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Since it's been quite a while since I've written C code, *and* I
haven't done any significant hacking on the VM itself in years, it's
quite likely that I haven't done things in 100% proper style. Or
my co-collaborators Dustin Sallings (CouchBase) or Michal Ptaszek
(Erlang Solutions). My intent for this patch is to start discussion
and review of DTrace support for consideration for the R15 release.
For additional background on the motivation for this work, please
see the slides for the presentation at the Erlang User Conference 2011
in Stockholm:
https://www.erlang-factory.com/upload/presentations/462/euc2011-draft2.pdf
Changes relative to dtrace-review2 branch:
* Fix errors in OTP test suite 'kernel' file_SUITE
* Fix errors in OTP test suite 'kernel' prim_file_SUITE
* Fix bad pointer bug in efile_drv.c flush_write()
* Move the DTrace material from the top of `README.md` into a
new file, `README.dtrace.md`
Changes since last push to GitHub (relative to commit 5828a4fb28, which
was the former `dtrace-review1` branch):
* Rebased onto 14 Nov 2011's "master" branch
* Recent changes to the async task queuing mechanism means that
the async worker queue length is not available. A bogus value
of -1 is hard-coded until there's a good way to peek into the
new queue structure and find the queue length.
* Small fixes based on review comments by Mikael Pettersson,
Andrew Thompson, and Andreas Schultz.
Add autoconf support: use "./configure --enable-dtrace" on all supported
platforms:
* OS X Snow Leopard or later
* Solaris 10 or OpenSolaris
* Linux, via SystemTap's DTrace compatibility packages
* FreeBSD 9.0RC1. FreeBSD 8 and earlier do not have support
for USDT, DTrace's User-land Statically Defined Tracing.
See the file `erts/emulator/beam/erlang_dtrace.d` for the definition
of all DTrace probes in the virtual machine so far.
Example D scripts can be found in `lib/dtrace/examples`. Note that if
you see the error message `{name of probe} does not match any probes`,
then there is no Erlang VM process + DTrace probes running. To fix,
start a DTrace-enabled VM or remove `-q` from the `dtrace` command line.
The `lib/dtrace` directory contains a small code-only OTP application
that contains code that allows Erlang code to trigger a DTrace probe.
Dynamic creation & deletion of DTrace probes is not currently
supported, so the `dtrace:p()` function is hacked to allow a variable
number of arguments (up to four integers and up to four strings) to be
used. See the comments at the top of `lib/dtrace/src/dtrace.c` for
more detail.
One feature that may be controversial is the notion I've introduced
of a special process dictionary key that can be used by Erlang code to
tag I/O operations for an application-specific purpose. Right now,
that tag's name is `dtrace_utag`. The dictionary keys used by `sys`
and other modules start with a dollar sign. Perhaps there is some
convention (but not a dollar sign?) that this tag should use?
The purpose of the process dictionary key is to allow the tag to
be included in trace messages, e.g. for file I/O, without changing the
API of the `file.erl` module's functions. For example, here's a use
of the tag when calling the `file:rename/2` function:
(bar@sbb2)1> put(dtrace_utag, "GGOOOAAALL!!!!!").
undefined
(bar@sbb2)2> dtrace:init().
ok
%% Now start both the `user-probe.d` and `efile_drv.d` D scripts
%% found in the `lib/dtrace/examples` directory.
(bar@sbb2)3> dtrace:p(7, 8, 9, "one", "four").
true
%% The output from the `user-probe.d` script:
<0.40.0> GGOOOAAALL!!!!! 7 8 9 0 'one' 'four' '' ''
(bar@sbb2)4> file:rename("old-name", "new-name").
