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Loïc Grégoire
2026-10-07 18:03:06 -04:00
parent 6cd9117a05
commit 619c373d47
78 changed files with 1676 additions and 1118 deletions
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src/ex/vmem.zig
+55 -42
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@@ -1,13 +1,17 @@
//! Generic resource allocator, based on the vmem allocator described in:
//! Jeff Bonwick and Jonathan Adams'
//! "Magazines and Vmem: Extending the Slab Allocator to Many CPUs and Arbitrary Resources"
const std = @import("std");
//! "Magazines and Vmem: Extending the Slab Allocator to Many CPUs and
//! Arbitrary Resources"
const rtl = @import("rtl");
const r = @import("root");
const mm = r.mm;
const mmp = mm.private;
const ke = r.ke;
const std = @import("std");
const assert = std.debug.assert;
pub const Policy = enum {
/// Use the smallest free segment that can satisfy the request.
/// This tends to minimize fragmentation.
@@ -37,9 +41,9 @@ const Segment = struct {
};
const Linkage = union {
/// Linkage into a freelist, valid when type == .Free
/// Linkage into a freelist, valid when .Free
free_link: rtl.List.Entry,
/// Linkage into the allocated segments tree, valid when type == .Allocated
/// Linkage into the allocated segments tree, valid when .Allocated
tree_link: rtl.bst.Node,
};
/// The type of the segment.
@@ -80,6 +84,8 @@ const max_qcaches = 16;
var seg_zone: mmp.zone.TypedZone(Segment) = undefined;
const SegmentTree = rtl.RBTree(Segment.cmp);
pub const Arena = struct {
/// Name of the arena, for debugging purposes.
name: []const u8,
@@ -90,7 +96,7 @@ pub const Arena = struct {
/// Power of two freelists for free segments, indexed by log2(size).
freelists: [freelist_count]rtl.List,
/// Tree for allocated segments, indexed by base address.
allocated_segments: rtl.RBTree(Segment.cmp),
allocated_segments: SegmentTree,
/// Last segment allocated from, for NextFit policy.
rotor: ?*Segment,
/// Maximum size (**in bytes**) to do quantum caching on.
@@ -105,14 +111,12 @@ pub const Arena = struct {
lock: ke.Mutex,
const Self = @This();
const Span = struct { addr: usize, size: usize };
const Source = struct {
arena: *Self,
import: *const fn (*Self, usize, opts: AllocOptions) mm.Error!usize,
release: *const fn (*Self, addr: usize, size: usize) void,
arena: *Arena,
import: *const fn (*Arena, usize, opts: AllocOptions) mm.Error!usize,
release: *const fn (*Arena, addr: usize, size: usize) void,
};
const InitOptions = struct {
@@ -124,7 +128,7 @@ pub const Arena = struct {
/// Initialize the area for use.
pub fn init(
self: *Self,
self: *Arena,
name: []const u8,
opts: InitOptions,
) !void {
@@ -142,7 +146,11 @@ pub const Arena = struct {
self.qshift = std.math.log2_int(usize, self.quantum);
if (opts.span == null) {
rtl.assert(opts.source != null, "Arena init: null span without source", .{});
rtl.assert(
opts.source != null,
"Arena init: null span without source",
.{},
);
}
self.list.init();
@@ -170,7 +178,7 @@ pub const Arena = struct {
self.lock = ke.Mutex.init("arena");
self.allocated_segments = .init();
self.allocated_segments = SegmentTree.init();
self.rotor = null;
// Add initial span.
@@ -179,7 +187,7 @@ pub const Arena = struct {
}
}
pub fn deinit(self: *Self) void {
pub fn deinit(self: *Arena) void {
// Free all segments in the segment list
var entry = self.list.first();
while (entry != &self.list.head) {
@@ -191,12 +199,12 @@ pub const Arena = struct {
}
/// Add a span of memory to the arena.
pub fn add(self: *Self, span: Span) !void {
pub fn add(self: *Arena, span: Span) !void {
return self.add_opts(span, .Span);
}
/// Add a span of memory to the arena.
fn add_opts(self: *Self, span: Span, kind: Segment.Type) mm.Error!void {
fn add_opts(self: *Arena, span: Span, kind: Segment.Type) mm.Error!void {
const new_free_seg = try self.alloc_segment();
new_free_seg.* = Segment{
@@ -226,12 +234,15 @@ pub const Arena = struct {
/// Allocate a segment of memory from the arena.
/// Options:
/// - policy: allocation policy to use. Default is .InstantFit.
/// - alignment: if specified, the returned segment will be aligned to this boundary.
/// - min: if specified, the returned segment will be at least on this address.
/// - max: if specified, the returned segment will be at most on this address.
/// - alignment: if specified, the returned segment will be aligned to
/// this boundary.
/// - min: if specified, the returned segment will be at least on this
/// address.
/// - max: if specified, the returned segment will be at most on this
/// address.
/// Returns the base address of the allocated segment.
pub fn alloc(
self: *Self,
self: *Arena,
size: usize,
options: AllocOptions,
) mm.Error!usize {
@@ -252,7 +263,7 @@ pub const Arena = struct {
}
fn alloc_impl(
self: *Self,
self: *Arena,
size: usize,
options: AllocOptions,
) mm.Error!usize {
@@ -263,20 +274,20 @@ pub const Arena = struct {
.NextFit => self.next_fit(size, options),
};
if (ret != null) break :blk ret.?;
if (ret != null) break :blk ret orelse unreachable;
if (ret == null) {
try self.import(size, options);
}
// This is guaranteed to terminate eventually, either when the import
// brings in new free memory, or when it runs out.
