[Git][ghc/ghc][master] 2 commits: users guide: Fix syntax errors
Marge Bot
gitlab at gitlab.haskell.org
Fri Dec 11 08:55:58 UTC 2020
Marge Bot pushed to branch master at Glasgow Haskell Compiler / GHC
Commits:
ab24ed9b by Ben Gamari at 2020-12-11T03:55:51-05:00
users guide: Fix syntax errors
Fixes errors introduced by 3a55b3a2574f913d046f3a6f82db48d7f6df32e3.
- - - - -
d3a24d31 by Ben Gamari at 2020-12-11T03:55:51-05:00
users guide: Describe GC lifecycle events
Every time I am asked about how to interpret these events I need to
figure it out from scratch. It's well past time that the users guide
properly documents these.
- - - - -
4 changed files:
- docs/users_guide/eventlog-formats.rst
- docs/users_guide/runtime_control.rst
- docs/users_guide/using-optimisation.rst
- rts/Stats.c
Changes:
=====================================
docs/users_guide/eventlog-formats.rst
=====================================
@@ -207,9 +207,61 @@ Thread and scheduling events
:base-ref:`Control.Concurrent.setThreadLabel`).
+.. _gc-events:
+
Garbage collector events
~~~~~~~~~~~~~~~~~~~~~~~~
+The following events mark various points of the lifecycle of a moving garbage
+collection.
+
+A typical garbage collection will look something like the following:
+
+1. A capability realizes that it needs a garbage collection (e.g. as a result
+ of running out of nursery) and requests a garbage collection. This is
+ marked by :event-type:`REQUEST_SEQ_GC` or :event-type:`REQUEST_PAR_GC`.
+
+2. As other capabilities reach yield points and suspend execution they emit
+ :event-type:`STOP_THREAD` events.
+
+3. When all capabilities have suspended execution, collection will begin,
+ marked by a :event-type:`GC_START` event.
+
+4. As individual parallel GC threads commence with scavenging they will emit
+ :event-type:`GC_WORK` events.
+
+5. If a parallel GC thread runs out of work it will emit a
+ :event-type:`GC_IDLE` event. If it is later handed more work it will emit
+ another :event-type:`GC_WORK` event.
+
+6. Eventually when scavenging has finished a :event-type:`GC_DONE` event
+ will be emitted by each GC thread.
+
+7. A bit of book-keeping is performed.
+
+8. A :event-type:`GC_END` event will be emitted marking the end of the GC cycle.
+
+9. A :event-type:`HEAP_SIZE` event will be emitted giving the
+ cumulative heap allocations of the program until now.
+
+10. A :event-type:`GC_STATS_GHC` event will be emitted
+ containing various details of the collection and heap state.
+
+11. In the case of a major collection, a
+ :event-type:`HEAP_LIVE` event will be emitted describing
+ the current size of the live on-heap data.
+
+12. In the case of the :ghc-flag:`-threaded` RTS, a
+ :event-type:`SPARK_COUNTERS` event will be emitted giving
+ details on how many sparks have been created, evaluated, and GC'd.
+
+13. As mutator threads resume execution they will emit :event-type:`RUN_THREAD`
+ events.
+
+Note that in the case of the concurrent non-moving collector additional events
+will be emitted during the concurrent phase of collection. These are described
+in :ref:`nonmoving-gc-events`.
+
.. event-type:: GC_START
:tag: 9
@@ -685,6 +737,46 @@ These events mark various stages of the
:rts-flag:`non-moving collection <--nonmoving-gc>` lifecycle. These are enabled
with the ``+RTS -lg`` event-set.
+A typical non-moving collection cycle will look something like the following:
+
+1. The preparatory phase of collection will emit the usual events associated
+ with a moving collection. See :ref:`gc-events` for details.
+
+2. The concurrent write barrier is enabled and the concurrent mark thread is
+ started. From this point forward mutator threads may emit
+ :event-type:`CONC_UPD_REM_SET_FLUSH` events, indicating that they have
+ flushed their capability-local update remembered sets.
+
+3. Concurrent marking begins, denoted by a :event-type:`CONC_MARK_BEGIN` event.
+
+4. When the mark queue is depleted a :event-type:`CONC_MARK_END` is emitted.
+
+5. If necessary (e.g. due to weak pointer marking), the marking process will
+ continue, returning to step (3) above.
+
+6. When the collector has done as much concurrent marking as it can it will
+ enter the post-mark synchronization phase of collection, denoted by a
+ :event-type:`CONC_SYNC_BEGIN` event.
+
+7. Mutator threads will suspend execution and, if necessary, flush their update
+ remembered sets (indicated by :event-type:`CONC_UPD_REM_SET_FLUSH` events).
+
+8. The collector will do any final marking necessary (indicated by
+ :event-type:`CONC_MARK_BEGIN` and :event-type:`CONC_MARK_END` events).
+
+9. The collector will do a small amount of sweeping, disable the write barrier,
+ emit a :event-type:`CONC_SYNC_END` event, and allow mutators to resume
+
+10. The collector will begin the concurrent sweep phase, indicated by a
+ :event-type:`CONC_SWEEP_BEGIN` event.
+
+11. Once sweeping has concluded a :event-type:`CONC_SWEEP_END` event will be
+ emitted and the concurrent collector thread will terminate.
