diff options
author | Linus Torvalds <torvalds@linux-foundation.org> | 2024-01-20 01:25:23 +0300 |
---|---|---|
committer | Linus Torvalds <torvalds@linux-foundation.org> | 2024-01-20 01:25:23 +0300 |
commit | 9d64bf433c53cab2f48a3fff7a1f2a696bc5229a (patch) | |
tree | 0535254c177c27ec34adbc153d494cea9a9625a0 /tools/perf/Documentation | |
parent | 57f22c8dab6b266ae36b89b073a4a33dea71e762 (diff) | |
parent | d988c9f511af71a3445b6a4f3a2c67208ff8e480 (diff) | |
download | linux-9d64bf433c53cab2f48a3fff7a1f2a696bc5229a.tar.xz |
Merge tag 'perf-tools-for-v6.8-1-2024-01-09' of git://git.kernel.org/pub/scm/linux/kernel/git/perf/perf-tools
Pull perf tools updates from Arnaldo Carvalho de Melo:
"Add Namhyung Kim as tools/perf/ co-maintainer, we're taking turns
processing patches, switching roles from perf-tools to perf-tools-next
at each Linux release.
Data profiling:
- Associate samples that identify loads and stores with data
structures. This uses events available on Intel, AMD and others and
DWARF info:
# To get memory access samples in kernel for 1 second (on Intel)
$ perf mem record -a -K --ldlat=4 -- sleep 1
# Similar for the AMD (but it requires 6.3+ kernel for BPF filters)
$ perf mem record -a --filter 'mem_op == load || mem_op == store, ip > 0x8000000000000000' -- sleep 1
Then, amongst several modes of post processing, one can do things like:
$ perf report -s type,typeoff --hierarchy --group --stdio
...
#
# Samples: 10K of events 'cpu/mem-loads,ldlat=4/P, cpu/mem-stores/P, dummy:u'
# Event count (approx.): 602758064
#
# Overhead Data Type / Data Type Offset
# ........................... ............................
#
26.09% 3.28% 0.00% long unsigned int
26.09% 3.28% 0.00% long unsigned int +0 (no field)
18.48% 0.73% 0.00% struct page
10.83% 0.02% 0.00% struct page +8 (lru.next)
3.90% 0.28% 0.00% struct page +0 (flags)
3.45% 0.06% 0.00% struct page +24 (mapping)
0.25% 0.28% 0.00% struct page +48 (_mapcount.counter)
0.02% 0.06% 0.00% struct page +32 (index)
0.02% 0.00% 0.00% struct page +52 (_refcount.counter)
0.02% 0.01% 0.00% struct page +56 (memcg_data)
0.00% 0.01% 0.00% struct page +16 (lru.prev)
15.37% 17.54% 0.00% (stack operation)
15.37% 17.54% 0.00% (stack operation) +0 (no field)
11.71% 50.27% 0.00% (unknown)
11.71% 50.27% 0.00% (unknown) +0 (no field)
$ perf annotate --data-type
...
Annotate type: 'struct cfs_rq' in [kernel.kallsyms] (13 samples):
============================================================================
samples offset size field
13 0 640 struct cfs_rq {
2 0 16 struct load_weight load {
2 0 8 unsigned long weight;
0 8 4 u32 inv_weight;
};
0 16 8 unsigned long runnable_weight;
0 24 4 unsigned int nr_running;
1 28 4 unsigned int h_nr_running;
...
$ perf annotate --data-type=page --group
Annotate type: 'struct page' in [kernel.kallsyms] (480 samples):
event[0] = cpu/mem-loads,ldlat=4/P
event[1] = cpu/mem-stores/P
event[2] = dummy:u
===================================================================================
samples offset size field
447 33 0 0 64 struct page {
108 8 0 0 8 long unsigned int flags;
319 13 0 8 40 union {
319 13 0 8 40 struct {
236 2 0 8 16 union {
236 2 0 8 16 struct list_head lru {
236 1 0 8 8 struct list_head* next;
0 1 0 16 8 struct list_head* prev;
};
236 2 0 8 16 struct {
236 1 0 8 8 void* __filler;
0 1 0 16 4 unsigned int mlock_count;
};
236 2 0 8 16 struct list_head buddy_list {
236 1 0 8 8 struct list_head* next;
0 1 0 16 8 struct list_head* prev;
};
236 2 0 8 16 struct list_head pcp_list {
236 1 0 8 8 struct list_head* next;
0 1 0 16 8 struct list_head* prev;
};
};
82 4 0 24 8 struct address_space* mapping;
1 7 0 32 8 union {
1 7 0 32 8 long unsigned int index;
1 7 0 32 8 long unsigned int share;
};
0 0 0 40 8 long unsigned int private;
};
This uses the existing annotate code, calling objdump to do the
disassembly, with improvements to avoid having this take too long,
but longer term a switch to a disassembler library, possibly
reusing code in the kernel will be pursued.
