1erts_alloc_config(3) Erlang Module Definition erts_alloc_config(3)
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6 erts_alloc_config - Configuration tool for erts_alloc
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9 Warning:
10 This (experimental) tool no longer produces good configurations and
11 cannot be fixed in a reasonably backwards compatible manner. It has
12 therefore been scheduled for removal in OTP 26.0.
13 erts_alloc(3) is an Erlang Run-Time System internal memory allocator
16 library. erts_alloc_config is intended to be used to aid creation of an
17 erts_alloc(3) configuration that is suitable for a limited number of
18 runtime scenarios. The configuration that erts_alloc_config produce is
19 intended as a suggestion, and may need to be adjusted manually.
20 The configuration is created based on information about a number of
22 runtime scenarios. It is obviously impossible to foresee every runtime
23 scenario that can occur. The important scenarios are those that cause
24 maximum or minimum load on specific memory allocators. Load in this
25 context is total size of memory blocks allocated.
26 The current implementation of erts_alloc_config concentrate on configu‐
28 ration of multi-block carriers. Information gathered when a runtime
29 scenario is saved is mainly current and maximum use of multi-block car‐
30 riers. If a parameter that change the use of multi-block carriers is
31 changed, a previously generated configuration is invalid and erts_al‐
32 loc_config needs to be run again. It is mainly the single block carrier
33 threshold that effects the use of multi-block carriers, but other sin‐
34 gle-block carrier parameters might as well. If another value of a sin‐
35 gle block carrier parameter than the default is desired, use the de‐
36 sired value when running erts_alloc_config.
37 A configuration is created in the following way:
39 * Pass the +Mea config command-line flag to the Erlang runtime system
41 you are going to use for creation of the allocator configuration.
42 It will disable features that prevent erts_alloc_config from doing
43 its job. Note, you should not use this flag when using the created
44 configuration. Also note that it is important that you use the same
45 amount of schedulers when creating the configuration as you are go‐
46 ing the use on the system using the configuration.
47 * Run your applications with different scenarios (the more the bet‐
49 ter) and save information about each scenario by calling save_sce‐
50 nario/0. It may be hard to know when the applications are at an
51 (for erts_alloc_config) important runtime scenario. A good approach
52 may therefore be to call save_scenario/0 repeatedly, e.g. once ev‐
53 ery tenth second. Note that it is important that your applications
54 reach the runtime scenarios that are important for erts_alloc_con‐
55 fig when you are saving scenarios; otherwise, the configuration may
56 perform bad.
57 * When you have covered all scenarios, call make_config/1 in order to
59 create a configuration. The configuration is written to a file that
60 you have chosen. This configuration file can later be read by an
61 Erlang runtime-system at startup. Pass the command line argument
62 -args_file FileName to the erl(1) command.
63 * The configuration produced by erts_alloc_config may need to be man‐
65 ually adjusted as already stated. Do not modify the file produced
66 by erts_alloc_config; instead, put your modifications in another
67 file and load this file after the file produced by erts_alloc_con‐
68 fig. That is, put the -args_file FileName argument that reads your
69 modification file later on the command-line than the -args_file
70 FileName argument that reads the configuration file produced by
71 erts_alloc_config. If a memory allocation parameter appear multiple
72 times, the last version of will be used, i.e., you can override pa‐
73 rameters in the configuration file produced by erts_alloc_config.
74 Doing it this way simplifies things when you want to rerun erts_al‐
75 loc_config.
76 Note:
78 The configuration created by erts_alloc_config may perform bad, ever
79 horrible, for runtime scenarios that are very different from the ones
80 saved when creating the configuration. You are, therefore, advised to
81 rerun erts_alloc_config if the applications run when the configuration
82 was made are changed, or if the load on the applications have changed
83 since the configuration was made. You are also advised to rerun
84 erts_alloc_config if the Erlang runtime system used is changed.
85 erts_alloc_config saves information about runtime scenarios and per‐
88 forms computations in a server that is automatically started. The
89 server register itself under the name '__erts_alloc_config__'.
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92 save_scenario() -> ok | {error, Error}
93 Types:
95 Error = term()
97 save_scenario/0 saves information about the current runtime sce‐
99 nario. This information will later be used when make_config/0,
100 or make_config/1 is called.
101 The first time save_scenario/0 is called a server will be
103 started. This server will save runtime scenarios. All saved sce‐
104 narios can be removed by calling stop/0.
105 make_config() -> ok | {error, Error}
107 Types:
109 Error = term()
111 This is the same as calling make_config(group_leader()).
113 make_config(FileNameOrIODev) -> ok | {error, Error}
115 Types:
117 FileNameOrIODev = string() | io_device()
119 Error = term()
120 make_config/1 uses the information previously saved by save_sce‐
122 nario/0 in order to produce an erts_alloc configuration. At
123 least one scenario have had to be saved. All scenarios previ‐
124 ously saved will be used when creating the configuration.
125 If FileNameOrIODev is a string(), make_config/1 will use File‐
127 NameOrIODev as a filename. A file named FileNameOrIODev is cre‐
128 ated and the configuration will be written to that file. If
129 FileNameOrIODev is an io_device() (see the documentation of the
130 module io), the configuration will be written to the io device.
131 stop() -> ok | {error, Error}
133 Types:
135 Error = term()
137 Stops the server that saves runtime scenarios.
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141 erts_alloc(3), erl(1), io(3)
142Ericsson AB runtime_tools 1.19 erts_alloc_config(3)