DMD currently uses a very hacky form of "sampling" by default to avoid
recording stack traces for all blocks. This makes DMD run faster than when it
records all stack traces.
This patch changes the sampling method used; in fact, it avoids "sampling" at
all. The existence of all heap blocks is now recorded exactly, but by default
we only record an allocation stack for each heap block if a Bernoulli trial
succeeds. This choice works well because getting the stack trace is ~100x
slower than recording the block's existence.
Overall, this approach is simpler and it also gives better output -- the choice
of which blocks to record allocation stacks for is mathematically sound, no
stack trace gets blamed for allocations it didn't do, and block counts and
sizes are now always exact.
Other specific things changed.
- All notion of sampling is removed from the various data structures.
- The --sample-below option is removed in favour of --stacks={partial,full}.
- The format of the JSON output file has changed.
- The names of various test files have changed to reflect concept changes.
--HG--
rename : memory/replace/dmd/test/full-empty-cumulative-expected.txt => memory/replace/dmd/test/complete-empty-cumulative-expected.txt
rename : memory/replace/dmd/test/full-empty-dark-matter-expected.txt => memory/replace/dmd/test/complete-empty-dark-matter-expected.txt
rename : memory/replace/dmd/test/full-empty-live-expected.txt => memory/replace/dmd/test/complete-empty-live-expected.txt
rename : memory/replace/dmd/test/full-unsampled1-dark-matter-expected.txt => memory/replace/dmd/test/complete-full1-dark-matter-expected.txt
rename : memory/replace/dmd/test/full-unsampled1-live-expected.txt => memory/replace/dmd/test/complete-full1-live-expected.txt
rename : memory/replace/dmd/test/full-unsampled2-cumulative-expected.txt => memory/replace/dmd/test/complete-full2-cumulative-expected.txt
rename : memory/replace/dmd/test/full-unsampled2-dark-matter-expected.txt => memory/replace/dmd/test/complete-full2-dark-matter-expected.txt
rename : memory/replace/dmd/test/full-sampled-live-expected.txt => memory/replace/dmd/test/complete-partial-live-expected.txt
extra : rebase_source : 47d287405dc5e9075f08addaba49e879c2c6e23f
This implements a new "scan" mode for DMD that records the address
and contents of every live unsampled block in the DMD log. This
enables the low-level analysis of references from one block to
another, which can help leak investigations.
The new "num" property lets identical blocks be aggregated in the output. This
patch only uses the "num" property for dead blocks, because that's where the
greatest potential benefit lies, but it could be used for live blocks as well.
On one test case (a complex PDF file) running with --mode=cumulative
--sample-below=1 this patch had the following effects.
- Change in running speed was negligible.
- Compressed output file size dropped from 8.8 to 5.0 MB.
- Compressed output file size dropped from 297 to 50 MB.
- dmd.py runtime (without stack fixing) dropped from 30 to 8 seconds.
--HG--
extra : rebase_source : 46a32058cd5c31cd823fe3f1accb5e68bcd320f3
Now that defining $DMD is no longer necessary to run DMD, this patch does the
following.
- Removes all the places where we set DMD=1 (test harnesses, etc.)
- Still handles DMD=1, for backwards compatibility.
- Prints "$DMD is undefined" at DMD start-up if appropriate.
- Writes a |null| value for |dmdEnvVar| in the JSON if $DMD is undefined. Bumps
the DMD output version number accordingly.
- Changes a bunch of the test files accordingly, including changing the mode of
script-ignore-alloc-fns.json in order to test a case where $DMD is undefined.
--HG--
extra : rebase_source : eb1ef5722410734ce6d7658465ff6f442ee4ed49
This patch moves profiling mode selection from post-processing (in dmd.py) to
DMD start-up. This will make it easier to add new kinds of profiling, such as
cumulative heap profiling.
Specifically:
- There's a new --mode option. |LiveWithReports| is the default, as it is
currently.
- dmd.py's --ignore-reports option is gone.
- There's a new |mode| field in the JSON output.
- Reports-related operations are now no-ops if DMD isn't in LiveWithReports
mode.
- Diffs are only allowed for output files that have the same mode.
- A new function ResetEverything() replaces the SetSampleBelowSize() and
ClearBlocks(), which were used by the test to change DMD options.
- The tests in SmokeDMD.cpp are split up so they can be run multiple times, in
different modes. The exact combinations of tests and modes has been changed a
bit.
--HG--
rename : memory/replace/dmd/test/full-reports-empty-expected.txt => memory/replace/dmd/test/full-empty-dark-matter-expected.txt
rename : memory/replace/dmd/test/full-heap-empty-expected.txt => memory/replace/dmd/test/full-empty-live-expected.txt
rename : memory/replace/dmd/test/full-heap-sampled-expected.txt => memory/replace/dmd/test/full-sampled-live-expected.txt
rename : memory/replace/dmd/test/full-reports-unsampled1-expected.txt => memory/replace/dmd/test/full-unsampled1-dark-matter-expected.txt
rename : memory/replace/dmd/test/full-heap-unsampled1-expected.txt => memory/replace/dmd/test/full-unsampled1-live-expected.txt
rename : memory/replace/dmd/test/full-reports-unsampled2-expected.txt => memory/replace/dmd/test/full-unsampled2-dark-matter-expected.txt
rename : memory/replace/dmd/test/script-diff-basic-expected.txt => memory/replace/dmd/test/script-diff-live-expected.txt
rename : memory/replace/dmd/test/script-diff1.json => memory/replace/dmd/test/script-diff-live1.json
rename : memory/replace/dmd/test/script-diff2.json => memory/replace/dmd/test/script-diff-live2.json
extra : rebase_source : bf32cc4e0d82aa1a20ceb55e8ea259850b49cc06
Because DMD is no longer just about measuring memory reports coverage, but is
also used for more general heap profiling.
--HG--
extra : rebase_source : 82b4579de240037f96cf6618b15870925adc431b
This is to give better contrast with |DeadBlock|, which will be added in the
next patch.
--HG--
extra : rebase_source : cbc767fcc5667cfed108ca7c4ebf1d7e82aa185e
This also effectively changes how DMD is enabled from requiring both
replace-malloc initialization and the DMD environment variable to
requiring only the former. The DMD environment variable can still be
used to specify options, but not to disable entirely.
This however doesn't touch all the parts that do enable DMD by setting
the DMD environment variable to 1, so the code to handle this value
is kept.
The interesting feature JSONWriteFunc has, contrary to JSONWriter, is that it
only has virtual methods, which makes it a better candidate to be passed
around between libraries not linked against each other.
This will allow to make dmd and libxul independent from each other.
The patch also adds DMDAnalyzeReports() as a synonym for DMDReportAndDump(),
and deprecates the latter.
--HG--
extra : rebase_source : 651246aa7a0a301f804c124f25beb0e8ed6cd67f
Nicholas Nethercote
Jonathan Watt
Andrew McCreight
Mike Hommey
Carsten "Tomcat" Book
Eric Rahm
Nathan Froyd
Justin Lebar