+
+12. A :event-type:`NONMOVING_HEAP_CENSUS` event will be emitted describing the
+ fragmentation state of the non-moving heap.
+
+
.. event-type:: CONC_MARK_BEGIN
:tag: 200
@@ -742,8 +834,9 @@ with the ``+RTS -lg`` event-set.
Non-moving heap census
~~~~~~~~~~~~~~~~~~~~~~
-The non-moving heap census events (enabled with the ``+RTS -ln`` event-set) are
-intended to provide insight into fragmentation of the non-moving heap.
+The non-moving heap census events (enabled with the :rts-flag:`+RTS -ln <-l ⟨flags⟩>`
+event-set) are intended to provide insight into fragmentation of the non-moving
+heap.
.. event-type:: NONMOVING_HEAP_CENSUS
@@ -760,8 +853,8 @@ Ticky counters
~~~~~~~~~~~~~~
Programs compiled with :ghc-flag:`-ticky` and :ghc-flag:`-eventlog` and invoked
-with ``+RTS -lT`` will emit periodic samples of the ticky entry counters to the
-eventlog.
+with :rts-flag:`+RTS -lT <-l ⟨flags⟩>` will emit periodic samples of the ticky
+entry counters to the eventlog.
.. event-type:: TICKY_COUNTER_DEF
=====================================
docs/users_guide/runtime_control.rst
=====================================
@@ -1194,6 +1194,9 @@ When the program is linked with the :ghc-flag:`-eventlog` option
- ``f`` — parallel sparks (fully accurate). Disabled by default.
+ - ``T`` — :ghc-flag:`ticky-ticky profiler <-ticky>` events. Disabled by
+ default.
+
- ``u`` — user events. These are events emitted from Haskell code using
functions such as ``Debug.Trace.traceEvent``. Enabled by default.
=====================================
docs/users_guide/using-optimisation.rst
=====================================
@@ -1197,16 +1197,16 @@ by saying ``-fno-wombat``.
This is the full syntax for cardinalities, demands and sub-demands in BNF:
- .. code-block::
+ .. code-block:: none
- card ::= B | A | 1 | U | S | M semantics as in the table above
+ card ::= B | A | 1 | U | S | M semantics as in the table above
- d ::= card sd card = how often, sd = how deep
- | card abbreviation: Same as "card card"
+ d ::= card sd card = how often, sd = how deep
+ | card abbreviation: Same as "card card"
- sd ::= card polymorphic sub-demand, card at every level
- | P(d,d,..) product sub-demand
- | Ccard(sd) call sub-demand
+ sd ::= card polymorphic sub-demand, card at every level
+ | P(d,d,..) product sub-demand
+ | Ccard(sd) call sub-demand
For example, ``fst`` is strict in its argument, and also in the first
component of the argument. It will not evaluate the argument's second
@@ -1234,17 +1234,17 @@ by saying ``-fno-wombat``.
We summarise a function's demand properties in its *demand signature*.
This is the general syntax:
- .. code-block::
+ .. code-block:: none
- {x->dx,y->dy,z->dz...}<d1><d2><d3>...<dn>div
- ^ ^ ^ ^ ^ ^
- | | | | | |
- | \---+---+------/ |
- | | |
- demand on free demand on divergence
- variables arguments information
- (omitted if empty) (omitted if
- no information)
+ {x->dx,y->dy,z->dz...}<d1><d2><d3>...<dn>div
+ ^ ^ ^ ^ ^ ^
+ | | | | | |
+ | \---+---+------/ |
+ | | |
+ demand on free demand on divergence
+ variables arguments information
+ (omitted if empty) (omitted if
+ no information)
We summarise ``fst``'s demand properties in its *demand signature*
``<SP(SU,A)>``, which just says "If ``fst`` is applied to one argument,
@@ -1260,13 +1260,11 @@ by saying ``-fno-wombat``.
**Call sub-demands**
- Consider ``maybe``:
+ Consider ``maybe``: ::
- .. code-block::
-
- maybe :: b -> (a -> b) -> Maybe a -> b
- maybe n _ Nothing = n
- maybe _ s (Just a) = s a
+ maybe :: b -> (a -> b) -> Maybe a -> b
+ maybe n _ Nothing = n
+ maybe _ s (Just a) = s a
We give it demand signature ``<U><1C1(U)><SU>``. The ``C1(U)`` is a *call
sub-demand* that says "Called at most once, where the result is used
=====================================
rts/Stats.c
=====================================
@@ -570,7 +570,7 @@ stat_endGC (Capability *cap, gc_thread *initiating_gct, W_ live, W_ copied, W_ s
// Emit events to the event log
// Has to be emitted while all caps stopped for GC, but before GC_END.
- // See trac.haskell.org/ThreadScope/wiki/RTSsummaryEvents
+ // See https://gitlab.haskell.org/ghc/ghc/-/wikis/RTSsummaryEvents
// for a detailed design rationale of the current setup
// of GC eventlog events.
traceEventGcGlobalSync(cap);
View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/6484f0d72a9110c5960b9185f239e6ce049b0c74...d3a24d3190de47044981363329337c16b5052028
--
View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/6484f0d72a9110c5960b9185f239e6ce049b0c74...d3a24d3190de47044981363329337c16b5052028
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