sometimes a FUP packet is associated with a TSX transaction and a flag is
set to indicate that. Ensure that flag is cleared on any error condition
because at that point the decoder can no longer assume it is correct.
Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: stable@vger.kernel.org
Link: http://lkml.kernel.org/r/1495786658-18063-9-git-send-email-adrian.hunter@intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
The decoder will try to use branch packets to find an IP to start decoding
or to recover from errors. Currently the FUP packet is used only in the
case of an overflow, however there is no reason for that to be a special
case. So just use FUP always when scanning for an IP.
Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: stable@vger.kernel.org
Link: http://lkml.kernel.org/r/1495786658-18063-8-git-send-email-adrian.hunter@intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Intel PT uses IP compression based on the last IP. For decoding purposes,
'last IP' is not updated when a branch target has been suppressed, which is
indicated by IPBytes == 0. IPBytes is stored in the packet 'count', so
ensure never to set 'last_ip' when packet 'count' is zero.
Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: stable@vger.kernel.org
Link: http://lkml.kernel.org/r/1495786658-18063-7-git-send-email-adrian.hunter@intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Intel PT uses IP compression based on the last IP. For decoding
purposes, 'last IP' is considered to be reset to zero whenever there is
a synchronization packet (PSB). The decoder wasn't doing that, and was
treating the zero value to mean that there was no last IP, whereas
compression can be done against the zero value. Fix by setting last_ip
to zero when a PSB is received and keep track of have_last_ip.
Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: stable@vger.kernel.org
Link: http://lkml.kernel.org/r/1495786658-18063-6-git-send-email-adrian.hunter@intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
The decoder uses its current timestamp in samples. Usually that is a
timestamp that has already passed, but in some cases it is a timestamp
for a branch that the decoder is walking towards, and consequently
hasn't reached. Improve that situation by using the pkt_state to
determine when to use the current or previous timestamp.
Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: stable@vger.kernel.org
Link: http://lkml.kernel.org/r/1495786658-18063-3-git-send-email-adrian.hunter@intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Porting PPC to libdw only needs an architecture-specific hook to move
the register state from perf to libdw.
The ARM and x86 architectures already use libdw, and it is useful to
have as much common code for the unwinder as possible. Mark Wielaard
has contributed a frame-based unwinder to libdw, so that unwinding works
even for binaries that do not have CFI information. In addition,
libunwind is always preferred to libdw by the build machinery so this
cannot introduce regressions on machines that have both libunwind and
libdw installed.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Acked-by: Milian Wolff <milian.wolff@kdab.com>
Acked-by: Ravi Bangoria <ravi.bangoria@linux.vnet.ibm.com>
Cc: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Cc: linuxppc-dev@lists.ozlabs.org
Link: http://lkml.kernel.org/r/1496312681-20133-1-git-send-email-pbonzini@redhat.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Implementing a new --smi-cost mode in perf stat to measure SMI cost.
During the measurement, the /sys/device/cpu/freeze_on_smi will be set.
The measurement can be done with one counter (unhalted core cycles), and
two free running MSR counters (IA32_APERF and SMI_COUNT).
In practice, the percentages of SMI core cycles should be more useful
than absolute value. So the output will be the percentage of SMI core
cycles and SMI#. metric_only will be set by default.
SMI cycles% = (aperf - unhalted core cycles) / aperf
Here is an example output.
Performance counter stats for 'sudo echo ':
SMI cycles% SMI#
0.1% 1
0.010858678 seconds time elapsed
Users who wants to get the actual value can apply additional
--no-metric-only.
Signed-off-by: Kan Liang <Kan.liang@intel.com>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Kan Liang <kan.liang@intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Robert Elliott <elliott@hpe.com>
Cc: Stephane Eranian <eranian@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1495825538-5230-3-git-send-email-kan.liang@intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Curious as to what this was for I looked at /usr/include/ and only some
python headers define this, and it ends up being to enable "extensions"
on some old OSes:
/* Enable extensions on AIX 3, Interix */
I guess we can remove this one safely.
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Wang Nan <wangnan0@huawei.com>
Link: http://lkml.kernel.org/n/tip-omnundlxo2brs552bdl6m0j1@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
While trying to reduce util.[ch] I noticed that fetch_kernel_version()
and fetch_ubuntu_kernel_version() do lots of operations only to check if
they are needed, i.e. it checks if the pointer where to return the
kernel version is NULL only after obtaining the kernel version from
/proc/version_signature or by parsing the results from uname().
