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QRingBuffer: cache the last released block

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A typical ring buffer usage is a sequence of reserve()->chop()->read()
cycles. Usually, between these cycles, the buffer doesn't contain data and
all blocks are released. To reduce reallocations, keep the most recently
used block while the buffer is empty.

Change-Id: I8128f1f04649ae005fd0a480f17f95de01a9a135
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@theqtcompany.com>
This commit is contained in:
Alex Trotsenko 2014-11-28 10:58:49 +02:00
parent bb4625f472
commit e06f4c2558
1 changed files with 26 additions and 8 deletions
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34
src/corelib/tools/qringbuffer_p.h
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@ -91,11 +91,20 @@ public:
int blockSize = buffers.first().size() - head;
if (tailBuffer == 0 || blockSize > bytes) {
bufferSize -= bytes;
if (bufferSize <= 0)
clear(); // try to minify/squeeze us
else
// keep a single block around if it does not exceed
// the basic block size, to avoid repeated allocations
// between uses of the buffer
if (bufferSize <= bytes) {
if (buffers.first().size() <= basicBlockSize) {
bufferSize = 0;
head = tail = 0;
} else {
clear(); // try to minify/squeeze us
}
} else {
head += bytes;
bufferSize -= bytes;
}
return;
}
@ -139,11 +148,20 @@ public:
inline void chop(int bytes) {
while (bytes > 0) {
if (tailBuffer == 0 || tail > bytes) {
bufferSize -= bytes;
if (bufferSize <= 0)
clear(); // try to minify/squeeze us
else
// keep a single block around if it does not exceed
// the basic block size, to avoid repeated allocations
// between uses of the buffer
if (bufferSize <= bytes) {
if (buffers.first().size() <= basicBlockSize) {
bufferSize = 0;
head = tail = 0;
} else {
clear(); // try to minify/squeeze us
}
} else {
tail -= bytes;
bufferSize -= bytes;
}
return;
}