This is the initial implementation, please use it and report
impressions and bugs. Make sure the kernel-debuginfo packages match
the running kernel. The 'perf report' phase for non short perf.data
files may take a while.
There is a great article about it on LWN:
https://lwn.net/Articles/955709/ - "Data-type profiling for perf"
One last test I did while writing this text, on a AMD Ryzen 5950X,
using a distro kernel, while doing a simple 'find /' on an
otherwise idle system resulted in:
# uname -r
6.6.9-100.fc38.x86_64
# perf -vv | grep BPF_
bpf: [ on ] # HAVE_LIBBPF_SUPPORT
bpf_skeletons: [ on ] # HAVE_BPF_SKEL
# rpm -qa | grep kernel-debuginfo
kernel-debuginfo-common-x86_64-6.6.9-100.fc38.x86_64
kernel-debuginfo-6.6.9-100.fc38.x86_64
#
# perf mem record -a --filter 'mem_op == load || mem_op == store, ip > 0x8000000000000000'
^C[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 2.199 MB perf.data (2913 samples) ]
#
# ls -la perf.data
-rw-------. 1 root root 2346486 Jan 9 18:36 perf.data
# perf evlist
ibs_op//
dummy:u
# perf evlist -v
ibs_op//: type: 11, size: 136, config: 0, { sample_period, sample_freq }: 4000, sample_type: IP|TID|TIME|ADDR|CPU|PERIOD|IDENTIFIER|DATA_SRC|WEIGHT, read_format: ID, disabled: 1, inherit: 1, freq: 1, sample_id_all: 1
dummy:u: type: 1 (PERF_TYPE_SOFTWARE), size: 136, config: 0x9 (PERF_COUNT_SW_DUMMY), { sample_period, sample_freq }: 1, sample_type: IP|TID|TIME|ADDR|CPU|IDENTIFIER|DATA_SRC|WEIGHT, read_format: ID, inherit: 1, exclude_kernel: 1, exclude_hv: 1, mmap: 1, comm: 1, task: 1, mmap_data: 1, sample_id_all: 1, exclude_guest: 1, mmap2: 1, comm_exec: 1, ksymbol: 1, bpf_event: 1
#
# perf report -s type,typeoff --hierarchy --group --stdio
# Total Lost Samples: 0
#
# Samples: 2K of events 'ibs_op//, dummy:u'
# Event count (approx.): 1904553038
#
# Overhead Data Type / Data Type Offset
# ................... ............................
#
73.70% 0.00% (unknown)
73.70% 0.00% (unknown) +0 (no field)
3.01% 0.00% long unsigned int
3.00% 0.00% long unsigned int +0 (no field)
0.01% 0.00% long unsigned int +2 (no field)
2.73% 0.00% struct task_struct
1.71% 0.00% struct task_struct +52 (on_cpu)
0.38% 0.00% struct task_struct +2104 (rcu_read_unlock_special.b.blocked)
0.23% 0.00% struct task_struct +2100 (rcu_read_lock_nesting)
0.14% 0.00% struct task_struct +2384 ()
0.06% 0.00% struct task_struct +3096 (signal)
0.05% 0.00% struct task_struct +3616 (cgroups)
0.05% 0.00% struct task_struct +2344 (active_mm)
0.02% 0.00% struct task_struct +46 (flags)
0.02% 0.00% struct task_struct +2096 (migration_disabled)
0.01% 0.00% struct task_struct +24 (__state)
0.01% 0.00% struct task_struct +3956 (mm_cid_active)
0.01% 0.00% struct task_struct +1048 (cpus_ptr)
0.01% 0.00% struct task_struct +184 (se.group_node.next)
0.01% 0.00% struct task_struct +20 (thread_info.cpu)
0.00% 0.00% struct task_struct +104 (on_rq)
0.00% 0.00% struct task_struct +2456 (pid)
1.36% 0.00% struct module
0.59% 0.00% struct module +952 (kallsyms)
0.42% 0.00% struct module +0 (state)
0.23% 0.00% struct module +8 (list.next)
0.12% 0.00% struct module +216 (syms)
0.95% 0.00% struct inode
0.41% 0.00% struct inode +40 (i_sb)
0.22% 0.00% struct inode +0 (i_mode)
0.06% 0.00% struct inode +76 (i_rdev)
0.06% 0.00% struct inode +56 (i_security)
<SNIP>
perf top/report:
- Don't ignore job control, allowing control+Z + bg to work.
