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Improve MemArena to only do a large alloc if it doesn't fit in the current block.

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This commit is contained in:
Nathan Vegdahl 2017-04-10 00:25:10 -07:00
parent d3b3a50a4d
commit 66eb01947f
1 changed files with 26 additions and 20 deletions
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30
mem_arena/src/lib.rs
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@ -132,18 +132,7 @@ impl MemArena {
if size == 0 {
return blocks.first_mut().unwrap().as_mut_ptr();
}
// If the desired size is considered a "large allocation", give it its own memory block.
else if size > self.large_alloc_threshold {
blocks.push(Vec::with_capacity(size + alignment - 1));
blocks.last_mut().unwrap().set_len(size + alignment - 1);
let start_index = alignment_offset(blocks.last().unwrap().as_ptr() as usize, alignment);
let block_ptr = blocks.last_mut().unwrap().as_mut_ptr();
return block_ptr.offset(start_index as isize);
}
// If the desired size is not a "large allocation", try to fit it into the current
// block, and only create a new block if doesn't fit.
// If it's non-zero-size.
else {
let start_index = {
let block_addr = blocks.first().unwrap().as_ptr() as usize;
@ -153,6 +142,7 @@ impl MemArena {
// If it will fit in the current block, use the current block.
if (start_index + size) <= blocks.first().unwrap().capacity() {
println!("In-Block, alloc size: {}", size);
blocks.first_mut().unwrap().set_len(start_index + size);
let block_ptr = blocks.first_mut().unwrap().as_mut_ptr();
@ -160,6 +150,21 @@ impl MemArena {
}
// If it won't fit in the current block, create a new block and use that.
else {
// If it's a "large allocation", give it its own memory block.
if size > self.large_alloc_threshold {
println!("Large Allocation, alloc size: {}", size);
blocks.push(Vec::with_capacity(size + alignment - 1));
blocks.last_mut().unwrap().set_len(size + alignment - 1);
let start_index = alignment_offset(blocks.last().unwrap().as_ptr() as usize,
alignment);
let block_ptr = blocks.last_mut().unwrap().as_mut_ptr();
return block_ptr.offset(start_index as isize);
}
// Otherwise create a new shared block.
else {
println!("New Block, alloc size: {}", size);
blocks.push(Vec::with_capacity(self.block_size));
let block_count = blocks.len();
blocks.swap(0, block_count - 1);
@ -174,4 +179,5 @@ impl MemArena {
}
}
}
}
}