This means the user can't access /proc/kallsyms, for instance, because
/proc/sys/kernel/kptr_restrict is set to 1.
Instead leave the ref_reloc_sym as NULL and code using it will cope.
This allows 'perf trace' to work on such systems for !root, the only
issue would be when trying to resolve kernel symbols, which happens,
for instance, in some libtracevent plugins. A warning for that case
will be provided in the next patch in this series.
Noticed in Ubuntu 16.04, that comes with kptr_restrict=1.
Reported-by: Milian Wolff <milian.wolff@kdab.com>
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-knpu3z4iyp2dxpdfm798fac4@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Pull perf/core improvements and fixes from Arnaldo Carvalho de Melo:
User visible changes:
- Honour the kernel.perf_event_max_stack knob more precisely by not counting
PERF_CONTEXT_{KERNEL,USER} when deciding when to stop adding entries to
the perf_sample->ip_callchain[] array (Arnaldo Carvalho de Melo)
- Fix identation of 'stalled-backend-cycles' in 'perf stat' (Namhyung Kim)
- Update runtime using 'cpu-clock' event in 'perf stat' (Namhyung Kim)
- Use 'cpu-clock' for cpu targets in 'perf stat' (Namhyung Kim)
- Avoid fractional digits for integer scales in 'perf stat' (Andi Kleen)
- Store vdso buildid unconditionally, as it appears in callchains and
we're not checking those when creating the build-id table, so we
end up not being able to resolve VDSO symbols when doing analysis
on a different machine than the one where recording was done, possibly
of a different arch even (arm -> x86_64) (He Kuang)
Infrastructure changes:
- Generalize max_stack sysctl handler, will be used for configuring
multiple kernel knobs related to callchains (Arnaldo Carvalho de Melo)
Cleanups:
- Introduce DSO__NAME_KALLSYMS and DSO__NAME_KCORE, to stop using
open coded strings (Masami Hiramatsu)
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Currently only the task-clock event updates the runtime_nsec so it
cannot show the metric when using cpu-clock events. However cpu clock
works basically same as task-clock, so no need to not update the runtime
IMHO.
Before:
# perf stat -a -e cpu-clock,context-switches,page-faults,cycles sleep 0.1
Performance counter stats for 'system wide':
1217.759506 cpu-clock (msec)
93 context-switches
61 page-faults
18,958,022 cycles
0.101393794 seconds time elapsed
After:
Performance counter stats for 'system wide':
1220.471884 cpu-clock (msec) # 12.013 CPUs utilized
118 context-switches # 0.097 K/sec
59 page-faults # 0.048 K/sec
17,941,247 cycles # 0.015 GHz
0.101594777 seconds time elapsed
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1463119263-5569-2-git-send-email-namhyung@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Pull perf updates from Ingo Molnar:
"Bigger kernel side changes:
- Add backwards writing capability to the perf ring-buffer code,
which is preparation for future advanced features like robust
'overwrite support' and snapshot mode. (Wang Nan)
- Add pause and resume ioctls for the perf ringbuffer (Wang Nan)
- x86 Intel cstate code cleanups and reorgnization (Thomas Gleixner)
- x86 Intel uncore and CPU PMU driver updates (Kan Liang, Peter
Zijlstra)
- x86 AUX (Intel PT) related enhancements and updates (Alexander
Shishkin)
- x86 MSR PMU driver enhancements and updates (Huang Rui)
- ... and lots of other changes spread out over 40+ commits.
