perf-list (1)
Leading comments
Title: perf-list
Author: [FIXME: author] [see http://docbook.sf.net/el/author]
Generator: DocBook XSL Stylesheets v1.79.1 <http://docbook.sf.net/>
Date: 09/12/2017
Manual: perf Manual
Source: perf
Language: English
NAME
perf-list - List all symbolic event typesSYNOPSIS
perf list [--no-desc] [--long-desc] [hw|sw|cache|tracepoint|pmu|sdt|event_glob]
DESCRIPTION
This command displays the symbolic event types which can be selected in the various perf commands with the -e option.
OPTIONS
--no-desc
- Doncqt print descriptions.
-v, --long-desc
- Print longer event descriptions.
--details
- Print how named events are resolved internally into perf events, and also any extra expressions computed by perf stat.
EVENT MODIFIERS
Events can optionally have a modifier by appending a colon and one or more modifiers. Modifiers allow the user to restrict the events to be counted. The following modifiers exist:
-
u - user-space counting k - kernel counting h - hypervisor counting I - non idle counting G - guest counting (in KVM guests) H - host counting (not in KVM guests) p - precise level P - use maximum detected precise level S - read sample value (PERF_SAMPLE_READ) D - pin the event to the PMU
The p modifier can be used for specifying how precise the instruction address should be. The p modifier can be specified multiple times:
-
0 - SAMPLE_IP can have arbitrary skid 1 - SAMPLE_IP must have constant skid 2 - SAMPLE_IP requested to have 0 skid 3 - SAMPLE_IP must have 0 skid, or uses randomization to avoid sample shadowing effects.
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 AMD64 Architecture Programmercqs Manual Volume 2: System Programming, 13.3 Instruction-Based Sampling). Examples to use IBS:
-
perf record -a -e cpu-cycles:p ... # use ibs op counting cycles perf record -a -e r076:p ... # same as -e cpu-cycles:p perf record -a -e r0C1:p ... # use ibs op counting micro-ops
RAW HARDWARE EVENT DESCRIPTOR
Even when an event is not available in a symbolic form within perf right now, it can be encoded in a per processor specific way.
For instance For x86 CPUs NNN represents the raw register encoding with the layout of IA32_PERFEVTSELx MSRs (see [Intel® 64 and IA-32 Architectures Software Developercqs Manual Volume 3B: System Programming Guide] Figure 30-1 Layout of IA32_PERFEVTSELx MSRs) or AMDcqs PerfEvtSeln (see [AMD64 Architecture Programmercqs Manual Volume 2: System Programming], Page 344, Figure 13-7 Performance Event-Select Register (PerfEvtSeln)).
Note: Only the following bit fields can be set in x86 counter registers: event, umask, edge, inv, cmask. Esp. guest/host only and OS/user mode flags must be setup using EVENT MODIFIERS.
Example:
If the Intel docs for a QM720 Core i7 describe an event as:
-
Event Umask Event Mask Num. Value Mnemonic Description Comment
-
A8H 01H LSD.UOPS Counts the number of micro-ops Use cmask=1 and delivered by loop stream detector invert to count cycles
raw encoding of 0x1A8 can be used:
-
perf stat -e r1a8 -a sleep 1 perf record -e r1a8 ...
You should refer to the processor specific documentation for getting these details. Some of them are referenced in the SEE ALSO section below.
ARBITRARY PMUS
perf also supports an extended syntax for specifying raw parameters to PMUs. Using this typically requires looking up the specific event in the CPU vendor specific documentation.
The available PMUs and their raw parameters can be listed with
-
ls /sys/devices/*/format
For example the raw event "LSD.UOPS" core pmu event above could be specified as
-
perf stat -e cpu/event=0xa8,umask=0x1,name=LSD.UOPS_CYCLES,cmask=1/ ...
PER SOCKET PMUS
Some PMUs are not associated with a core, but with a whole CPU socket. Events on these PMUs generally cannot be sampled, but only counted globally with perf stat -a. They can be bound to one logical CPU, but will measure all the CPUs in the same socket.
