| Commit message (Collapse) | Author | Age | Files | Lines |
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is used outside of the rts so we do this rather than just fish it out of
the repo in ad-hoc way, in order to make packages in this repo more
self-contained.
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See #19357
The event reports the
* Current number of megablocks allocated
* The number that the RTS thinks it needs
* The number is managed to return to the OS
When current > need then the difference is returned to the OS, the
successful number of returned mblocks is reported by 'returned'.
In a fragmented heap current > need but returned < current - need.
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Block flags are very useful for determining the state of a block.
However, some block allocator users don't touch them, leading to
misleading values. Ensure that we zero then when zero-on-gc is set. This
is safe and makes the flags more useful during debugging.
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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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Zeros heap memory after gc freed it.
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Our new CPP linter enforces this.
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This brings in initial support for compact regions, as described in the
ICFP 2015 paper "Efficient Communication and Collection with Compact
Normal Forms" (Edward Z. Yang et.al.) and implemented by Giovanni
Campagna.
Some things may change before the 8.2 release, but I (Simon M.) wanted
to get the main patch committed so that we can iterate.
What documentation there is is in the Data.Compact module in the new
compact package. We'll need to extend and polish the documentation
before the release.
Test Plan:
validate
(new test cases included)
Reviewers: ezyang, simonmar, hvr, bgamari, austin
Subscribers: vikraman, Yuras, RyanGlScott, qnikst, mboes, facundominguez, rrnewton, thomie, erikd
Differential Revision: https://phabricator.haskell.org/D1264
GHC Trac Issues: #11493
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- Move the numaMap and nNumaNodes out of RtsFlags to Capability.c
- Add a test to tests/rts
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Summary:
The aim here is to reduce the number of remote memory accesses on
systems with a NUMA memory architecture, typically multi-socket servers.
Linux provides a NUMA API for doing two things:
* Allocating memory local to a particular node
* Binding a thread to a particular node
When given the +RTS --numa flag, the runtime will
* Determine the number of NUMA nodes (N) by querying the OS
* Assign capabilities to nodes, so cap C is on node C%N
* Bind worker threads on a capability to the correct node
* Keep a separate free lists in the block layer for each node
* Allocate the nursery for a capability from node-local memory
* Allocate blocks in the GC from node-local memory
For example, using nofib/parallel/queens on a 24-core 2-socket machine:
```
$ ./Main 15 +RTS -N24 -s -A64m
Total time 173.960s ( 7.467s elapsed)
$ ./Main 15 +RTS -N24 -s -A64m --numa
Total time 150.836s ( 6.423s elapsed)
```
The biggest win here is expected to be allocating from node-local
memory, so that means programs using a large -A value (as here).
According to perf, on this program the number of remote memory accesses
were reduced by more than 50% by using `--numa`.
Test Plan:
* validate
* There's a new flag --debug-numa=<n> that pretends to do NUMA without
actually making the OS calls, which is useful for testing the code
on non-NUMA systems.
* TODO: I need to add some unit tests
Reviewers: erikd, austin, rwbarton, ezyang, bgamari, hvr, niteria
Subscribers: thomie
Differential Revision: https://phabricator.haskell.org/D2199
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The `nat` type was an alias for `unsigned int` with a comment saying
it was at least 32 bits. We keep the typedef in case client code is
using it but mark it as deprecated.
Test Plan: Validated on Linux, OS X and Windows
Reviewers: simonmar, austin, thomie, hvr, bgamari, hsyl20
Differential Revision: https://phabricator.haskell.org/D2166
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- Rename to the (more correct) NUM_FREE_LISTS
- NUM_FREE_LISTS should be derived from the block and mblock sizes, not
defined manually. It was actually too large by one, which caused a
little bit of (benign) extra work in the form of a redundant loop
iteration in some cases.
- Add some ASSERTs for input preconditions to log_2() and log_2_ceil()
- Fix some comments
- Fix usage in allocLargeChunk, to account for the fact that
log_2_ceil() can return NUM_FREE_LISTS.
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This reverts commit 546f24e4f8a7c086b1e5afcdda624176610cbcf8.
And adds a fix for Windows: we need to use __builtin_clzll() rather than
__builtin_clzl(), because StgWord is unsigned long long on Windows.
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This reverts commit 24864ba5587c1a0447beabae90529e8bb4fa117a.
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A microoptimisation in the block allocator.
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Summary:
The current OS memory allocator conflates the concepts of allocating
address space and allocating memory, which makes the HEAP_ALLOCED()
implementation excessively complicated (as the only thing it cares
about is address space layout) and slow. Instead, what we want
is to allocate a single insanely large contiguous block of address
space (to make HEAP_ALLOCED() checks fast), and then commit subportions
of that in 1MB blocks as we did before.
This is currently behind a flag, USE_LARGE_ADDRESS_SPACE, that is only enabled for
certain OSes.
Test Plan: validate
Reviewers: simonmar, ezyang, austin
Subscribers: thomie, carter
Differential Revision: https://phabricator.haskell.org/D524
GHC Trac Issues: #9706
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Summary: Initialising the whole group is expensive and unnecessary.
