[Git][ghc/ghc][wip/gc/nonmoving-nonconcurrent] 10 commits: rts: Fix CPP linter issues

Wed Jun 19 00:27:02 UTC 2019

Ben Gamari pushed to branch wip/gc/nonmoving-nonconcurrent at Glasgow Haskell Compiler / GHC

Commits:
65b27369 by Ben Gamari at 2019-06-19T00:19:15Z
rts: Fix CPP linter issues

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7da1fa16 by Ben Gamari at 2019-06-19T00:19:46Z
Merge branch 'wip/gc/misc-rts' into wip/gc/preparation

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5a95ef88 by Ömer Sinan Ağacan at 2019-06-19T00:20:04Z
rts/BlockAlloc: Allow aligned allocation requests

This implements support for block group allocations which are aligned to
an integral number of blocks.

This will be used by the nonmoving garbage collector, which uses the
block allocator to allocate the segments which back its heap. These
segments are a fixed number of blocks in size, with each segment being
aligned to the segment size boundary. This allows us to easily find the
segment metadata stored at the beginning of the segment.

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51239d98 by Ömer Sinan Ağacan at 2019-06-19T00:20:04Z
rts/StableName: Expose FOR_EACH_STABLE_NAME, freeSnEntry, SNT_size

These will be needed when we implement sweeping in the nonmoving
collector.

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f9d9abef by Ben Gamari at 2019-06-19T00:20:04Z
rts: Disable aggregate-return warnings from gcc

This warning is a bit of a relic; there is little reason to avoid
aggregate return values in 2019.

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ea668b0f by Ömer Sinan Ağacan at 2019-06-19T00:20:04Z
rts/Scav: Expose scavenging functions

To keep the non-moving collector nicely separated from the moving
collector its scavenging phase will live in another file,
`NonMovingScav.c`. However, it will need to use these functions so
let's expose them.

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d6b55a36 by Ben Gamari at 2019-06-19T00:20:04Z
rts: Introduce flag to enable the nonmoving old generation

This flag will enable the use of a non-moving oldest generation.

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6f55f04d by Ben Gamari at 2019-06-19T00:20:05Z
rts: Introduce debug flag for non-moving GC

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73e2b8db by Ömer Sinan Ağacan at 2019-06-19T00:20:05Z
rts: Non-concurrent mark and sweep

This implements the core heap structure and a serial mark/sweep
collector which can be used to manage the oldest-generation heap.
This is the first step towards a concurrent mark-and-sweep collector
aimed at low-latency applications.

The full design of the collector implemented here is described in detail
in a technical note

    B. Gamari. "A Concurrent Garbage Collector For the Glasgow Haskell
    Compiler" (2018)

The basic heap structure used in this design is heavily inspired by

    K. Ueno & A. Ohori. "A fully concurrent garbage collector for
    functional programs on multicore processors." /ACM SIGPLAN Notices/
    Vol. 51. No. 9 (presented by ICFP 2016)

This design is intended to allow both marking and sweeping
concurrent to execution of a multi-core mutator. Unlike the Ueno design,
which requires no global synchronization pauses, the collector
introduced here requires a stop-the-world pause at the beginning and end
of the mark phase.

To avoid heap fragmentation, the allocator consists of a number of
fixed-size /sub-allocators/. Each of these sub-allocators allocators into
its own set of /segments/, themselves allocated from the block
allocator. Each segment is broken into a set of fixed-size allocation
blocks (which back allocations) in addition to a bitmap (used to track
the liveness of blocks) and some additional metadata (used also used
to track liveness).

This heap structure enables collection via mark-and-sweep, which can be
performed concurrently via a snapshot-at-the-beginning scheme (although
concurrent collection is not implemented in this patch).

The mark queue is a fairly straightforward chunked-array structure.
The representation is a bit more verbose than a typical mark queue to
accomodate a combination of two features:

 * a mark FIFO, which improves the locality of marking, reducing one of
   the major overheads seen in mark/sweep allocators (see [1] for
   details)

 * the selector optimization and indirection shortcutting, which
   requires that we track where we found each reference to an object
   in case we need to update the reference at a later point (e.g. when
   we find that it is an indirection). See Note [Origin references in
   the nonmoving collector] (in `NonMovingMark.h`) for details.

Beyond this the mark/sweep is fairly run-of-the-mill.

[1] R. Garner, S.M. Blackburn, D. Frampton. "Effective Prefetch for
    Mark-Sweep Garbage Collection." ISMM 2007.

Co-Authored-By: Ben Gamari <ben at well-typed.com>

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01a98ff3 by Ben Gamari at 2019-06-19T00:20:05Z
testsuite: Add nonmoving WAY

This simply runs the compile_and_run tests with `-xn`, enabling the
nonmoving oldest generation.

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29 changed files:

- docs/users_guide/runtime_control.rst
- includes/rts/Flags.h
- includes/rts/storage/Block.h
- libraries/base/GHC/RTS/Flags.hsc
- rts/Capability.c
- rts/Capability.h
- rts/RtsFlags.c
- rts/RtsStartup.c
- rts/Schedule.c
- rts/Schedule.h
- rts/StableName.c
- rts/StableName.h
- rts/Trace.h
- rts/Weak.c
- rts/ghc.mk
- rts/sm/BlockAlloc.c
- rts/sm/Evac.c
- rts/sm/GC.c
- rts/sm/GC.h
- rts/sm/GCAux.c
- rts/sm/GCThread.h
- + rts/sm/NonMoving.c
- + rts/sm/NonMoving.h
- + rts/sm/NonMovingMark.c
- + rts/sm/NonMovingMark.h
- + rts/sm/NonMovingScav.c
- + rts/sm/NonMovingScav.h
- + rts/sm/NonMovingSweep.c
- + rts/sm/NonMovingSweep.h

The diff was not included because it is too large.

View it on GitLab: https://gitlab.haskell.org/ghc/ghc/compare/ca978cfdae456430f5fa1a9a5fa0920f2126ed17...01a98ff3ef62c10980b5845640b1529fd387af7d

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