Proposal for Direct-X-Buffer change to improve allocation of zero capacity buffers
Jon V.
sybersnake at gmail.com
Mon Aug 1 04:24:45 UTC 2016
The Direct Buffer does not optimize the allocation of zero capacity
buffers. I am proposing a simple if( cap != 0 ) condition that will
bypass most of the setup process.
Here is the current constructor:
Direct$Type$Buffer$RW$(int cap) { // package-private
#if[rw]
super(-1, 0, cap, cap);
boolean pa = VM.isDirectMemoryPageAligned();
int ps = Bits.pageSize();
long size = Math.max(1L, (long)cap + (pa ? ps : 0));
Bits.reserveMemory(size, cap);
long base = 0;
try {
base = unsafe.allocateMemory(size);
} catch (OutOfMemoryError x) {
Bits.unreserveMemory(size, cap);
throw x;
}
unsafe.setMemory(base, size, (byte) 0);
if (pa && (base % ps != 0)) {
// Round up to page boundary
address = base + ps - (base & (ps - 1));
} else {
address = base;
}
cleaner = Cleaner.create(this, new Deallocator(base, size, cap));
att = null;
#else[rw]
super(cap);
#end[rw]
}
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