The CAPIO daemon (server)

The CAPIO server component is reposnible for implementic the semantics of the CAPIO-CL coordination, as well as handling storage and communication between different nodes.

Parameters of the CAPIO server

For a list of all the parameter that the CAPIO server component supports, it is possible to execute capio_server --help. The most important flag is the -c (equivalent to --config) flag, which allows to tell the location of the CAPIO-CL configuration server.

Another important flag is the -b (--backend) flag which is used to specify the communication abckend between servers. At the moment, two backends are available: mpi(default) and mpisync (a more performant version of the mpi backend which is more heavy on cpu). Other backend might be developed in the future, but for this refer to th middleware built in help.

Control the behaviour of the CAPIO server component

Apart from the program arguments, the CAPIO server can be controlled trough some environment variables:

  • CAPIO_DIR This environment variable tells to both server and posix intercept library the mount point of capio, that is the folder in which capio will perform interception;
  • CAPIO_LOG_LEVEL this environment tells both server and application the log level to use. This variable works only if -DCAPIO_LOG=TRUE was specified during cmake phase;
  • CAPIO_LOG_PREFIX This environment variable is defined only for capio_posix applications and specifies the prefix of the logfile name to which capio will log to. The default value is posix_thread_, which means that capio will log by default to a set of files called posix_thread_*.log. An equivalent behaviour can be set on the capio server using the -l option;
  • CAPIO_LOG_DIR This environment variable is defined only for capio_posix applications and specifies the directory name to which capio will be created. If this variable is not defined, capio will log by default to capio_logs. An equivalent behaviour can be set on the capio server using the -d option;
  • CAPIO_CACHE_LINES: This environment variable controls how many lines of cache are presents between posix and server applications. defaults to 10 lines;

  • CAPIO_CACHE_LINE_SIZE: This environment variable controls the size of a single cache line. defaults to 256KB;

  • CAPIO_FILE_INIT_SIZE: This environment variable defines the default size of pre allocated memory for a new file handled by capio. Defaults to 4MB. Bigger sizes will reduce the overhead of malloc but will fill faster node memory. Value has to be expressed in bytes;

  • CAPIO_PREFETCH_DATA_SIZE: If this variable is set, then data transfers between nodes will be always, at least of the given value in bytes;