This example measures memory bandwidth every second on the first memory controller on socket 0 of a Intel Xeon system
-
perf stat -C 0 -a uncore_imc_0/cas_count_read/,uncore_imc_0/cas_count_write/ -I 1000 ...
Each memory controller has its own PMU. Measuring the complete system bandwidth would require specifying all imc PMUs (see perf list output), and adding the values together.
This example measures the combined core power every second
-
perf stat -I 1000 -e power/energy-cores/ -a
ACCESS RESTRICTIONS
For non root users generally only context switched PMU events are available. This is normally only the events in the cpu PMU, the predefined events like cycles and instructions and some software events.
Other PMUs and global measurements are normally root only. Some event qualifiers, such as "any", are also root only.
This can be overriden by setting the kernel.perf_event_paranoid sysctl to -1, which allows non root to use these events.
For accessing trace point events perf needs to have read access to /sys/kernel/debug/tracing, even when perf_event_paranoid is in a relaxed setting.
TRACING
Some PMUs control advanced hardware tracing capabilities, such as Intel PT, that allows low overhead execution tracing. These are described in a separate intel-pt.txt document.
PARAMETERIZED EVENTS
Some pmu events listed by perf-list will be displayed with ? in them. For example:
-
hv_gpci/dtbp_ptitc,phys_processor_idx=?/
This means that when provided as an event, a value for ? must also be supplied. For example:
-
perf stat -C 0 -e 'hv_gpci/dtbp_ptitc,phys_processor_idx=0x2/' ...
EVENT GROUPS
Perf supports time based multiplexing of events, when the number of events active exceeds the number of hardware performance counters. Multiplexing can cause measurement errors when the workload changes its execution profile.
When metrics are computed using formulas from event counts, it is useful to ensure some events are always measured together as a group to minimize multiplexing errors. Event groups can be specified using { }.
-
perf stat -e '{instructions,cycles}' ...
The number of available performance counters depend on the CPU. A group cannot contain more events than available counters. For example Intel Core CPUs typically have four generic performance counters for the core, plus three fixed counters for instructions, cycles and ref-cycles. Some special events have restrictions on which counter they can schedule, and may not support multiple instances in a single group. When too many events are specified in the group none of them will not be measured.
Globally pinned events can limit the number of counters available for other groups. On x86 systems, the NMI watchdog pins a counter by default. The nmi watchdog can be disabled as root with
-
echo 0 > /proc/sys/kernel/nmi_watchdog
Events from multiple different PMUs cannot be mixed in a group, with some exceptions for software events.
LEADER SAMPLING
perf also supports group leader sampling using the :S specifier.
-
perf record -e '{cycles,instructions}:S' ... perf report --group
Normally all events in a event group sample, but with :S only the first event (the leader) samples, and it only reads the values of the other events in the group.
OPTIONS
Without options all known events will be listed.
To limit the list use:
- 1. hw or hardware to list hardware events such as cache-misses, etc.
- 2. sw or software to list software events such as context switches, etc.
- 3. cache or hwcache to list hardware cache events such as L1-dcache-loads, etc.
- 4. tracepoint to list all tracepoint events, alternatively use subsys_glob:event_glob to filter by tracepoint subsystems such as sched, block, etc.
- 5. pmu to print the kernel supplied PMU events.
- 6. sdt to list all Statically Defined Tracepoint events.
- 7. If none of the above is matched, it will apply the supplied glob to all events, printing the ones that match.
- 8. As a last resort, it will do a substring search in all event names.
One or more types can be used at the same time, listing the events for the types specified.
Support raw format:
- 1. --raw-dump, shows the raw-dump of all the events.
- 2. --raw-dump [hw|sw|cache|tracepoint|pmu|event_glob], shows the raw-dump of a certain kind of events.
SEE ALSO
perf-stat(1), perf-top(1), perf-record(1), m[blue]Intel® 64 and IA-32 Architectures Software Developercqs Manual Volume 3B: System Programming Guidem[]
NOTES
- 1.
- Intel® 64 and IA-32 Architectures Software Developercqs Manual Volume 3B: System Programming Guide
- 2.
-
AMD64 Architecture Programmercqs Manual Volume 2: System Programming