A value that starts "1", "y", or "Y" enabled incremental mode
permanently (any value was allowed formerly), while a value that
starts "0", "n", or "N" causes incremental-mode requests to be
ignored.
When a major GC triggers finalization, another major
GC is scheduled immediately on the grounds that the
finalizer may release other values. That was important
at once time, but the finalization and weak-reference
implementation has improved to the point where the
extra ful GC no longer seems necessary or useful.
Originally, generation 1/2 was intended to delay major
collections when the heap is especially large. It doesn't
seem to be effective in that case, and it can slow down
minor GCs, so continue to use it only in incremental
mode (where it helps significantly with fragmentation).
At the completion of an incremental major GC, if incremental
mode wasn't requested recently, schedule an immediate major
GC to reduce the heap back to its normal footprint.
Also, make nursery 1/4 as big in incremental mode, and
correspondingly tune the amount of work to perform per
collection by 1/4 its old value. Using generation 1/2
reduces fragmentation that would otherwise be increase
by a smaller nursery.
The main intent of this change is to raise the buffer size
for ARM, but that would leave only 32-bit x86 at size 100, so
just make it size large for all machines.
Increemntal GC skips the old-generation compaction phase.
For most applications, that's ok, but it's possible for
fragmentation to get out of hand. Detect that situation
and fall back to non-incremental mode for one major GC.
Memory accounting is enabled on demand; if demand goes
away --- as approximated by no live custodians having
a limit or previously been queried for memory use ---
then stop accounting until demand resumes.
Fix the case that an old-generation finalizer ends up
on a modified page after all old-generation marking
is complete.
Also, make sure epehemerons are checked after previous
marking that may have left the stack empty.
The allocation strategy for immobile objects avoids some fragmentation
in non-incremental mode, but it interferes with finishing up an
incremental major collection, so trade some fragmentation for
an earlier finish (which is far more likely to use less memory
instead of more, despite extra fragmentation).
Really, just improve when majors GCs are forced to trigger
further finalizations. This improvement makes `(collect-garbage)`
followed by `(collect-garbage 'incremental)` move more
reliably into incremental mode.
When `(collect-garbage 'minor)` is combined with incremental
mode, do less incremental work. At the same time, don't
skip an incremental GC just because a major GC is ready.
Although calling `(collect-garbage 'incremental)` in a program with
a periodic task is the best way to request incremental collection, it's
handy for some experiments to have an environment variable that turns
it on permanently.
This change also makes incremental-mode minor collections log as "mIn"
instead of "min", and it changes the first field of the logged
`gc-info` structure to be a mode symbol instead of a boolean.
Incremental GC now works well enough to be useful for some programs
(e.g., games). Memory accounting is still not incremental, so DrRacket
(and running programs in DrRacket) does not really support incremental
collection, although pause times can be much shorter in incremental
mode than by default.
This step is semi-incremental, in that it can happen during
incremental collection, but all finalization is performed at once.
This will work well enoguh if the number of finalizers, weak boxes,
etc., will be small enough relative to the heap size.
Casting a `uintptr_t` to `double` seems not to round to
nearest, so keep all bits while moving to `double` and
use arithmetic to combine them (since the rounding mode
is used correctly for arithmetic).
The strategy of converting a bignum to a flonum by converting on word
boundaries can lose one bit of precision. (If the use of a word
boundary causes a single bit to get rounded away, but the first bit of
the next word is non-zero, then the rounding might have been down when
it should have been up.)
Avoid the problem by aligning relative to the high bit, instead.
Fix even basic readind when extflonums are not supported, but
also fix reading extflonums with large exponents (related to
the other recent changes to number parsing).
Allow a more dynamic (than `impersonator-prop:application-mark`)
determination of continuation marks and associated values to wrap the
call of an impersonated procedure.
When an internal-definition context is used with `local-expand`, the
any binding added to the context affect expansion, but the binding do
not appear in the expansion. As a result, Check Syntax was unable to
draw an arrow from the `s` use to its binding in
(class object%
(define-struct s ())
s)
The general solution is to add the internal-definition context's
bindings to the expansion as a 'disappeared-bindings property. The new
`internal-definitionc-context-track` function does that using a new
`internal-definition-context-binding-identifier` primitive.
Mishandling of the `require`-binding table could cause
`racket/private/pre-base` to export `andmap` as syntax, for example,
instead of as a variable. The syntax-versus-variable distinction
doesn't usually matter, but it affects the order of exports in
bytecode form.
Even though `dynamic-require` might lead to loading source, the
path into the compiler for that source will force compile-time code
as needed.
One benefit of ths change is that `racket -l pict3d` takes about half
as long, because `racket/gui` includes a `dynamic-require` to load a
platform-specific back-end, while `pict3d` can pull in a lot of
compile-time code to cooperate with Typed Racket.
Getting NULL from CTFontCollectionCreateMatchingFontDescriptors()
might indicate a font installation problem; I'm not sure. In any case,
checking for NULL avoids a crash on at least one installation.
This bug is already fixed in the Cairo source repo, so we
can discard the patch on the next Cairo upgrade.
It's not clear which platforms are affected. On OS X, at least,
writing to a global constant can cause a crash.
Thanks to Spencer for making a small example that triggers the bug
(added to the "draw-test" package).
The CTFontCreatePathForGlyph() function can return NULL when
the glyph exists but has an empty path. Instead of treating that
as failure, which causes Cairo to generate a bitmap version of
the glyph, check that the glyph is mapped for bounding boxes,
and treat a NULL path as an empty path in that case.
