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std.heap.SmpAllocator: simplify by putting freelist node at start

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This commit is contained in:
Andrew Kelley 2025-02-07 00:58:01 -08:00
parent 1ffae59fec
commit 88e2e60e88
1 changed files with 5 additions and 10 deletions
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15
lib/std/heap/SmpAllocator.zig
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@ -51,7 +51,7 @@ threadlocal var thread_index: u32 = 0;
const max_thread_count = 128;
const slab_len: usize = @max(std.heap.page_size_max, 256 * 1024);
/// Because of storing free list pointers, the minimum size class is 3.
const min_class = math.log2(math.ceilPowerOfTwoAssert(usize, 1 + @sizeOf(usize)));
const min_class = math.log2(@sizeOf(usize));
const size_class_count = math.log2(slab_len) - min_class;
const Thread = struct {
@ -132,7 +132,7 @@ fn alloc(context: *anyopaque, len: usize, alignment: mem.Alignment, ra: usize) ?
if (top_free_ptr != 0) {
@branchHint(.likely);
defer t.unlock();
const node: *usize = @ptrFromInt(top_free_ptr + (slot_size - @sizeOf(usize)));
const node: *usize = @ptrFromInt(top_free_ptr);
t.frees[class] = node.*;
return @ptrFromInt(top_free_ptr);
}
@ -202,22 +202,17 @@ fn free(context: *anyopaque, memory: []u8, alignment: mem.Alignment, ra: usize)
return PageAllocator.unmap(@alignCast(memory));
}
const slot_size = slotSize(class);
const addr = @intFromPtr(memory.ptr);
const node: *usize = @ptrFromInt(addr + (slot_size - @sizeOf(usize)));
const node: *usize = @alignCast(@ptrCast(memory.ptr));
const t = Thread.lock();
defer t.unlock();
node.* = t.frees[class];
t.frees[class] = addr;
t.frees[class] = @intFromPtr(node);
}
fn sizeClassIndex(len: usize, alignment: mem.Alignment) usize {
return @max(
@bitSizeOf(usize) - @clz(len + (@sizeOf(usize) - 1)),
@intFromEnum(alignment) + 1,
) - min_class;
return @max(@bitSizeOf(usize) - @clz(len - 1), @intFromEnum(alignment), min_class) - min_class;
}
fn slotSize(class: usize) usize {