Test Plan: validate
Reviewers: austin, bgamari, rwbarton
Subscribers: thomie
Differential Revision: https://phabricator.haskell.org/D1071
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This reverts commit 39b5c1cbd8950755de400933cecca7b8deb4ffcd.
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Signed-off-by: Austin Seipp <austin@well-typed.com>
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This will hopefully help ensure some basic consistency in the forward by
overriding buffer variables. In particular, it sets the wrap length, the
offset to 4, and turns off tabs.
Signed-off-by: Austin Seipp <austin@well-typed.com>
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Signed-off-by: Edward Z. Yang <ezyang@cs.stanford.edu>
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Signed-off-by: Edward Z. Yang <ezyang@cs.stanford.edu>
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Forcing large allocations here can creates serious fragmentation in
some cases, and since the large allocations are only a small
optimisation we should allow the nursery to hoover up small blocks
before allocating large chunks.
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lnat was originally "long unsigned int" but we were using it when we
wanted a 64-bit type on a 64-bit machine. This broke on Windows x64,
where long == int == 32 bits. Using types of unspecified size is bad,
but what we really wanted was a type with N bits on an N-bit machine.
StgWord is exactly that.
lnat was mentioned in some APIs that clients might be using
(e.g. StackOverflowHook()), so we leave it defined but with a comment
to say that it's deprecated.
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This patch makes two changes to the way stacks are managed:
1. The stack is now stored in a separate object from the TSO.
This means that it is easier to replace the stack object for a thread
when the stack overflows or underflows; we don't have to leave behind
the old TSO as an indirection any more. Consequently, we can remove
ThreadRelocated and deRefTSO(), which were a pain.
This is obviously the right thing, but the last time I tried to do it
it made performance worse. This time I seem to have cracked it.
2. Stacks are now represented as a chain of chunks, rather than
a single monolithic object.
The big advantage here is that individual chunks are marked clean or
dirty according to whether they contain pointers to the young
generation, and the GC can avoid traversing clean stack chunks during
a young-generation collection. This means that programs with deep
stacks will see a big saving in GC overhead when using the default GC
settings.
A secondary advantage is that there is much less copying involved as
the stack grows. Programs that quickly grow a deep stack will see big
improvements.
In some ways the implementation is simpler, as nothing special needs
to be done to reclaim stack as the stack shrinks (the GC just recovers
the dead stack chunks). On the other hand, we have to manage stack
underflow between chunks, so there's a new stack frame
(UNDERFLOW_FRAME), and we now have separate TSO and STACK objects.
The total amount of code is probably about the same as before.
There are new RTS flags:
-ki<size> Sets the initial thread stack size (default 1k) Egs: -ki4k -ki2m
-kc<size> Sets the stack chunk size (default 32k)
-kb<size> Sets the stack chunk buffer size (default 1k)
-ki was previously called just -k, and the old name is still accepted
for backwards compatibility. These new options are documented.
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as well as decommiting it.
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And add a comment about the dangers of int overflow
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The GC had a two-level structure, G generations each of T steps.
Steps are for aging within a generation, mostly to avoid premature
promotion.
Measurements show that more than 2 steps is almost never worthwhile,
and 1 step is usually worse than 2. In theory fractional steps are
possible, so the ideal number of steps is somewhere between 1 and 3.
GHC's default has always been 2.
We can implement 2 steps quite straightforwardly by having each block
point to the generation to which objects in that block should be
promoted, so blocks in the nursery point to generation 0, and blocks
in gen 0 point to gen 1, and so on.
This commit removes the explicit step structures, merging generations
with steps, thus simplifying a lot of code. Performance is
unaffected. The tunable number of steps is now gone, although it may
be replaced in the future by a way to tune the aging in generation 0.
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At the moment, this just saves a memory reference in the GC inner loop
(worth a percent or two of GC time). Later, it will hopefully let me
experiment with partial steps, and simplifying the generation/step
infrastructure.
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The first phase of this tidyup is focussed on the header files, and in
particular making sure we are exposinng publicly exactly what we need
to, and no more.
- Rts.h now includes everything that the RTS exposes publicly,
rather than a random subset of it.
- Most of the public header files have moved into subdirectories, and
many of them have been renamed. But clients should not need to
include any of the other headers directly, just #include the main
public headers: Rts.h, HsFFI.h, RtsAPI.h.
- All the headers needed for via-C compilation have moved into the
stg subdirectory, which is self-contained. Most of the headers for
the rest of the RTS APIs have moved into the rts subdirectory.
- I left MachDeps.h where it is, because it is so widely used in
Haskell code.
- I left a deprecated stub for RtsFlags.h in place. The flag
structures are now exposed by Rts.h.
- Various internal APIs are no longer exposed by public header files.
- Various bits of dead code and declarations have been removed
- More gcc warnings are turned on, and the RTS code is more
warning-clean.
- More source files #include "PosixSource.h", and hence only use
standard POSIX (1003.1c-1995) interfaces.
There is a lot more tidying up still to do, this is just the first
pass. I also intend to standardise the names for external RTS APIs
(e.g use the rts_ prefix consistently), and declare the internal APIs
as hidden for shared libraries.
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