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dtrace pid provider hooks for mri

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README.textile

MRI Instrumentation

There’s a lot of black magic and speculation as to the inner workings of the Ruby VM.This is an experiment with MRI internals that :

  • is supported on OS X Leopard, Solaris and any other dtrace enabled environment
  • is unobtrusive – use whichever Ruby 18 version you already have installed
  • expects probe definitions to be structured as YAML for possible porting to other dynamic tracing frameworks

How the dtrace PID provider works

A set of C level probes is spawned for the lifetime of a given command or existing process.When the process dies, the probe’s is unset.You don’t have to recompile or relink – it just works.

Why bother ?

A dtrace environment is available to most ruby developers, offers fast dynamic runtime instrumentation and the D language is well suited for presenting data through different visual strategies.

This package is primarily aimed at framework style development where deep instrumentation may yield significant insight into potential performance hotspots.

Installation


	git clone git://github.com/methodmissing/mri_instrumentation.git
	cd mri_instrumentation
	ruby bin/instrument --help

Probe definitions:

Through YAML everyone can be a C buff :


	rb_clear_cache: 
	rb_clear_cache_by_id:
	rb_clear_cache_by_class:

Probes can also define arguments and expected return values :


	rb_clear_cache_by_id:
      args:
        - int: 'Id'
      return: void

Although support’s built in for coersion etc. I’ve found working with void returns and pointer arguments to be somewhat problematic, hence the barebones argumentless definitions.It’ll be fixed real soon.

Usage examples

Early days, but one of the following instrumentation modes is supported :

  • attach to a running PID
  • run / spawn a new ruby process

Various different profiling strategies would be supported, but we’re shipping with a conservative calltime strategy in this initial release.Expect execution flow, stack traces on error conditions etc. as potential future options.


	213-138-231-176:mri_instrumentation lourens$ ruby bin/instrument --help
	Usage: instrument [OPTIONS] probe1 probe2 probe3
	MRI instrumentation with the dtrace pid provider
	  -pid=[val]                       The process identifier (PID) to attach to
	                                   Default: 0
	  -cmd=[val]                       The command to run
	                                   Default: 
	  -strategy=[val]                  The desired profiling strategy
	                                   Default: calltime
	  -h, --help                       Show this help message.

MRI’s internal method cache


	213-138-231-176:mri_instrumentation lourens$ ruby bin/instrument -c /Users/lourens/projects/superbreak_app/script/console cache
	./bin/../lib/mri/instrumentation/runner/base.rb:86: warning: Insecure world writable dir /Users/lourens in PATH, mode 040753
	Loading development environment (Rails 2.3.2)
	/Users/lourens/projects/superbreak_app/vendor/rails/railties/lib/commands/console.rb:45: warning: Insecure world writable dir /Users/lourens in PATH, mode 040753
	Tracing... Hit Ctrl-C to end.
	>> exit

	Count,
	   Probe                                   COUNT
	   rb_clear_cache                             43
	   rb_clear_cache_by_class                    89
	   rb_clear_cache_by_id                     3266

	Exclusive function elapsed times (us),
	   Probe                                   TOTAL
	   rb_clear_cache                            258
	   rb_clear_cache_by_class                   691
	   rb_clear_cache_by_id                    15553

	Inclusive function elapsed times (us),
	   Probe                                   TOTAL
	   rb_clear_cache                            258
	   rb_clear_cache_by_class                   691
	   rb_clear_cache_by_id                    15553	

What blocks have been up to


	213-138-231-176:mri_instrumentation lourens$ ruby bin/instrument -c /Users/lourens/projects/superbreak_app/script/console block
	./bin/../lib/mri/instrumentation/runner/base.rb:86: warning: Insecure world writable dir /Users/lourens in PATH, mode 040753
	Loading development environment (Rails 2.3.2)
	/Users/lourens/projects/superbreak_app/vendor/rails/railties/lib/commands/console.rb:45: warning: Insecure world writable dir /Users/lourens in PATH, mode 040753
	Tracing... Hit Ctrl-C to end.
	>> exit

	Count,
	   Probe                                   COUNT
	   yield_under                                 1
	   yield_under_i                               1
	   blk_copy_prev                              11
	   blk_free                                   12
	   blk_dup                                    20
	   blk_mark                                   58
	   block_pass                                 62
	   rb_yield                                  862
	   rb_need_block                             882
	   rb_yield_0                                882
	   rb_block_given_p                         1641

	Exclusive function elapsed times (us),
	   Probe                                   TOTAL
	   yield_under_i                              17
	   yield_under                                26
	   blk_copy_prev                              70
	   blk_free                                   73
	   blk_dup                                   102
	   blk_mark                                  635
	   block_pass                               1187
	   rb_block_given_p                         6320
	   rb_yield                                15681
	   rb_need_block                           18327
	   rb_yield_0                              36787

