1perf-c2c(1)
2===========
3
4NAME
5----
6perf-c2c - Shared Data C2C/HITM Analyzer.
7
8SYNOPSIS
9--------
10[verse]
11'perf c2c record' [<options>] <command>
12'perf c2c record' [<options>] -- [<record command options>] <command>
13'perf c2c report' [<options>]
14
15DESCRIPTION
16-----------
17C2C stands for Cache To Cache.
18
19The perf c2c tool provides means for Shared Data C2C/HITM analysis. It allows
20you to track down the cacheline contentions.
21
22The tool is based on x86's load latency and precise store facility events
23provided by Intel CPUs. These events provide:
24  - memory address of the access
25  - type of the access (load and store details)
26  - latency (in cycles) of the load access
27
28The c2c tool provide means to record this data and report back access details
29for cachelines with highest contention - highest number of HITM accesses.
30
31The basic workflow with this tool follows the standard record/report phase.
32User uses the record command to record events data and report command to
33display it.
34
35
36RECORD OPTIONS
37--------------
38-e::
39--event=::
40	Select the PMU event. Use 'perf mem record -e list'
41	to list available events.
42
43-v::
44--verbose::
45	Be more verbose (show counter open errors, etc).
46
47-l::
48--ldlat::
49	Configure mem-loads latency.
50
51-k::
52--all-kernel::
53	Configure all used events to run in kernel space.
54
55-u::
56--all-user::
57	Configure all used events to run in user space.
58
59REPORT OPTIONS
60--------------
61-k::
62--vmlinux=<file>::
63	vmlinux pathname
64
65-v::
66--verbose::
67	Be more verbose (show counter open errors, etc).
68
69-i::
70--input::
71	Specify the input file to process.
72
73-N::
74--node-info::
75	Show extra node info in report (see NODE INFO section)
76
77-c::
78--coalesce::
79	Specify sorting fields for single cacheline display.
80	Following fields are available: tid,pid,iaddr,dso
81	(see COALESCE)
82
83-g::
84--call-graph::
85	Setup callchains parameters.
86	Please refer to perf-report man page for details.
87
88--stdio::
89	Force the stdio output (see STDIO OUTPUT)
90
91--stats::
92	Display only statistic tables and force stdio mode.
93
94--full-symbols::
95	Display full length of symbols.
96
97--no-source::
98	Do not display Source:Line column.
99
100--show-all::
101	Show all captured HITM lines, with no regard to HITM % 0.0005 limit.
102
103-f::
104--force::
105	Don't do ownership validation.
106
107-d::
108--display::
109	Switch to HITM type (rmt, lcl) to display and sort on. Total HITMs as default.
110
111C2C RECORD
112----------
113The perf c2c record command setup options related to HITM cacheline analysis
114and calls standard perf record command.
115
116Following perf record options are configured by default:
117(check perf record man page for details)
118
119  -W,-d,--phys-data,--sample-cpu
120
121Unless specified otherwise with '-e' option, following events are monitored by
122default:
123
124  cpu/mem-loads,ldlat=30/P
125  cpu/mem-stores/P
126
127User can pass any 'perf record' option behind '--' mark, like (to enable
128callchains and system wide monitoring):
129
130  $ perf c2c record -- -g -a
131
132Please check RECORD OPTIONS section for specific c2c record options.
133
134C2C REPORT
135----------
136The perf c2c report command displays shared data analysis.  It comes in two
137display modes: stdio and tui (default).