Biggest tooling side changes:
- 'perf trace' features and enhancements. (Arnaldo Carvalho de Melo)
- BPF tooling updates (Wang Nan)
- 'perf sched' updates (Jiri Olsa)
- 'perf probe' updates (Masami Hiramatsu)
- ... plus 200+ other enhancements, fixes and cleanups to tools/
The merge commits, the shortlog and the changelogs contain a lot more
details"
* 'perf-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (249 commits)
perf/core: Disable the event on a truncated AUX record
perf/x86/intel/pt: Generate PMI in the STOP region as well
perf buildid-cache: Use lsdir() for looking up buildid caches
perf symbols: Use lsdir() for the search in kcore cache directory
perf tools: Use SBUILD_ID_SIZE where applicable
perf tools: Fix lsdir to set errno correctly
perf trace: Move seccomp args beautifiers to tools/perf/trace/beauty/
perf trace: Move flock op beautifier to tools/perf/trace/beauty/
perf build: Add build-test for debug-frame on arm/arm64
perf build: Add build-test for libunwind cross-platforms support
perf script: Fix export of callchains with recursion in db-export
perf script: Fix callchain addresses in db-export
perf script: Fix symbol insertion behavior in db-export
perf symbols: Add dso__insert_symbol function
perf scripting python: Use Py_FatalError instead of die()
perf tools: Remove xrealloc and ALLOC_GROW
perf help: Do not use ALLOC_GROW in add_cmd_list
perf pmu: Make pmu_formats_string to check return value of strbuf
perf header: Make topology checkers to check return value of strbuf
perf tools: Make alias handler to check return value of strbuf
...
After 0161028b7c ("perf/core: Change the default paranoia level to 2")
'perf stat' fails for users without CAP_SYS_ADMIN, so just use
'perf_evsel__fallback()' to have the same behaviour as 'perf record',
i.e. set perf_event_attr.exclude_kernel to 1.
Now:
[acme@jouet linux]$ perf stat usleep 1
Performance counter stats for 'usleep 1':
0.352536 task-clock:u (msec) # 0.423 CPUs utilized
0 context-switches:u # 0.000 K/sec
0 cpu-migrations:u # 0.000 K/sec
49 page-faults:u # 0.139 M/sec
309,407 cycles:u # 0.878 GHz
243,791 instructions:u # 0.79 insn per cycle
49,622 branches:u # 140.757 M/sec
3,884 branch-misses:u # 7.83% of all branches
0.000834174 seconds time elapsed
[acme@jouet linux]$
Reported-by: Ingo Molnar <mingo@kernel.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Kees Cook <keescook@chromium.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Wang Nan <wangnan0@huawei.com>
Link: http://lkml.kernel.org/n/tip-b20jmx4dxt5hpaa9t2rroi0o@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Now with the default for the kernel.perf_event_paranoid sysctl being 2 [1]
we need to fall back to :u, i.e. to set perf_event_attr.exclude_kernel
to 1.
Before:
[acme@jouet linux]$ perf record usleep 1
Error:
You may not have permission to collect stats.
Consider tweaking /proc/sys/kernel/perf_event_paranoid,
which controls use of the performance events system by
unprivileged users (without CAP_SYS_ADMIN).
The current value is 2:
-1: Allow use of (almost) all events by all users
>= 0: Disallow raw tracepoint access by users without CAP_IOC_LOCK
>= 1: Disallow CPU event access by users without CAP_SYS_ADMIN
>= 2: Disallow kernel profiling by users without CAP_SYS_ADMIN
[acme@jouet linux]$
After:
[acme@jouet linux]$ perf record usleep 1
[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 0.016 MB perf.data (7 samples) ]
[acme@jouet linux]$ perf evlist
cycles:u
[acme@jouet linux]$ perf evlist -v
cycles:u: size: 112, { sample_period, sample_freq }: 4000, sample_type: IP|TID|TIME|PERIOD, disabled: 1, inherit: 1, exclude_kernel: 1, mmap: 1, comm: 1, freq: 1, enable_on_exec: 1, task: 1, sample_id_all: 1, exclude_guest: 1, mmap2: 1, comm_exec: 1
[acme@jouet linux]$
And if the user turns on verbose mode, an explanation will appear:
[acme@jouet linux]$ perf record -v usleep 1
Warning:
kernel.perf_event_paranoid=2, trying to fall back to excluding kernel samples
mmap size 528384B
[ perf record: Woken up 1 times to write data ]
Looking at the vmlinux_path (8 entries long)
Using /lib/modules/4.6.0-rc7+/build/vmlinux for symbols
[ perf record: Captured and wrote 0.016 MB perf.data (7 samples) ]
[acme@jouet linux]$
[1] 0161028b7c ("perf/core: Change the default paranoia level to 2")
Reported-by: Ingo Molnar <mingo@kernel.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Kees Cook <keescook@chromium.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Wang Nan <wangnan0@huawei.com>
Link: http://lkml.kernel.org/n/tip-b20jmx4dxt5hpaa9t2rroi0o@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
We were showing a hardcoded default value for the kernel.perf_event_paranoid
sysctl, now that it became more paranoid (1 -> 2 [1]), this would need to be
updated, instead show the current value:
[acme@jouet linux]$ perf record ls
Error:
You may not have permission to collect stats.