// This is guaranteed to terminate eventually, either when
// the import brings in new free memory, or when it runs out.
};
const start, var seg = result;
std.debug.assert(seg.type == .Free);
std.debug.assert(seg.size >= size);
assert(seg.type == .Free);
assert(seg.size >= size);
// Remove the segment from the freelist.
self.remove_segment_from_freelist(seg);
@@ -303,11 +314,13 @@ pub const Arena = struct {
self.add_segment_to_freelist(left_seg);
}
// right split: seg is larger than needed, so split into allocated + free remainder.
// right split: seg is larger than needed, so split into alloc + free
// remainder.
// e.g. seg=[0x100, 0x10000], size=0x1000:
// before: [0x100, 0x10000] being processed
// after: [0x100, 0x1100] allocated, [0x1100, 0x10000] free
// the quantum check avoids creating a remainder too small to ever be useful.
// the quantum check avoids creating a remainder too small to ever be
// useful.
if (seg.size != size and (seg.size - size) > self.quantum - 1) {
const new_seg = try self.alloc_segment();
new_seg.* = .{
@@ -345,7 +358,7 @@ pub const Arena = struct {
}
/// Try to import memory from the parent arena.
fn import(self: *Self, size: usize, options: AllocOptions) mm.Error!void {
fn import(self: *Arena, size: usize, options: AllocOptions) mm.Error!void {
const src = self.source orelse return error.OutOfMemory;
// Ensure no funny stuff happens wrt the lock.
@@ -362,7 +375,7 @@ pub const Arena = struct {
);
}
pub fn free(self: *Self, addr: usize, size: usize) void {
pub fn free(self: *Arena, addr: usize, size: usize) void {
if (size <= self.qcache_max) {
const i = size >> self.qshift;
self.qcaches[i - 1].free(@ptrFromInt(addr));
@@ -375,7 +388,7 @@ pub const Arena = struct {
return self.free_impl(addr, size);
}
fn free_impl(self: *Self, addr: usize, size: usize) void {
fn free_impl(self: *Arena, addr: usize, size: usize) void {
// Find the allocated segment containing addr.
var search_node = Segment{
@@ -449,7 +462,7 @@ pub const Arena = struct {
}
/// Try to release a segment back to its source.
fn release(self: *Self, seg: *Segment) bool {
fn release(self: *Arena, seg: *Segment) bool {
const prev_entry = seg.link.prev;
if (prev_entry == &self.list.head) {
@@ -479,7 +492,7 @@ pub const Arena = struct {
// Implementation for the instant fit policy.
fn instant_fit(
self: *Self,
self: *Arena,
size: usize,
options: AllocOptions,
) ?struct { usize, *Segment } {
@@ -506,7 +519,7 @@ pub const Arena = struct {
// something in the lower freelist, so check there.
// This is O(n) but should happen very rarely.
if (!is_pow2) {
std.debug.assert(orig_idx != 0);
assert(orig_idx != 0);
var it = self.freelists[orig_idx].iterator();
while (it.next()) : (it.advance()) {
@@ -522,7 +535,7 @@ pub const Arena = struct {
// Implementation for the best fit policy.
// Find the smallest segment that can satisfy the request.
fn best_fit(
self: *Self,
self: *Arena,
size: usize,
options: AllocOptions,
) ?struct { usize, *Segment } {
@@ -552,7 +565,7 @@ pub const Arena = struct {
// Continue searching from the last allocated segment, wrapping around at
// the end of the arena.
fn next_fit(
self: *Self,
self: *Arena,
size: usize,
options: AllocOptions,
) ?struct { usize, *Segment } {
@@ -588,7 +601,7 @@ pub const Arena = struct {
// Try to fit the given segment to the request with the given options.
// Returns the fitted address if successful.
fn try_to_fit(
self: *Self,
self: *Arena,
segment: *const Segment,
size: usize,
options: AllocOptions,
@@ -610,22 +623,22 @@ pub const Arena = struct {
return null;
}
fn alloc_segment(self: *Self) !*Segment {
fn alloc_segment(self: *Arena) !*Segment {
_ = self;
return seg_zone.create();
}
fn free_segment(self: *Self, segment: *Segment) void {
fn free_segment(self: *Arena, segment: *Segment) void {
seg_zone.destroy(segment);
_ = self;
}
fn add_segment_to_freelist(self: *Self, segment: *Segment) void {
fn add_segment_to_freelist(self: *Arena, segment: *Segment) void {
const freelist = self.freelist_for_size(segment.size);
freelist.insert_tail(&segment.linkage.free_link);
}
fn remove_segment_from_freelist(self: *Self, segment: *Segment) void {
fn remove_segment_from_freelist(self: *Arena, segment: *Segment) void {
_ = self;
segment.linkage.free_link.remove();
}
@@ -634,7 +647,7 @@ pub const Arena = struct {
return std.math.log2_int(usize, size);
}
inline fn freelist_for_size(self: *Self, size: usize) *rtl.List {
inline fn freelist_for_size(self: *Arena, size: usize) *rtl.List {
return &self.freelists[freelist_index(size)];
}
};