	Inclusive function elapsed times (us),
	   Probe                                   TOTAL
	   yield_under_i                              57
	   blk_copy_prev                              70
	   blk_free                                   73
	   yield_under                                83
	   blk_dup                                   102
	   blk_mark                                  718
	   block_pass                               1639
	   rb_block_given_p                         6320
	   rb_need_block                           21705
	   rb_yield_0                              87886
	   rb_yield                                98256

Garbage Collection


	213-138-231-176:mri_instrumentation lourens$ ruby bin/instrument -c /Users/lourens/projects/superbreak_app/script/console gc
	./bin/../lib/mri/instrumentation/runner/base.rb:86: warning: Insecure world writable dir /Users/lourens in PATH, mode 040753
	Tracing... Hit Ctrl-C to end.
	Loading development environment (Rails 2.3.2)
	/Users/lourens/projects/superbreak_app/vendor/rails/railties/lib/commands/console.rb:45: warning: Insecure world writable dir /Users/lourens in PATH, mode 040753
	>> exit

	Count,
	   Probe                                   COUNT
	   rb_gc_unregister_address                    1
	   add_heap                                    4
	   free_unused_heaps                           4
	   garbage_collect                             4
	   rb_gc_mark_locations                        5
	   mark_locations_array                        9
	   rb_mark_tbl                                 9
	   rb_global_variable                         22
	   mark_hash                                  23
	   rb_gc_register_address                     23
	   sweep_source_filename                      91
	   rb_data_object_alloc                      114
	   rb_source_filename                        129
	   rb_gc_mark_frame                          163
	   rb_gc_mark_maybe                          222
	   rb_gc_mark                                575
	   ruby_stack_check                          601
	   stack_end_address                         605
	   mark_keyvalue                             891
	   ruby_xcalloc                             1361
	   ruby_xfree                               1596
	   ruby_xrealloc                            3053
	   mark_tbl                                 3701
	   rb_gc_force_recycle                      6158
	   mark_entry                              15342
	   ruby_xmalloc                            45903
	   gc_mark_children                        53783
	   gc_mark                                 74469
	   mark_source_filename                    93431
	   rb_newobj                               96586

	Exclusive function elapsed times (us),
	   Probe                                   TOTAL
	   rb_gc_unregister_address                    4
	   free_unused_heaps                          19
	   rb_gc_mark_locations                       23
	   rb_mark_tbl                                34
	   rb_global_variable                         91
	   mark_locations_array                      136
	   sweep_source_filename                     308
	   rb_gc_register_address                    407
	   rb_gc_mark_frame                          608
	   rb_gc_mark_maybe                          710
	   rb_gc_mark                               2003
	   rb_data_object_alloc                     2015
	   rb_source_filename                       2050
	   stack_end_address                        2457
	   add_heap                                 2805
	   ruby_xfree                               6334
	   ruby_xrealloc                           11883
	   ruby_stack_check                        12954
	   mark_hash                               14022
	   rb_gc_force_recycle                     21856
	   ruby_xcalloc                            23749
	   mark_keyvalue                           44226
	   ruby_xmalloc                           173719
	   mark_tbl                               199721
	   gc_mark                                277730
	   mark_source_filename                   332414
	   rb_newobj                              341314
	   mark_entry                             393127
	   gc_mark_children                      3122918

	Inclusive function elapsed times (us),
	   Probe                                   TOTAL
	   rb_gc_unregister_address                    4
	   free_unused_heaps                          19
	   rb_gc_mark_locations                       23
	   rb_mark_tbl                                34
	   rb_global_variable                         91
	   sweep_source_filename                     308
	   rb_gc_register_address                    489
	   mark_locations_array                      500
	   rb_gc_mark_frame                          608
	   rb_gc_mark_maybe                          710
	   rb_gc_mark                               2003
	   rb_data_object_alloc                     2437
	   rb_source_filename                       2456
	   stack_end_address                        2457
	   add_heap                                 2805
	   ruby_xfree                               6334
	   ruby_xrealloc                           11883
	   ruby_stack_check                        15396
	   rb_gc_force_recycle                     21856
	   ruby_xcalloc                            28800
	   mark_keyvalue                           92162
	   mark_hash                              106184
	   ruby_xmalloc                           173719
	   gc_mark                                291686
	   mark_source_filename                   332414
	   rb_newobj                              341314
	   mark_tbl                              1905278
	   mark_entry                            4311987
	   gc_mark_children                     18471501	

Thanks for reading – on holidays for the next 3 weeks, expect updates to be sporadic and patchy during that time.

© 2009 Lourens Naudé (methodmissing)

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