Consider tweaking /proc/sys/kernel/perf_event_paranoid,
which controls use of the performance events system by
unprivileged users (without CAP_SYS_ADMIN).
The current value is 2:
-1: Allow use of (almost) all events by all users
>= 0: Disallow raw tracepoint access by users without CAP_IOC_LOCK
>= 1: Disallow CPU event access by users without CAP_SYS_ADMIN
>= 2: Disallow kernel profiling by users without CAP_SYS_ADMIN
[acme@jouet linux]$
[1] 0161028b7c ("perf/core: Change the default paranoia level to 2")
Reported-by: Ingo Molnar <mingo@kernel.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Kees Cook <keescook@chromium.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Wang Nan <wangnan0@huawei.com>
Link: http://lkml.kernel.org/n/tip-0gc4rdpg8d025r5not8s8028@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
The readdir() function is thread safe as long as just one thread uses a
DIR, which is the case when parsing tracepoint event definitions, to
avoid breaking the build with glibc-2.23.90 (upcoming 2.24), use it
instead of readdir_r().
See: http://man7.org/linux/man-pages/man3/readdir.3.html
"However, in modern implementations (including the glibc implementation),
concurrent calls to readdir() that specify different directory streams
are thread-safe. In cases where multiple threads must read from the
same directory stream, using readdir() with external synchronization is
still preferable to the use of the deprecated readdir_r(3) function."
Noticed while building on a Fedora Rawhide docker container.
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-wddn49r6bz6wq4ee3dxbl7lo@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
The readdir() function is thread safe as long as just one thread uses a
DIR, which is the case in thread_map, so, to avoid breaking the build
with glibc-2.23.90 (upcoming 2.24), use it instead of readdir_r().
See: http://man7.org/linux/man-pages/man3/readdir.3.html
"However, in modern implementations (including the glibc implementation),
concurrent calls to readdir() that specify different directory streams
are thread-safe. In cases where multiple threads must read from the
same directory stream, using readdir() with external synchronization is
still preferable to the use of the deprecated readdir_r(3) function."
Noticed while building on a Fedora Rawhide docker container.
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-del8h2a0f40z75j4r42l96l0@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
The readdir() function is thread safe as long as just one thread uses a
DIR, which is the case in 'perf script', so, to avoid breaking the build
with glibc-2.23.90 (upcoming 2.24), use it instead of readdir_r().
See: http://man7.org/linux/man-pages/man3/readdir.3.html
"However, in modern implementations (including the glibc implementation),
concurrent calls to readdir() that specify different directory streams
are thread-safe. In cases where multiple threads must read from the
same directory stream, using readdir() with external synchronization is
still preferable to the use of the deprecated readdir_r(3) function."
Noticed while building on a Fedora Rawhide docker container.
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-mt3xz7n2hl49ni2vx7kuq74g@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
The readdir() function is thread safe as long as just one thread uses a
DIR, which is the case when synthesizing events for pre-existing threads
by traversing /proc, so, to avoid breaking the build with glibc-2.23.90
(upcoming 2.24), use it instead of readdir_r().
