NAME

Devel::Arena - Perl extension for inspecting the core's arena structures

SYNOPSIS

use Devel::Arena 'sv_stats';
# Get hash ref describing the arenas for SV heads
$sv_stats = sv_stats;

DESCRIPTION

Inspect the arena structures that perl uses for SV allocation.

HARNESS_PERL_SWITCHES=-MDevel::Arena=write_stats_at_END make test

EXPORT

None by default.

• sv_stats [DONT_SHARE]

  Returns a hashref giving stats derived from inspecting the SV heads via the arena pointers. Details of the contents of the hash subject to change.

  If the optional argument DONT_SHARE is true then none of the hashes in the returned structure have shared hash keys. This is less efficient, but is needed to calculate the effectiveness of the shared string table.

• shared_string_table

  Returns a hashref giving the share counts for each entry in the shared string table. The hashref doesn't use shared keys itself, so it doesn't affect the thing that it is measuring.

• sizes

  Returns a hashref containing sizes of various core perl types, C types, and other size related info (specifically 'hek_key offset')

• HEK_size STRING

  Calculates the size of the hash key needed to store STRING.

• shared_string_table_effectiveness

  Calculates the effectiveness of the shared string table. Returns a hashref of stats. Currently this is

  {
    'pv_unshared' => 7185,
    'raw_unshared' => 77264,
    'heks' => 3748,
    'pv_hv' => 77264,
    'hv_unshared' => 70079,
    'raw_shared' => 57675,
    'pvs' => 434,
    'raw' => 1833
  };

  It ignores malloc() overhead, and the possibility that some shared strings aren't used as hash keys or shared hash key scalars.

• write_stats_at_END

  Not really a function, but if you import write_stats_at_END then Devel::Arena will write out a Storable dump of all stats at END time. The file is written into a file into a file in the current directory named $$ . '.sv_stats'. This allows you to do things such as

  HARNESS_PERL_SWITCHES=-MDevel::Arena=write_stats_at_END make test

  to analyse the resource usage in regression tests.

SEE ALSO

sv.c in the perl core.

AUTHOR

Nicholas Clark, <nick@ccl4.org>

COPYRIGHT AND LICENSE

Copyright (C) 2005, 2006 by Nicholas Clark

This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself, either Perl version 5.8.6 or, at your option, any later version of Perl 5 you may have available.