From 7eed57511a786861b513af089aef48651fed7891 Mon Sep 17 00:00:00 2001 From: Andrei Golubev Date: Thu, 29 Oct 2020 14:25:48 +0100 Subject: QArrayDataPointer: redesign (and simplify) growth policy It looks like we can drastically simplify the way QADP grows without sacrificing much: 1. append-only use cases should have the same performance as before 2. prepend-only use cases should (with the help of other commits) get additional performance speedup 3. mid-insertion is harder to reason about, but it is either unchanged or benefits a bit as there's some free space at both ends now 4. mixed prepend/append cases are weird and would keep excess free space around but this is less critical and overall less used AFAIK Now, QList would actually start to feel like a double-ended container instead of "it's QVector but with faster prepend". This commit should help close the performance gap between 6.0 and 5.15 as well As a drawback, we will most likely have more space allocated in mixed and mid-insert cases. This needs to be checked Task-number: QTBUG-86583 Change-Id: I7c6ede896144920fe01862b9fe789c8fdfc11f80 Reviewed-by: Lars Knoll Reviewed-by: Thiago Macieira --- .../corelib/tools/qarraydata/tst_qarraydata.cpp | 22 +++++++++++++++------- 1 file changed, 15 insertions(+), 7 deletions(-) (limited to 'tests/auto/corelib/tools/qarraydata/tst_qarraydata.cpp') diff --git a/tests/auto/corelib/tools/qarraydata/tst_qarraydata.cpp b/tests/auto/corelib/tools/qarraydata/tst_qarraydata.cpp index 4c520d0eaa..b7d07f836e 100644 --- a/tests/auto/corelib/tools/qarraydata/tst_qarraydata.cpp +++ b/tests/auto/corelib/tools/qarraydata/tst_qarraydata.cpp @@ -2094,6 +2094,7 @@ void tst_QArrayData::dataPointerAllocate() using DataPointer = QArrayDataPointer; auto oldDataPointer = createDataPointer(capacity, initValue); + oldDataPointer->insert(oldDataPointer.begin(), 1, initValue); oldDataPointer->insert(oldDataPointer.begin(), 1, initValue); // trigger prepend QVERIFY(!oldDataPointer.needsDetach()); @@ -2105,11 +2106,14 @@ void tst_QArrayData::dataPointerAllocate() QVERIFY(newAlloc > oldDataPointer.constAllocatedCapacity()); QCOMPARE(freeAtBegin + freeAtEnd, newAlloc); - // when not detached, the behavior is the same as of ::realloc - if (allocationOptions & (QArrayData::GrowsForward | QArrayData::GrowsBackwards)) + if (allocationOptions & QArrayData::GrowsBackwards) { + // bad check, but will suffice for now, hopefully + QCOMPARE(freeAtBegin, (newAlloc - newSize) / 2); + } else if (allocationOptions & QArrayData::GrowsForward) { QCOMPARE(freeAtBegin, oldDataPointer.freeSpaceAtBegin()); - else + } else { QCOMPARE(freeAtBegin, 0); + } }; for (size_t n : {10, 512, 1000}) { @@ -2186,14 +2190,18 @@ void tst_QArrayData::dataPointerAllocateAlignedWithReallocate() QVERIFY(a.freeSpaceAtBegin() == 0); } QCOMPARE(a.freeSpaceAtBegin(), b.freeSpaceAtBegin()); + const auto oldSpaceAtBeginA = a.freeSpaceAtBegin(); a->reallocate(100, newFlags); b = QArrayDataPointer::allocateGrow(b, 100, b.size, newFlags); - // It is enough to test that the behavior of reallocate is the same as the - // behavior of allocate w.r.t. pointer adjustment in case of - // GrowsBackwards. Actual values are not that interesting - QCOMPARE(a.freeSpaceAtBegin(), b.freeSpaceAtBegin()); + // NB: when growing backwards, the behavior is not aligned + if (!(newFlags & QArrayData::GrowsBackwards)) { + QCOMPARE(a.freeSpaceAtBegin(), b.freeSpaceAtBegin()); + } else { + QCOMPARE(a.freeSpaceAtBegin(), oldSpaceAtBeginA); + QCOMPARE(b.freeSpaceAtBegin(), b.constAllocatedCapacity() / 2); + } } #ifndef QT_NO_EXCEPTIONS -- cgit v1.2.3