See: http://man7.org/linux/man-pages/man3/readdir.3.html
"However, in modern implementations (including the glibc implementation),
concurrent calls to readdir() that specify different directory streams
are thread-safe. In cases where multiple threads must read from the
same directory stream, using readdir() with external synchronization is
still preferable to the use of the deprecated readdir_r(3) function."
Noticed while building on a Fedora Rawhide docker container.
CC /tmp/build/perf/util/event.o
util/event.c: In function '__event__synthesize_thread':
util/event.c:466:2: error: 'readdir_r' is deprecated [-Werror=deprecated-declarations]
while (!readdir_r(tasks, &dirent, &next) && next) {
^~~~~
In file included from /usr/include/features.h:368:0,
from /usr/include/stdint.h:25,
from /usr/lib/gcc/x86_64-redhat-linux/6.0.0/include/stdint.h:9,
from /git/linux/tools/include/linux/types.h:6,
from util/event.c:1:
/usr/include/dirent.h:189:12: note: declared here
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-i1vj7nyjp2p750rirxgrfd3c@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
When an IP with an unresolved symbol occurs in the callchain more than
once (ie. recursion), then duplicate symbols can be created because
the callchain nodes are never updated after they are first created.
To fix this issue we call dso__find_symbol whenever we encounter a NULL
symbol, in case we already added a symbol at that IP since we started
traversing the callchain.
This change prevents duplicate symbols from being exported when duplicate
IPs are present in the callchain.
Signed-off-by: Chris Phlipot <cphlipot0@gmail.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1462937209-6032-5-git-send-email-cphlipot0@gmail.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Remove the call to map_ip() to adjust al.addr, because it has already
been called when assembling the callchain, in:
thread__resolve_callchain_sample(perf_sample)
add_callchain_ip(ip = perf_sample->callchain->ips[j])
thread__find_addr_location(addr = ip)
thread__find_addr_map(addr) {
al->addr = addr
if (al->map)
al->addr = al->map->map_ip(al->map, al->addr);
}
Calling it a second time can result in incorrect addresses being used.
This can have effects such as duplicate symbols being created and
exported.
Signed-off-by: Chris Phlipot <cphlipot0@gmail.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1462937209-6032-4-git-send-email-cphlipot0@gmail.com
[ Show the callchain where it is done, to help reviewing this change down the line ]
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
The current method for inserting symbols is to use the symbols__insert()
function. However symbols__insert() does not update the dso symbol
cache. This causes problems in the following scenario:
1. symbol not found at addr using dso__find_symbol
2. symbol inserted at addr using the existing symbols__insert function
3. symbol still not found at addr using dso__find_symbol() because cache isn't
updated. This is undesired behavior.
The undesired behavior in (3) is addressed by creating a new function,
dso__insert_symbol() to both insert the symbol and update the symbol
cache if necessary.
If dso__insert_symbol() is used in (2) instead of symbols__insert(),
then the undesired behavior in (3) is avoided.
Signed-off-by: Chris Phlipot <cphlipot0@gmail.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1462937209-6032-2-git-send-email-cphlipot0@gmail.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Pull perf/core improvements and fixes from Arnaldo Carvalho de Melo:
User visible changes:
- Recording 'dwarf' callchains do not need DWARF unwinding support (He Kuang)
- Print recently added perf_event_attr.write_backward bit flag in -vv
verbose mode (Arnaldo Carvalho de Melo)
- Fix incorrect python db-export error message in 'perf script' (Chris Phlipot)
- Fix handling of zero-length symbols (Chris Phlipot)
- perf stat: Scale values by unit before metrics (Andi Kleen)
Infrastructure changes:
- Rewrite strbuf not to die(), making tools using it to check its
return value instead (Masami Hiramatsu)
- Support reading from backward ring buffer, add a 'perf test' entry
for it (Wang Nan)
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
On some architectures (powerpc in particular), the number of registers
exceeds what can be represented in an integer bitmask. Ensure we
generate the proper bitmask on such platforms.
