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std.heap.SmpAllocator: implement searching on alloc

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rotate a couple times before resorting to mapping more memory.
This commit is contained in:
Andrew Kelley
2025-02-06 19:48:02 -08:00
parent 7360be19a4
commit 60765a9ee2
1 changed files with 48 additions and 21 deletions
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69
lib/std/heap/SmpAllocator.zig
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@@ -158,27 +158,53 @@ fn alloc(context: *anyopaque, len: usize, alignment: mem.Alignment, ra: usize) ?
return PageAllocator.map(len, alignment);
}
const t = Thread.lock();
defer t.unlock();
const slot_size = slotSize(class);
const max_search = 2;
var search_count: u32 = 0;
const top_free_ptr = t.frees[class];
if (top_free_ptr != 0) {
const node: *usize = @ptrFromInt(top_free_ptr + (slot_size - @sizeOf(usize)));
t.frees[class] = node.*;
return @ptrFromInt(top_free_ptr);
var t = Thread.lock();
outer: while (true) {
const top_free_ptr = t.frees[class];
if (top_free_ptr != 0) {
@branchHint(.likely);
defer t.unlock();
const node: *usize = @ptrFromInt(top_free_ptr + (slot_size - @sizeOf(usize)));
t.frees[class] = node.*;
return @ptrFromInt(top_free_ptr);
}
const next_addr = t.next_addrs[class];
if ((next_addr % slab_len) != 0) {
@branchHint(.likely);
defer t.unlock();
t.next_addrs[class] = next_addr + slot_size;
return @ptrFromInt(next_addr);
}
if (search_count >= max_search) {
@branchHint(.likely);
defer t.unlock();
const slab = PageAllocator.map(slab_len, .fromByteUnits(std.heap.pageSize())) orelse return null;
t.next_addrs[class] = @intFromPtr(slab) + slot_size;
return slab;
}
t.unlock();
t = undefined;
const cpu_count = global.cpu_count;
assert(cpu_count != 0);
var index = thread_id.toIndex();
while (true) {
index = (index + 1) % cpu_count;
t = &global.threads[index];
if (t.mutex.tryLock()) {
thread_id = .fromIndex(index);
search_count += 1;
continue :outer;
}
}
}
const next_addr = t.next_addrs[class];
if (next_addr % slab_len == 0) {
const slab = PageAllocator.map(slab_len, .fromByteUnits(std.heap.pageSize())) orelse return null;
t.next_addrs[class] = @intFromPtr(slab) + slot_size;
return slab;
}
t.next_addrs[class] = next_addr + slot_size;
return @ptrFromInt(next_addr);
}
fn resize(context: *anyopaque, memory: []u8, alignment: mem.Alignment, new_len: usize, ra: usize) bool {
@@ -214,12 +240,13 @@ fn free(context: *anyopaque, memory: []u8, alignment: mem.Alignment, ra: usize)
return PageAllocator.unmap(@alignCast(memory));
}
const t = Thread.lock();
defer t.unlock();
const slot_size = slotSize(class);
const addr = @intFromPtr(memory.ptr);
const node: *usize = @ptrFromInt(addr + (slot_size - @sizeOf(usize)));
const t = Thread.lock();
defer t.unlock();
node.* = t.frees[class];
t.frees[class] = addr;
}