Do it earlier not to confuse people reading this code in the future :-)
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Wang Nan <wangnan0@huawei.com>
Link: http://lkml.kernel.org/n/tip-i94qwyekk4tzbu0b9ce1r1mz@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
And make it static, nobody else uses it, if we ever need it in more
places we can carve a new source file for process related methods,
for now lets reduce util.{c,h} a tad more.
Link: http://lkml.kernel.org/n/tip-zgb28rllvypjibw52aaz9p15@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
To simplify the code related to 'ret' variable in cmd_config(),
initialize 'ret' with -1 instead of 0 and use goto to perform resource
release at the end of the function, setting ret to zero just before the
out_err label, as usual in the kernel sources.
Signed-off-by: Taeung Song <treeze.taeung@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: http://lkml.kernel.org/r/1497671202-20495-1-git-send-email-treeze.taeung@gmail.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
show_spec_config() and set_config() can be called multiple times
in the loop in cmd_config().
However, The error cases of them wasn't checked, so fix it.
Reported-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: Taeung Song <treeze.taeung@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: http://lkml.kernel.org/r/1497671197-20450-1-git-send-email-treeze.taeung@gmail.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
The -D/--graph-depth option is to set max graph depth. The following
example traces max 2-depth of page fault handler.
$ sudo perf ftrace -G __do_page_fault -D 2 -- hello
...
0) | __do_page_fault() {
0) 0.063 us | down_read_trylock();
0) 0.251 us | find_vma();
0) 5.374 us | handle_mm_fault();
0) 0.054 us | up_read();
0) 7.463 us | }
...
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: kernel-team@lge.com
Link: http://lkml.kernel.org/r/20170618142302.25390-4-namhyung@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
The 'perf ftrace' command fails to reset tracer after finishing
recording like below:
$ sudo perf ftrace -v hello
write 'nop' to tracing/current_tracer failed: Device or resource busy
...
This is because the trace_pipe file is open in pager process. Move the
pager setup to before opening the file.
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: kernel-team@lge.com
Fixes: 583359646f ("perf ftrace: Use pager for displaying result")
Link: http://lkml.kernel.org/r/20170618142302.25390-2-namhyung@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
It'd be better for debugging to show an error message when it fails to
setup ftrace for some reason.
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: kernel-team@lge.com
Link: http://lkml.kernel.org/r/20170618142302.25390-1-namhyung@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
The idea here is to make AutoFDO easier in cloud environment with ASLR.
It's easiest to show how this is useful by example. I built a small test
akin to "while(1) { do_nothing(); }" where the do_nothing function is
loaded from a dso:
$ cat burncpu.cpp
#include <dlfcn.h>
int main() {
void* handle = dlopen("./dso.so", RTLD_LAZY);
if (!handle) return -1;
typedef void (*fp)();
fp do_nothing = (fp) dlsym(handle, "do_nothing");
while(1) {
do_nothing();
}
}
$ cat dso.cpp
extern "C" void do_nothing() {}
$ cat build.sh
#!/bin/bash
g++ -shared dso.cpp -o dso.so
g++ burncpu.cpp -o burncpu -ldl
I sampled the execution of this program with perf record -b.
Using the existing "brstack,dso", we get absolute addresses that are
affected by ASLR, and could be different on different hosts. The address
does not uniquely identify a branch/target in the binary:
$ perf script -F brstack,dso | sed 's/\/0 /\/0\n/g' | grep burncpu | grep dso.so | head -n 1
0x7f967139b6aa(/tmp/burncpu/dso.so)/0x4006b1(/tmp/burncpu/exe)/P/-/-/0
Using the existing "brstacksym,dso" is a little better, because the
symbol plus offset and dso name *does* uniquely identify a branch/target
in the binary. Ultimately, however, AutoFDO wants a simple offset into
the binary, so we'd have to undo all the work perf did to symbolize in
the first place:
$ perf script -F brstacksym,dso | sed 's/\/0 /\/0\n/g' | grep burncpu | grep dso.so | head -n 1
do_nothing+0x5(/tmp/burncpu/dso.so)/main+0x44(/tmp/burncpu/exe)/P/-/-/0
With the new "brstackoff,dso" we get what we need: a simple offset into a
specific dso/binary that uniquely identifies a branch/target:
$ perf script -F brstackoff,dso | sed 's/\/0 /\/0\n/g' | grep burncpu | grep dso.so | head -n 1
0x6aa(/tmp/burncpu/dso.so)/0x4006b1(/tmp/burncpu/exe)/P/-/-/0
Signed-off-by: Mark Santaniello <marksan@fb.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20170619163825.2012979-2-marksan@fb.com
[ Updated documentation about 'brstackoff' using text from above ]
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