- Add s390 raw data interpretation for PAI (Processor Activity
Instrumentation) counters.
perf archive:
- Add new option '--all' to pack perf.data with DSOs.
- Add new option '--unpack' to expand tarballs.
Initialization speedups:
- Lazily initialize zstd streams to save memory when not using it.
- Lazily allocate/size mmap event copy.
- Lazy load kernel symbols in 'perf record'.
- Be lazier in allocating lost samples buffer in 'perf record'.
- Don't synthesize BPF events when disabled via the command line
(perf record --no-bpf-event).
Assorted improvements:
- Show note on AMD systems that the :p, :pp, :ppp and :P are all the
same, as IBS (Instruction Based Sampling) is used and it is
inherentely precise, not having levels of precision like in Intel
systems.
- When 'cycles' isn't available, fall back to the "task-clock" event
when not system wide, not to 'cpu-clock'.
- Add --debug-file option to redirect debug output, e.g.:
$ perf --debug-file /tmp/perf.log record -v true
- Shrink 'struct map' to under one cacheline by avoiding function
pointers for selecting if addresses are identity or DSO relative,
and using just a byte for some boolean struct members.
- Resolve the arch specific strerrno just once to use in
perf_env__arch_strerrno().
- Reduce memory for recording PERF_RECORD_LOST_SAMPLES event.
Assorted fixes:
- Fix the default 'perf top' usage on Intel hybrid systems, now it
starts with a browser showing the number of samples for Efficiency
(cpu_atom/cycles/P) and Performance (cpu_core/cycles/P). This
behaviour is similar on ARM64, with its respective set of
big.LITTLE processors.
- Fix segfault on build_mem_topology() error path.
- Fix 'perf mem' error on hybrid related to availability of mem event
in a PMU.
- Fix missing reference count gets (map, maps) in the db-export code.
- Avoid recursively taking env->bpf_progs.lock in the 'perf_env'
code.
- Use the newly introduced maps__for_each_map() to add missing
locking around iteration of 'struct map' entries.
- Parse NOTE segments until the build id is found, don't stop on the
first one, ELF files may have several such NOTE segments.
- Remove 'egrep' usage, its deprecated, use 'grep -E' instead.
- Warn first about missing libelf, not libbpf, that depends on
libelf.
- Use alternative to 'find ... -printf' as this isn't supported in
busybox.
- Address python 3.6 DeprecationWarning for string scapes.
- Fix memory leak in uniq() in libsubcmd.
- Fix man page formatting for 'perf lock'
- Fix some spelling mistakes.
perf tests:
- Fail shell tests that needs some symbol in perf itself if it is
stripped. These tests check if a symbol is resolved, if some hot
function is indeed detected by profiling, etc.
- The 'perf test sigtrap' test is currently failing on PREEMPT_RT,
skip it if sleeping spinlocks are detected (using BTF) and point to
the mailing list discussion about it. This test is also being
skipped on several architectures (powerpc, s390x, arm and aarch64)
due to other pending issues with intruction breakpoints.
- Adjust test case perf record offcpu profiling tests for s390.
- Fix 'Setup struct perf_event_attr' fails on s390 on z/VM guest,
addressing issues caused by the fallback from cycles to task-clock
done in this release.
- Fix mask for VG register in the user-regs test.
- Use shellcheck on 'perf test' shell scripts automatically to make
sure changes don't introduce things it flags as problematic.
- Add option to change objdump binary and allow it to be set via
'perf config'.
- Add basic 'perf script', 'perf list --json" and 'perf diff' tests.
- Basic branch counter support.
- Make DSO tests a suite rather than individual.
- Remove atomics from test_loop to avoid test failures.