Fixes: 71ad0f5e4 ("perf tools: Support for DWARF CFI unwinding on post processing")
Signed-off-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Acked-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Make alias handler and sq_quote_argv to check the return value of strbuf
APIs.
In sq_quote_argv() calls die(), but this fix handles strbuf failure as a
special case and returns to caller, since the caller - handle_alias()
also has to check the return value of other strbuf APIs and those checks
can be merged to one if() statement.
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20160510054725.6158.84597.stgit@devbox
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
This change introduces a fix to symbols__find, so that it is able to
find symbols of length zero (where start == end).
The current code has the following problem:
- The current implementation of symbols__find is unable to find any symbols
of length zero.
- The db-export framework explicitly creates zero length symbols at
locations where no symbol currently exists.
The combination of the two above behaviors results in behavior similar
to the example below.
1. addr_location is created for a sample, but symbol is unable to be
resolved.
2. db export creates an "unknown" symbol of length zero at that address
and inserts it into the dso.
3. A new sample comes in at the same address, but symbol__find is unable
to find the zero length symbol, so it is still unresolved.
4. db export sees the symbol is unresolved, and allocated a duplicate
symbol, even though it already did this in step 2.
This behavior continues every time an address without symbol information
is seen, which causes a very large number of these symbols to be
allocated.
The effect of this fix can be observed by looking at the contents of an
exported database before/after the fix (generated with
scripts/python/export-to-postgresql.py)
Ex.
BEFORE THE CHANGE:
example_db=# select count(*) from symbols;
count
--------
900213
(1 row)
example_db=# select count(*) from symbols where symbols.name='unknown';
count
--------
897355
(1 row)
example_db=# select count(*) from symbols where symbols.name!='unknown';
count
-------
2858
(1 row)
AFTER THE CHANGE:
example_db=# select count(*) from symbols;
count
-------
25217
(1 row)
example_db=# select count(*) from symbols where name='unknown';
count
-------
22359
(1 row)
example_db=# select count(*) from symbols where name!='unknown';
count
-------
2858
(1 row)
Signed-off-by: Chris Phlipot <cphlipot0@gmail.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1462612620-25008-1-git-send-email-cphlipot0@gmail.com
[ Moved the test to later in the rb_tree tests, as this not the likely case ]
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Now we can see if it is set when using verbose mode in various tools,
such as 'perf test':
# perf test -vv back
45: Test backward reading from ring buffer :
--- start ---
<SNIP>
------------------------------------------------------------
perf_event_attr:
type 2
size 112
config 0x98
{ sample_period, sample_freq } 1
sample_type IP|TID|TIME|CPU|PERIOD|RAW
disabled 1
mmap 1
comm 1
task 1
sample_id_all 1
exclude_guest 1
mmap2 1
comm_exec 1
write_backward 1
------------------------------------------------------------
sys_perf_event_open: pid 20911 cpu -1 group_fd -1 flags 0x8
<SNIP>
---- end ----
Test backward reading from ring buffer: Ok
#
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Milian Wolff <milian.wolff@kdab.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Wang Nan <wangnan0@huawei.com>
Link: http://lkml.kernel.org/n/tip-kxv05kv9qwl5of7rzfeiiwbv@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
This test checks reading from backward ring buffer.
Test result:
# ~/perf test 'ring buffer'
45: Test backward reading from ring buffer : Ok
The test case is a while loop which calls prctl(PR_SET_NAME) multiple
times. Each prctl should issue 2 events: one PERF_RECORD_SAMPLE, one
PERF_RECORD_COMM.
The first round creates a relative large ring buffer (256 pages). It can
afford all events. Read from it and check the count of each type of
events.
The second round creates a small ring buffer (1 page) and makes it
overwritable. Check the correctness of the buffer.
Signed-off-by: Wang Nan <wangnan0@huawei.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Zefan Li <lizefan@huawei.com>
Cc: pi3orama@163.com
Link: http://lkml.kernel.org/r/1462758471-89706-3-git-send-email-wangnan0@huawei.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
