312 lines
7.9 KiB
Plaintext
312 lines
7.9 KiB
Plaintext
perf-c2c(1)
|
|
===========
|
|
|
|
NAME
|
|
----
|
|
perf-c2c - Shared Data C2C/HITM Analyzer.
|
|
|
|
SYNOPSIS
|
|
--------
|
|
[verse]
|
|
'perf c2c record' [<options>] <command>
|
|
'perf c2c record' [<options>] \-- [<record command options>] <command>
|
|
'perf c2c report' [<options>]
|
|
|
|
DESCRIPTION
|
|
-----------
|
|
C2C stands for Cache To Cache.
|
|
|
|
The perf c2c tool provides means for Shared Data C2C/HITM analysis. It allows
|
|
you to track down the cacheline contentions.
|
|
|
|
On x86, the tool is based on load latency and precise store facility events
|
|
provided by Intel CPUs. On PowerPC, the tool uses random instruction sampling
|
|
with thresholding feature.
|
|
|
|
These events provide:
|
|
- memory address of the access
|
|
- type of the access (load and store details)
|
|
- latency (in cycles) of the load access
|
|
|
|
The c2c tool provide means to record this data and report back access details
|
|
for cachelines with highest contention - highest number of HITM accesses.
|
|
|
|
The basic workflow with this tool follows the standard record/report phase.
|
|
User uses the record command to record events data and report command to
|
|
display it.
|
|
|
|
|
|
RECORD OPTIONS
|
|
--------------
|
|
-e::
|
|
--event=::
|
|
Select the PMU event. Use 'perf c2c record -e list'
|
|
to list available events.
|
|
|
|
-v::
|
|
--verbose::
|
|
Be more verbose (show counter open errors, etc).
|
|
|
|
-l::
|
|
--ldlat::
|
|
Configure mem-loads latency. (x86 only)
|
|
|
|
-k::
|
|
--all-kernel::
|
|
Configure all used events to run in kernel space.
|
|
|
|
-u::
|
|
--all-user::
|
|
Configure all used events to run in user space.
|
|
|
|
REPORT OPTIONS
|
|
--------------
|
|
-k::
|
|
--vmlinux=<file>::
|
|
vmlinux pathname
|
|
|
|
-v::
|
|
--verbose::
|
|
Be more verbose (show counter open errors, etc).
|
|
|
|
-i::
|
|
--input::
|
|
Specify the input file to process.
|
|
|
|
-N::
|
|
--node-info::
|
|
Show extra node info in report (see NODE INFO section)
|
|
|
|
-c::
|
|
--coalesce::
|
|
Specify sorting fields for single cacheline display.
|
|
Following fields are available: tid,pid,iaddr,dso
|
|
(see COALESCE)
|
|
|
|
-g::
|
|
--call-graph::
|
|
Setup callchains parameters.
|
|
Please refer to perf-report man page for details.
|
|
|
|
--stdio::
|
|
Force the stdio output (see STDIO OUTPUT)
|
|
|
|
--stats::
|
|
Display only statistic tables and force stdio mode.
|
|
|
|
--full-symbols::
|
|
Display full length of symbols.
|
|
|
|
--no-source::
|
|
Do not display Source:Line column.
|
|
|
|
--show-all::
|
|
Show all captured HITM lines, with no regard to HITM % 0.0005 limit.
|
|
|
|
-f::
|
|
--force::
|
|
Don't do ownership validation.
|
|
|
|
-d::
|
|
--display::
|
|
Switch to HITM type (rmt, lcl) to display and sort on. Total HITMs as default.
|
|
|
|
--stitch-lbr::
|
|
Show callgraph with stitched LBRs, which may have more complete
|
|
callgraph. The perf.data file must have been obtained using
|
|
perf c2c record --call-graph lbr.
|
|
Disabled by default. In common cases with call stack overflows,
|
|
it can recreate better call stacks than the default lbr call stack
|
|
output. But this approach is not full proof. There can be cases
|
|
where it creates incorrect call stacks from incorrect matches.
|
|
The known limitations include exception handing such as
|
|
setjmp/longjmp will have calls/returns not match.
|
|
|
|
C2C RECORD
|
|
----------
|
|
The perf c2c record command setup options related to HITM cacheline analysis
|
|
and calls standard perf record command.
|
|
|
|
Following perf record options are configured by default:
|
|
(check perf record man page for details)
|
|
|
|
-W,-d,--phys-data,--sample-cpu
|
|
|
|
Unless specified otherwise with '-e' option, following events are monitored by
|
|
default on x86:
|
|
|
|
cpu/mem-loads,ldlat=30/P
|
|
cpu/mem-stores/P
|
|
|
|
and following on PowerPC:
|
|
|
|
cpu/mem-loads/
|
|
cpu/mem-stores/
|
|
|
|
User can pass any 'perf record' option behind '--' mark, like (to enable
|
|
callchains and system wide monitoring):
|
|
|
|
$ perf c2c record -- -g -a
|
|
|
|
Please check RECORD OPTIONS section for specific c2c record options.
|
|
|
|
C2C REPORT
|
|
----------
|
|
The perf c2c report command displays shared data analysis. It comes in two
|
|
display modes: stdio and tui (default).