- Fix call chain match on powerpc for the record+probe_libc_inet_pton
test.
- Improve Intel hybrid tests.
Vendor event files (JSON):
powerpc:
- Update datasource event name to fix duplicate events on IBM's
Power10.
- Add PVN for HX-C2000 CPU with Power8 Architecture.
Intel:
- Alderlake/rocketlake metric fixes.
- Update emeraldrapids events to v1.02.
- Update icelakex events to v1.23.
- Update sapphirerapids events to v1.17.
- Add skx, clx, icx and spr upi bandwidth metric.
AMD:
- Add Zen 4 memory controller events.
RISC-V:
- Add StarFive Dubhe-80 and Dubhe-90 JSON files.
https://www.starfivetech.com/en/site/cpu-u
- Add T-HEAD C9xx JSON file.
https://github.com/riscv-software-src/opensbi/blob/master/docs/platform/thead-c9xx.md
ARM64:
- Remove UTF-8 characters from cmn.json, that were causing build
failure in some distros.
- Add core PMU events and metrics for Ampere One X.
- Rename Ampere One's BPU_FLUSH_MEM_FAULT to GPC_FLUSH_MEM_FAULT
libperf:
- Rename several perf_cpu_map constructor names to clarify what they
really do.
- Ditto for some other methods, coping with some issues in their
semantics, like perf_cpu_map__empty() ->
perf_cpu_map__has_any_cpu_or_is_empty().
- Document perf_cpu_map__nr()'s behavior
perf stat:
- Exit if parse groups fails.
- Combine the -A/--no-aggr and --no-merge options.
- Fix help message for --metric-no-threshold option.
Hardware tracing:
ARM64 CoreSight:
- Bump minimum OpenCSD version to ensure a bugfix is present.
- Add 'T' itrace option for timestamp trace
- Set start vm addr of exectable file to 0 and don't ignore first
sample on the arm-cs-trace-disasm.py 'perf script'"
* tag 'perf-tools-for-v6.8-1-2024-01-09' of git://git.kernel.org/pub/scm/linux/kernel/git/perf/perf-tools: (179 commits)
MAINTAINERS: Add Namhyung as tools/perf/ co-maintainer
perf test: test case 'Setup struct perf_event_attr' fails on s390 on z/vm
perf db-export: Fix missing reference count get in call_path_from_sample()
perf tests: Add perf script test
libsubcmd: Fix memory leak in uniq()
perf TUI: Don't ignore job control
perf vendor events intel: Update sapphirerapids events to v1.17
perf vendor events intel: Update icelakex events to v1.23
perf vendor events intel: Update emeraldrapids events to v1.02
perf vendor events intel: Alderlake/rocketlake metric fixes
perf x86 test: Add hybrid test for conflicting legacy/sysfs event
perf x86 test: Update hybrid expectations
perf vendor events amd: Add Zen 4 memory controller events
perf stat: Fix hard coded LL miss units
perf record: Reduce memory for recording PERF_RECORD_LOST_SAMPLES event
perf env: Avoid recursively taking env->bpf_progs.lock
perf annotate: Add --insn-stat option for debugging
perf annotate: Add --type-stat option for debugging
perf annotate: Support event group display
perf annotate: Add --data-type option
...
