The POSIX intercepting library

To implement the CAPIO-CL semantics, an intercepting library has been created. This library need to be loaded between the gnu libc library and the application trough the LD_PRELOAD environmental variable.

Control the behaviour of libcapio_posix

To manage the behaviour of the POSIX intercepting library, several environmental variables are available, none of which are mandatory:

  • 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.
  • 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.
  • 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;

The following variables not mandatoy but should allways be set. If not provided to a posix, application, CAPIO will not be able to correctly handle the application, according to the specifications given from the json configuration file (as the default values will be applied)!

  • CAPIO_WORKFLOW_NAME: This environment variable is used to define the scope of a workflow for a given step. Needs to be the same one as the field "name" inside the json configuration file;
  • CAPIO_APP_NAME: This environment variable defines the app name within a workflow for a given step;