138
139The report command workflow is following:
140  - sort all the data based on the cacheline address
141  - store access details for each cacheline
142  - sort all cachelines based on user settings
143  - display data
144
145In general perf report output consist of 2 basic views:
146  1) most expensive cachelines list
147  2) offsets details for each cacheline
148
149For each cacheline in the 1) list we display following data:
150(Both stdio and TUI modes follow the same fields output)
151
152  Index
153  - zero based index to identify the cacheline
154
155  Cacheline
156  - cacheline address (hex number)
157
158  Total records
159  - sum of all cachelines accesses
160
161  Rmt/Lcl Hitm
162  - cacheline percentage of all Remote/Local HITM accesses
163
164  LLC Load Hitm - Total, Lcl, Rmt
165  - count of Total/Local/Remote load HITMs
166
167  Store Reference - Total, L1Hit, L1Miss
168    Total - all store accesses
169    L1Hit - store accesses that hit L1
170    L1Hit - store accesses that missed L1
171
172  Load Dram
173  - count of local and remote DRAM accesses
174
175  LLC Ld Miss
176  - count of all accesses that missed LLC
177
178  Total Loads
179  - sum of all load accesses
180
181  Core Load Hit - FB, L1, L2
182  - count of load hits in FB (Fill Buffer), L1 and L2 cache
183
184  LLC Load Hit - Llc, Rmt
185  - count of LLC and Remote load hits
186
187For each offset in the 2) list we display following data:
188
189  HITM - Rmt, Lcl
190  - % of Remote/Local HITM accesses for given offset within cacheline
191
192  Store Refs - L1 Hit, L1 Miss
193  - % of store accesses that hit/missed L1 for given offset within cacheline
194
195  Data address - Offset
196  - offset address
197
198  Pid
199  - pid of the process responsible for the accesses
200
201  Tid
202  - tid of the process responsible for the accesses
203
204  Code address
205  - code address responsible for the accesses
206
207  cycles - rmt hitm, lcl hitm, load
208    - sum of cycles for given accesses - Remote/Local HITM and generic load
209
210  cpu cnt
211    - number of cpus that participated on the access
212
213  Symbol
214    - code symbol related to the 'Code address' value
215
216  Shared Object
217    - shared object name related to the 'Code address' value
218
219  Source:Line
220    - source information related to the 'Code address' value
221
222  Node
223    - nodes participating on the access (see NODE INFO section)
224
225NODE INFO
226---------
227The 'Node' field displays nodes that accesses given cacheline
228offset. Its output comes in 3 flavors:
229  - node IDs separated by ','
230  - node IDs with stats for each ID, in following format:
231      Node{cpus %hitms %stores}
232  - node IDs with list of affected CPUs in following format:
233      Node{cpu list}
234
235User can switch between above flavors with -N option or
236use 'n' key to interactively switch in TUI mode.
237
238COALESCE
239--------
240User can specify how to sort offsets for cacheline.
241
242Following fields are available and governs the final
243output fields set for caheline offsets output:
244
245  tid   - coalesced by process TIDs
246  pid   - coalesced by process PIDs
247  iaddr - coalesced by code address, following fields are displayed:
248             Code address, Code symbol, Shared Object, Source line
249  dso   - coalesced by shared object
250
251By default the coalescing is setup with 'pid,iaddr'.
252
253STDIO OUTPUT
254------------
255The stdio output displays data on standard output.
256
257Following tables are displayed:
258  Trace Event Information
259  - overall statistics of memory accesses
260
261  Global Shared Cache Line Event Information
262  - overall statistics on shared cachelines
263
264  Shared Data Cache Line Table
265  - list of most expensive cachelines
266
267  Shared Cache Line Distribution Pareto
268  - list of all accessed offsets for each cacheline
269
270TUI OUTPUT
271----------
272The TUI output provides interactive interface to navigate
273through cachelines list and to display offset details.
274
275For details please refer to the help window by pressing '?' key.
276
277CREDITS
278-------
279Although Don Zickus, Dick Fowles and Joe Mario worked together
280to get this implemented, we got lots of early help from Arnaldo
281Carvalho de Melo, Stephane Eranian, Jiri Olsa and Andi Kleen.
282
283C2C BLOG
284--------
285Check Joe's blog on c2c tool for detailed use case explanation:
286  https://joemario.github.io/blog/2016/09/01/c2c-blog/
287
288SEE ALSO
289--------
290linkperf:perf-record[1], linkperf:perf-mem[1]
291