{error,enoent}
%% The output from the `efile_drv.d` script:
async I/O pool port #Port<0.59> queue len 1
async I/O pool port #Port<0.59> queue len 0
efile_drv enter tag={1,110} user tag GGOOOAAALL!!!!! | RENAME (12) | args: old-name new-name , 0 0 (port #Port<0.59>)
async I/O worker tag={1,110} | RENAME (12) | efile_drv-int_entry
async I/O worker tag={1,110} | RENAME (12) | efile_drv-int_return
efile_drv return tag={1,110} user tag GGOOOAAALL!!!!! | RENAME (12) | errno 2
I'm not exactly happy with this choice of tagging, namely using
`put(dtrace_utag, Tag::list())`. But this is an experiment, so
we'll see how it goes. I can't imagine changing the API for
all file.erl functions in order pass the tag explicitly.
Some modules have some extensive (ab)use of the C preprocessor to
reduce the amount of #ifdefs that clutter the code. In several places,
I have not #ifdef'ed automatic variables because of clutter. For the
same reason, there are a handful of cases where I added DTrace-related
members to a struct definition without an #ifdef. I feel that the
result is easier to read than earlier drafts where I did use many more
`https://github.com/slfritchie/otp/tree/dtrace-experiment+michal2` if
you're curious.) I expect there may be some debate about whether the
bloat of the affected structs is worthwhile. I erred on adding stuff
to structs, especially in the efile_drv.c driver, not having a full
grasp on what was thread-safe and what was not ... so I erred on the
side of caution.
The efile_drv.c has a work-around for a crazy GCC optimization bug.
Thank goodness for Google, I dunno how I would've found a work-around
for this silly thing. Many thanks to Trond Norbye for writing clearly
about the problem in a membase Git repo commit message.
/*
* A note on probe naming: if "__" appears in a provider probe
* definition, then two things happen during compilation:
*
* 1. The "__" will turn into a hypen, "-", for the probe name.
* 2. The "__" will turn into a single underscore, "_", for the
* macro names and function definitions that the compiler and
* C developers will see.
*
* We'll try to use the following naming convention. We're a bit
* limited because, as a USDT probe, we can only specify the 4th part
* of the probe name, e.g. erlang*:::mumble. The 2nd part of the
* probe name is always going to be "beam" or "beam.smp", and the 3rd
* part of the probe name will always be the name of the function
* that's calling the probe.
*
* So, all probes will be have names defined in this file using the
* convention category__name or category__sub_category__name. This
* will translate to probe names of category-name or
* category-sub_category-name.
*
* Each of "category", "sub_category", and "name" may have underscores
* but may not have hyphens.
*/
Add tentative support for sequential tracing sending, queueing, and
receiving a message. I don't believe I've fully covered all the major
places where it would be useful to have the sequential trace token info
in a probe -- guidance from the OTP team would be helpful, if there's
time to do that kind of review.
Add global variable `erts_this_node_sysname`.
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* raimo/close-ports-on-halt/OTP-9985:
erts: Basic test of erlang:halt/0..2
erts: Document erlang:halt/2 and update erlang:halt/0,1
erts: Implement erlang:halt/2
stdlib: Stop working around erlang:halt not flushing
erts: Make erlang:halt/0,1 close ports and flush async threads
erts: Remove forgotten and unused function erl_exit0
erts: Implement erl_halt
erts: Remove unused ntbuild.erl
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* ia/public_key/prepare-for-release:
Prepare for release
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* ia/ssh/prepare-for-release:
Prepare for release
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* ia/ssl/prepare-for-release:
Prepare for release
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OTP-9792
OTP-9794
OTP-9967
OTP-9968
OTP-9980
OTP-9984
* siri/reltool/fresh-up: (27 commits)
[reltool] Improve title of dependency colum
[reltool] Update status bar for all config changes and for generate target
[reltool] Fix GUI problems on Windows
[reltool] Remove skip statement for test that failed due to stdlib error
[sasl] Sort applications used by other applications correctly in .script
[sasl] Doc that included applications in .rel defaults to same as in .app
[reltool] Fix problems with sorting of applications
[reltool] Just warn if same module occurs twice in .app file
[reltool] Always return warnings as flat strings
[reltool] Fix type spec and doc for app() and mod()
[reltool] Move tables out of common record
[reltool] Display warnings continously in GUI
[reltool] Cleanup test code
[reltool] Unset ERL_FLAGS when running escript from reltool_server_SUITE
[reltool] Improve error handling
[reltool] Fix rollback and undo
[reltool] Link together escript with inlined application
[reltool] Fix badmatch when starting GUI
[reltool] Update state and tables consistently for all types of config changes
[reltool] Add test cases for handling of escripts
...
