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erts_alloc(3) is an
Erlang Run-Time System internal memory allocator library.
erts_alloc_config
is intended to be used to aid creation
of an erts_alloc(3)
configuration that is suitable for a limited number of runtime
scenarios. The configuration that erts_alloc_config
produce is intended as a suggestion, and may need to be
adjusted manually.
The configuration is created based on information about a number of runtime scenarios. It is obviously impossible to forsee every runtime scenario that can occur. The important scenarios are those that cause maximum or minimum load on specific memory allocators. Load in this context is total size of memory blocks allocated.
The current implementation of erts_alloc_config
concentrate
on configuration of multi-block carriers. Information gathered
when a runtime scenario is saved is mainly current and maximum use
of multi-block carriers. If a parameter that change the use of
multi-block carriers is changed, a previously generated
configuration is invalid and erts_alloc_config
needs
to be run again. It is mainly the single block carrier threshold
that effects the use of multi-block carriers, but other
single-block carrier parameters might as well. If another value of
a single block carrier parameter than the default is desired, use
the desired value when running erts_alloc_config
.
A configuration is created in the following way:
erts_alloc_config
) important runtime scenario. A good
approach may therefore be to call
save_scenario/0
repeatedly, e.g. once every tenth second. Note that it is
important that your applications reach the runtime scenarios
that are important for erts_alloc_config
when you are
saving scenarios; otherwise, the configuration may perform
bad.
erts_alloc_config
may
need to be manually adjusted as already stated. Do not modify the
file produced by erts_alloc_config
; instead, put your
modifications in another file and load this file after the
file produced by erts_alloc_config
. That is, put the
-args_file FileName
argument that reads your modification file later on the
command-line than the
-args_file FileName
argument that reads the configuration file produced by
erts_alloc_config
. If a memory allocation parameter
appear multiple times, the last version of will be used, i.e.,
you can override parameters in the configuration file produced
by erts_alloc_config
. Doing it this way simplifies
things when you want to rerun erts_alloc_config
.
The configuration created by |
erts_alloc_config
saves information about runtime scenarios
and performs computations in a server that is automatically
started. The server register itself under the name
'__erts_alloc_config__'
.
save_scenario() -> ok | {error, Error}
Types:
Error = term()
save_scenario/0
saves information about the current
runtime scenario. This information will later be used when
make_config/0,
or make_config/1
is called.
The first time save_scenario/0
is called a server
will be started. This server will save runtime scenarios. All
saved scenarios can be removed by calling
stop/0.
make_config() -> ok | {error, Error}
Types:
Error = term()
This is the same as calling make_config(group_leader()).
make_config(FileNameOrIODev) -> ok | {error, Error}
Types:
FileNameOrIODev = string() | io_device()
Error = term()
make_config/1
uses the information previously saved by
save_scenario/0
in order to produce an erts_alloc
configuration. At
least one scenario have had to be saved. All scenarios
previously saved will be used when creating the
configuration.
If FileNameOrIODev
is a string()
,
make_config/1
will use FileNameOrIODev
as a
filename. A file named FileNameOrIODev
is created and
the configuration will be written to that file. If
FileNameOrIODev
is an
io_device() (see the
documentation of the module
io), the configuration
will be written to the io device.
Types:
Error = term()
Stops the server that saves runtime scenarios.