|
|
|
|
The report command workflow is following:
|
|
- sort all the data based on the cacheline address
|
|
- store access details for each cacheline
|
|
- sort all cachelines based on user settings
|
|
- display data
|
|
|
|
In general perf report output consist of 2 basic views:
|
|
1) most expensive cachelines list
|
|
2) offsets details for each cacheline
|
|
|
|
For each cacheline in the 1) list we display following data:
|
|
(Both stdio and TUI modes follow the same fields output)
|
|
|
|
Index
|
|
- zero based index to identify the cacheline
|
|
|
|
Cacheline
|
|
- cacheline address (hex number)
|
|
|
|
Rmt/Lcl Hitm
|
|
- cacheline percentage of all Remote/Local HITM accesses
|
|
|
|
LLC Load Hitm - Total, LclHitm, RmtHitm
|
|
- count of Total/Local/Remote load HITMs
|
|
|
|
Total records
|
|
- sum of all cachelines accesses
|
|
|
|
Total loads
|
|
- sum of all load accesses
|
|
|
|
Total stores
|
|
- sum of all store accesses
|
|
|
|
Store Reference - L1Hit, L1Miss
|
|
L1Hit - store accesses that hit L1
|
|
L1Miss - store accesses that missed L1
|
|
|
|
Core Load Hit - FB, L1, L2
|
|
- count of load hits in FB (Fill Buffer), L1 and L2 cache
|
|
|
|
LLC Load Hit - LlcHit, LclHitm
|
|
- count of LLC load accesses, includes LLC hits and LLC HITMs
|
|
|
|
RMT Load Hit - RmtHit, RmtHitm
|
|
- count of remote load accesses, includes remote hits and remote HITMs
|
|
|
|
Load Dram - Lcl, Rmt
|
|
- count of local and remote DRAM accesses
|
|
|
|
For each offset in the 2) list we display following data:
|
|
|
|
HITM - Rmt, Lcl
|
|
- % of Remote/Local HITM accesses for given offset within cacheline
|
|
|
|
Store Refs - L1 Hit, L1 Miss
|
|
- % of store accesses that hit/missed L1 for given offset within cacheline
|
|
|
|
Data address - Offset
|
|
- offset address
|
|
|
|
Pid
|
|
- pid of the process responsible for the accesses
|
|
|
|
Tid
|
|
- tid of the process responsible for the accesses
|
|
|
|
Code address
|
|
- code address responsible for the accesses
|
|
|
|
cycles - rmt hitm, lcl hitm, load
|
|
- sum of cycles for given accesses - Remote/Local HITM and generic load
|
|
|
|
cpu cnt
|
|
- number of cpus that participated on the access
|
|
|
|
Symbol
|
|
- code symbol related to the 'Code address' value
|
|
|
|
Shared Object
|
|
- shared object name related to the 'Code address' value
|
|
|
|
Source:Line
|
|
- source information related to the 'Code address' value
|
|
|
|
Node
|
|
- nodes participating on the access (see NODE INFO section)
|
|
|
|
NODE INFO
|
|
---------
|
|
The 'Node' field displays nodes that accesses given cacheline
|
|
offset. Its output comes in 3 flavors:
|
|
- node IDs separated by ','
|
|
- node IDs with stats for each ID, in following format:
|
|
Node{cpus %hitms %stores}
|
|
- node IDs with list of affected CPUs in following format:
|
|
Node{cpu list}
|
|
|
|
User can switch between above flavors with -N option or
|
|
use 'n' key to interactively switch in TUI mode.
|
|
|
|
COALESCE
|
|
--------
|
|
User can specify how to sort offsets for cacheline.
|
|
|
|
Following fields are available and governs the final
|
|
output fields set for cacheline offsets output:
|
|
|
|
tid - coalesced by process TIDs
|
|
pid - coalesced by process PIDs
|
|
iaddr - coalesced by code address, following fields are displayed:
|
|
Code address, Code symbol, Shared Object, Source line
|
|
dso - coalesced by shared object
|
|
|
|
By default the coalescing is setup with 'pid,iaddr'.
|
|
|
|
STDIO OUTPUT
|
|
------------
|
|
The stdio output displays data on standard output.
|
|
|
|
Following tables are displayed:
|
|
Trace Event Information
|
|
- overall statistics of memory accesses
|
|
|
|
Global Shared Cache Line Event Information
|
|
- overall statistics on shared cachelines
|
|
|
|
Shared Data Cache Line Table
|
|
- list of most expensive cachelines
|
|
|
|
Shared Cache Line Distribution Pareto
|
|
- list of all accessed offsets for each cacheline
|
|
|
|
TUI OUTPUT
|
|
----------
|
|
The TUI output provides interactive interface to navigate
|
|
through cachelines list and to display offset details.
|
|
|
|
For details please refer to the help window by pressing '?' key.
|
|
|
|
CREDITS
|
|
-------
|
|
Although Don Zickus, Dick Fowles and Joe Mario worked together
|
|
to get this implemented, we got lots of early help from Arnaldo
|
|
Carvalho de Melo, Stephane Eranian, Jiri Olsa and Andi Kleen.
|
|
|
|
C2C BLOG
|
|
--------
|
|
Check Joe's blog on c2c tool for detailed use case explanation:
|
|
https://joemario.github.io/blog/2016/09/01/c2c-blog/
|
|
|
|
SEE ALSO
|
|
--------
|
|
linkperf:perf-record[1], linkperf:perf-mem[1]
|