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Set capacity to the target size when using realloc.
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@deadalnix
deadalnix committed Sep 2, 2023
1 parent 4616830 commit d8e9c0a
Showing 1 changed file with 8 additions and 10 deletions.
18 changes: 8 additions & 10 deletions sdlib/d/gc/tcache.d
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Original file line number Diff line number Diff line change
Expand Up @@ -97,16 +97,15 @@ public:
copySize = getSizeFromClass(oldSizeClass);
}
} else {
import d.gc.util;
copySize = min(size, pd.extent.usedCapacity);

auto esize = pd.extent.size;
if (samePointerness && alignUp(size, PageSize) == esize) {
pd.extent.setUsedCapacity(copySize);
pd.extent.setUsedCapacity(size);
return ptr;
}

// TODO: Try to extend/shrink in place.
import d.gc.util;
copySize = min(size, pd.extent.usedCapacity);
}

auto newPtr = alloc(size, containsPointers);
Expand All @@ -116,7 +115,7 @@ public:

if (isLargeSize(size)) {
auto npd = getPageDescriptor(newPtr);
npd.extent.setUsedCapacity(copySize);
npd.extent.setUsedCapacity(size);
}

memcpy(newPtr, ptr, copySize);
Expand Down Expand Up @@ -433,22 +432,21 @@ unittest getCapacity {
assert(threadCache.getCapacity(p2[0 .. 20000]) == 0);
assert(threadCache.getCapacity(p2[0 .. 20001]) == 0);

// Increasing the size of the allocation
// does not necesserly increase capacity.
// Increasing the size of the allocation increases capacity.
auto p3 = threadCache.realloc(p2, 20001, false);
assert(p3 is p2);

assert(threadCache.getCapacity(p3[0 .. 19999]) == 20480);
assert(threadCache.getCapacity(p3[0 .. 19999]) == 0);
assert(threadCache.getCapacity(p3[0 .. 20000]) == 0);
assert(threadCache.getCapacity(p3[0 .. 20001]) == 0);
assert(threadCache.getCapacity(p3[0 .. 20001]) == 20480);

auto p4 = threadCache.realloc(p3, 16000, false);
assert(p4 !is p3);
assert(threadCache.getCapacity(p4[0 .. 16000]) == 16384);

auto p5 = threadCache.realloc(p4, 20000, false);
assert(p5 !is p4);
assert(threadCache.getCapacity(p5[0 .. 16000]) == 20480);
assert(threadCache.getCapacity(p5[0 .. 20000]) == 20480);
}

unittest extend {
Expand Down

1 comment on commit d8e9c0a

@dsm9000
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@dsm9000 dsm9000 commented on d8e9c0a Sep 4, 2023 •
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Why would you increase the used capacity of an alloc without going through extend() ?
Reallocing upwards should only change the available spare capacity, not the used capacity.
This change breaks the expected logic of the whole thing!

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