Diffstat (limited to 'tools/perf/Documentation')
-rw-r--r-- | tools/perf/Documentation/itrace.txt | 1 | ||||
-rw-r--r-- | tools/perf/Documentation/perf-annotate.txt | 11 | ||||
-rw-r--r-- | tools/perf/Documentation/perf-config.txt | 4 | ||||
-rw-r--r-- | tools/perf/Documentation/perf-list.txt | 12 | ||||
-rw-r--r-- | tools/perf/Documentation/perf-lock.txt | 2 | ||||
-rw-r--r-- | tools/perf/Documentation/perf-record.txt | 4 | ||||
-rw-r--r-- | tools/perf/Documentation/perf-report.txt | 3 | ||||
-rw-r--r-- | tools/perf/Documentation/perf-stat.txt | 52 | ||||
-rw-r--r-- | tools/perf/Documentation/perf.txt | 3 |
9 files changed, 60 insertions, 32 deletions
diff --git a/tools/perf/Documentation/itrace.txt b/tools/perf/Documentation/itrace.txt index a97f95825b14..19cc179be9a7 100644 --- a/tools/perf/Documentation/itrace.txt +++ b/tools/perf/Documentation/itrace.txt @@ -25,6 +25,7 @@ q quicker (less detailed) decoding A approximate IPC Z prefer to ignore timestamps (so-called "timeless" decoding) + T use the timestamp trace as kernel time The default is all events i.e. the same as --itrace=iybxwpe, except for perf script where it is --itrace=ce diff --git a/tools/perf/Documentation/perf-annotate.txt b/tools/perf/Documentation/perf-annotate.txt index fe168e8165c8..b95524bea021 100644 --- a/tools/perf/Documentation/perf-annotate.txt +++ b/tools/perf/Documentation/perf-annotate.txt @@ -155,6 +155,17 @@ include::itrace.txt[] stdio or stdio2 (Default: 0). Note that this is about selection of functions to display, not about lines within the function. +--data-type[=TYPE_NAME]:: + Display data type annotation instead of code. It infers data type of + samples (if they are memory accessing instructions) using DWARF debug + information. It can take an optional argument of data type name. In + that case it'd show annotation for the type only, otherwise it'd show + all data types it finds. + +--type-stat:: + Show stats for the data type annotation. + + SEE ALSO -------- linkperf:perf-record[1], linkperf:perf-report[1] diff --git a/tools/perf/Documentation/perf-config.txt b/tools/perf/Documentation/perf-config.txt index 0b4e79dbd3f6..379f9d7a8ab1 100644 --- a/tools/perf/Documentation/perf-config.txt +++ b/tools/perf/Documentation/perf-config.txt @@ -251,7 +251,8 @@ annotate.*:: addr2line binary to use for file names and line numbers. annotate.objdump:: - objdump binary to use for disassembly and annotations. + objdump binary to use for disassembly and annotations, + including in the 'perf test' command. annotate.disassembler_style:: Use this to change the default disassembler style to some other value @@ -722,7 +723,6 @@ session-<NAME>.*:: Defines new record session for daemon. The value is record's command line without the 'record' keyword. - SEE ALSO -------- linkperf:perf[1] diff --git a/tools/perf/Documentation/perf-list.txt b/tools/perf/Documentation/perf-list.txt index d5f78e125efe..1b90575ee3c8 100644 --- a/tools/perf/Documentation/perf-list.txt +++ b/tools/perf/Documentation/perf-list.txt @@ -81,11 +81,13 @@ For Intel systems precise event sampling is implemented with PEBS which supports up to precise-level 2, and precise level 3 for some special cases -On AMD systems it is implemented using IBS (up to precise-level 2). -The precise modifier works with event types 0x76 (cpu-cycles, CPU -clocks not halted) and 0xC1 (micro-ops retired). Both events map to -IBS execution sampling (IBS op) with the IBS Op Counter Control bit -(IbsOpCntCtl) set respectively (see the +On AMD systems it is implemented using IBS OP (up to precise-level 2). +Unlike Intel PEBS which provides levels of precision, AMD core pmu is +inherently non-precise and IBS is inherently precise. (i.e. ibs_op//, +ibs_op//p, ibs_op//pp and ibs_op//ppp are all same). The precise modifier +works with event types 0x76 (cpu-cycles, CPU clocks not halted) and 0xC1 +(micro-ops retired). Both events map to IBS execution sampling (IBS op) +with the IBS Op Counter Control bit (IbsOpCntCtl) set respectively (see the Core Complex (CCX) -> Processor x86 Core -> Instruction Based Sampling (IBS) section of the [AMD Processor Programming Reference (PPR)] relevant to the family, model and stepping of the processor being used). diff --git a/tools/perf/Documentation/perf-lock.txt b/tools/perf/Documentation/perf-lock.txt index 503abcba1438..f5938d616d75 100644 --- a/tools/perf/Documentation/perf-lock.txt +++ b/tools/perf/Documentation/perf-lock.txt @@ -119,7 +119,7 @@ INFO OPTIONS CONTENTION OPTIONS --------------- +------------------ -k:: --key=<value>:: diff --git a/tools/perf/Documentation/perf-record.txt b/tools/perf/Documentation/perf-record.txt index 1889f66addf2..6015fdd08fb6 100644 --- a/tools/perf/Documentation/perf-record.txt +++ b/tools/perf/Documentation/perf-record.txt @@ -445,6 +445,10 @@ following filters are defined: 4th-Gen Xeon+ server), the save branch type is unconditionally enabled when the taken branch stack sampling is enabled. - priv: save privilege state during sampling in case binary is not available later + - counter: save occurrences of the event since the last branch entry. Currently, the + feature is only supported by a newer CPU, e.g., Intel Sierra Forest and + later platforms. An error out is expected if it's used on the unsupported + kernel or CPUs. + The option requires at least one branch type among any, any_call, any_ret, ind_call, cond. diff --git a/tools/perf/Documentation/perf-report.txt b/tools/perf/Documentation/perf-report.txt index af068b4f1e5a..38f59ac064f7 100644 --- a/tools/perf/Documentation/perf-report.txt +++ b/tools/perf/Documentation/perf-report.txt @@ -118,6 +118,9 @@ OPTIONS - retire_lat: On X86, this reports pipeline stall of this instruction compared to the previous instruction in cycles. And currently supported only on X86 - simd: Flags describing a SIMD operation. "e" for empty Arm SVE predicate. "p" for partial Arm SVE predicate + - type: Data type of sample memory access. + - typeoff: Offset in the data type of sample memory access. + - symoff: Offset in the symbol. By default, comm, dso and symbol keys are used. (i.e. --sort comm,dso,symbol) diff --git a/tools/perf/Documentation/perf-stat.txt b/tools/perf/Documentation/perf-stat.txt index 8f789fa1242e..5af2e432b54f 100644 --- a/tools/perf/Documentation/perf-stat.txt +++ b/tools/perf/Documentation/perf-stat.txt @@ -422,7 +422,34 @@ See perf list output for the possible metrics and metricgroups. -A:: --no-aggr:: -Do not aggregate counts across all monitored CPUs. +--no-merge:: +Do not aggregate/merge counts across monitored CPUs or PMUs. + +When multiple events are created from a single event specification, +stat will, by default, aggregate the event counts and show the result +in a single row. This option disables that behavior and shows the +individual events and counts. + +Multiple events are created from a single event specification when: + +1. PID monitoring isn't requested and the system has more than one + CPU. For example, a system with 8 SMT threads will have one event + opened on each thread and aggregation is performed across them. + +2. Prefix or glob wildcard matching is used for the PMU name. For + example, multiple memory controller PMUs may exist typically with a + suffix of _0, _1, etc. By default the event counts will all be + combined if the PMU is specified without the suffix such as + uncore_imc rather than uncore_imc_0. + +3. Aliases, which are listed immediately after the Kernel PMU events + by perf list, are used. + +--hybrid-merge:: +Merge core event counts from all core PMUs. In hybrid or big.LITTLE +systems by default each core PMU will report its count +separately. This option forces core PMU counts to be combined to give +a behavior closer to having a single CPU type in the system. --topdown:: Print top-down metrics supported by the CPU. This allows to determine @@ -475,29 +502,6 @@ highlight 'tma_frontend_bound'. This metric may be drilled into with Error out if the input is higher than the supported max level. ---no-merge:: -Do not merge results from same PMUs. - -When multiple events are created from a single event specification, -stat will, by default, aggregate the event counts and show the result -in a single row. This option disables that behavior and shows -the individual events and counts. - -Multiple events are created from a single event specification when: -1. Prefix or glob matching is used for the PMU name. -2. Aliases, which are listed immediately after the Kernel PMU events - by perf list, are used. - ---hybrid-merge:: -Merge the hybrid event counts from all PMUs. - -For hybrid events, by default, the stat aggregates and reports the event -counts per PMU. But sometimes, it's also useful to aggregate event counts -from all PMUs. This option enables that behavior and reports the counts -without PMUs. - -For non-hybrid events, it should be no effect. - --smi-cost:: Measure SMI cost if msr/aperf/ and msr/smi/ events are supported. diff --git a/tools/perf/Documentation/perf.txt b/tools/perf/Documentation/perf.txt index ba3df49c169d..a7cf7bc2f968 100644 --- a/tools/perf/Documentation/perf.txt +++ b/tools/perf/Documentation/perf.txt @@ -64,6 +64,9 @@ OPTIONS perf-event-open - Print perf_event_open() arguments and return value +--debug-file:: + Write debug output to a specified file. + DESCRIPTION ----------- Performance counters for Linux are a new kernel-based subsystem |