The `--enable-extflonums` option doesn't really do anything, since
extflonum support is enabled automtatically when the compiler's
configuration allows it. To make this slightly less confusing, report
an error when extflonums cannot be supported, despite
`--enable-extflonums`. The error is reported via compiling, instead of
via `configure`, but hopefully that's enough to be helpful.
Continuing with 2f25a1e2bd...
On further reflection, a GC is possible because a
thread swap is possible, and that's asking for trouble.
Disallow thread swaps (and, incidentally, GCs) whle
comparing scope propagations from the cache.
Merge to v6.3
Repairs a problem with d719c06e00.
A GC can happen while checking whether a cache entry matches,
in which case the cache is cleared, so don't check the cache
slot again after comparing.
Merge to v6.3
Repairs 3eb2c20ad0, which used a scope-set comparison for
a table that maps scopes to propagation actions (add, remove,
or flip).
Closes#1113
Merge to v6.3
In `syntax-local-lift-require`, avoid scope adjustments intended
to deal with `require` forms that are compiled in one namespace
and evaluated in another.
When `or` has many subexpressions, the expansion generates a
sequence of deeply nested `let`s, where original and macro-introduced
forms are interleaved in a way that defeats a minimal
child-is-same-as-parent sharing of scope sets. Add a small
cache that's good enough to capture extra sharing and
dramatically lower memory use for an `or` that has 1000
subexpressions.
When an import is shadowed by another import or by a definition, don't
include it in the set of bindings in the resut of
`syntax-local-module-required-identifiers` or in the set that can be
exported by `all-from-out`.
Merge to v6.3
To make the API consistent for MSVC versus MinGW builds, make
a functional formerly required for embedding on 32-bit Windows
always available and required for all Windows variants.
Recent versions of MinGW-W64 use emutls for `__thread` variables,
and that's much slower than Windows-native TLS. Go back to the
inline-assembly implementation of therad-local access.
Make the old-generation marking process incremental
on request, where `(collect-garbage 'incremental)`
makes a request.
Only the marking phase of an old-generation collection
is incremental, so far. In exchange for slower
minor collections and a larger heap, you get a major
collection pause time that is roughly halved. So, this
is a step forward, but not good enough for most purposes
that need incremental collection.
An incremental-mode request sticks until the next
major GC. The idea is that any program that could
benefit from incremental collection will have
some sort of periodic task where it can naturally
request incremental mode. (In particular, that
request belongs in the program, not in some external
flag to the runtime system.) Otherwise, the
system should revert to non-incremental mode, given
that incremental mode is slower overall and can
use much more memory --- usually within a factor of
two, but the factor can be much worse due to
fragmentation.
For a minor GC and pages that contain backpointers,
leave mark bits as they are; instead make a pass to
shift mark bits for new objects to "dead" bits, and
use dead bits for fixup.
This change is intended as a small step toward incremental
collection.
The rule for using generation 1/2is based on the current
memory use versus the maximum size of generation 0. Recent
changes to the GC have caused that size to vary during
a collection, which means that the choice to use generation
1/2 or not can change within a collection.
Partial use of generation 1/2 doesn't inherently cause problems, but
it can cause a generation-1 object to point to a generation-1/2 object
even though the former was allocated after the latter. That's a
problem on if getting generations out of order relative to allocation
order can create problems. As it happens, reset_finalizer_tree()
checks the generation of the finalization record and not the finalized
pointer, because the record is always allocated after the pointer.
Merge to v6.3
Certain datatypes in the runtime system are not supposed
to be hashed, where bits normally reserved for hash codes
are used for other purposes. A bad bytecode file can cause
some of those to be hashed, anyway. Normally, the damage is
isolated to that content of the damaged bytecode, but
certain variable-reference bytecode forms are both shared
and non-hashable. Set a bit that ensures hashing will not
change flags in the shared object.
This problem was exposed by fuzz testing.
When a compiler is run in standards mode, predefined macros that
do not start with "_" are dropped, so use the "_" versions
consistently. Whether or not Racket itself would compile in
standards mode, the Racket headers should be able to work that
way --- at least on Unix platforms.
In Mac OS X 10.11, something about the use of exceptions triggers
a libunwind stack traversal, and that traversal runs into trouble
with Racket's stack mangling for threads. Inserting generated code
in the stack frame sequence causes libunwind to give up and avoids
a crash (e.g., with `-j -l drracket` on startup).
After some expansions, a expression with the syntax property 'inferred-name of
'x is converted to one with ('x . 'x), so it's not useful to get the name of a
procedure. So we simplify the syntax property 'inferred-name to handle
these cases.
When a place message is deserialized by simply adopting the page
containing the message, the adoption can trigger a garbage
collection, but there's still a pointer to a chain of objects
"in flight" in the thread, and a GC can discard the pairs that
form the chain.
Removing all original module context doesn't work, because it
doesn't distinguish between fragments of syntax that had the
"inside-edge" scope without the "outside-edge" scope.
Record the presence of the outside-edge scope by using the
root scope, and convert the root scope to the current namespace's
outside-edge scope on evaluation.
The bug could cause
#lang racket/base
(define x 'outer)
(define-syntax-rule (def-and-use-m given-x)
(begin
(define-syntax-rule (m)
(let ()
(define given-x 'inner)
x))
(m)))
(def-and-use-m x)
to produce 'inner when it should produce 'outer.
Thanks to Brian Mastenbrook for pointing the problem and
providing examples.
Interrupting bytecode unmarshal for syntax objects could leave
half-constructed values in a table that is intended to resolve graph
structure. Clear out work towards a graph construction when
interrupted.
The most common symptom of half-constructed syntax objects was a crash
after a Ctl-C during startup.