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* lukas/common_test/add_surefire_hook/OTP-9995:
Add the surefire ct hook
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* pan/testcase-fix-bigboot:
Align java test Makefile.src with c tests ditto in ic
Teach ei testsuites parallel make
Teach edlin_expand_SUITE:init_per_suite independence
Teach big_boot_embedded testcase about comte
OTP-10008
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* pan/remove_temp_files_io_proto_SUITE:
io_proto_SUITE: make sure temp files are removed
OTP-10005
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* pan/win_doc_fix/OTP-9846:
Correct build instruction for 32bit OpenSSL
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Also made some visual improvements to the example command lines
for wxWidgets/OpenSSL and made some minor updates to the
build instructions for those libraries.
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Updates for ssh that needs to restarted so no need for soft upgrade
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* dgud/observer/fix-mem-graph:
[observer] Remove system from memory graph
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* dgud/wx/misc-improvements/OTP-9947:
[wx] Add more types
[wx] Fix listctrl issues
[wx] Fix bad defines
[wx] Fix bad type references
[wx] Fix missing export_types
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* dgud/debugger/breakpoints_bug/OTP-9950:
[debugger] Fixed disappearing breakpoints
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Supervisor tree changed so can not do soft upgrade
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Distribution fixes so no need to soft upgrade.
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* hb/kernel/too_greedy_disk_log/OTP-9999:
Make sure disk_log does not write too much data
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* hb/stdlib/fix_qlc_suite/OTP-10000:
Correct a minor bug in qlc's testsuite
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* lars/xmerl/continuation-error/OTP-9961:
Fix continuation error
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* lars/xmerl/remove-unused-file/OTP-9965:
Remove unused file
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It is confusing we have total and system is total - processes
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* sverk/cpu-topology-crash:
erts: Fix memory corruption when reading topology info
OTP-10004
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The hook should work with modern versions of Jenkins CI
to gather test results.
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While disk_log eagerly collects logged data for better performance,
collecting too much data may choke the system and cause huge binaries
to be written.
The problem was addressed in OTP-9764, but the situation was not
improved in all cases.
Thanks to Richard Carlsson.
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* gustav/ic/remove-warnings:
Bump version from 4.2.29 to 4.2.30
Add generation of Erlang callback functions to avoid
compiler warnings of generated Erlang source code
Seq12023
OTP-9998
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OTP-9792
The colum listing modules that uses the current application or module
did earlier have the title "Modules used by others". This is now
changed to "Modules using this".
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* dc/dch-fix-win32-escript:
add escript win32 alternative invocation (thanks Pierre Rouleau)
OTP-9997
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OTP-9792
For some configuration changes and during generation of target system,
there was no indication in the status bar that reltool was
working. This has been corrected - it now says "Processing
libraries...".
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* sverk/zlib_port_leak:
Fix port leaks in zlib
OTP-9981
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* ps/inet6-less-build-fix:
Add missing HAVE_IN6 && AF_INET6 ifdef
OTP-9996
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* lukas/kernel/sendfile_fixes:
Fix reselecting bug on OS X
Fix bug when sending long files using select
Fix ifdef to check if we are on OS X
Add test case for sending multiple small files on same connection
Fix memory leak when sendfile process crashes
Extend timeout for windows
Skip sendfile suite if solaris 8
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