numa - aware allocation in zig

numa_pages.zig

const std = @import("std");
const posix = std.posix;
const numaif = @cImport({
  @cInclude("numaif.h");
  @cInclude("errno.h");
});

extern threadlocal var errno: c_int;

fn numa_alloc(size: usize, node: ?u1) ![]align(std.mem.page_size) u8 {
    const hint = @atomicLoad(@TypeOf(std.heap.next_mmap_addr_hint), &std.heap.next_mmap_addr_hint, .unordered);
    const slice = try posix.mmap(
        hint,
        size,
        posix.PROT.READ | posix.PROT.WRITE,
        .{ .TYPE = .PRIVATE, .ANONYMOUS = true },
        -1,
        0,
    );
    errdefer posix.munmap(slice);

    const nodemask = @as(u64, 1) << node.?;
    const mbind_result = numaif.mbind(slice.ptr, size, numaif.MPOL_BIND, &nodemask, 2, 0);
    const Binderror = enum {FAULT, INVAL, IO, NOMEM, EPERM};

    if (mbind_result != 0) {
       const err: Binderror = switch (errno) {
          numaif.EFAULT => .FAULT,
          numaif.EINVAL => .INVAL,
          numaif.EIO => .IO,
          numaif.ENOMEM => .NOMEM,
          numaif.EPERM => .EPERM,
          else => {
             std.debug.print("error {}\n", .{errno});
             return error.mbind_fail;
          }
       };
       std.debug.print("bind failed with: {}\n", .{err});
       return error.mbind_fail;
    } else {
       return slice;
    }
} 

fn numa_free(slice: []align(std.mem.page_size) u8) void {
    posix.munmap(slice);
}

pub fn main() !void {
   const mem1 = try numa_alloc(4096, 0);
   std.debug.print("mem1: {*}\n", .{mem1});
   numa_free(mem1);

   const mem2 = try numa_alloc(4096, 1);
   std.debug.print("mem2: {*}\n", .{mem2});
   numa_free(mem2);
}

run:

isaac@andoria-08:~$ zig run -lc -lnuma test.zig
mem1: u8@7f2b0be69000
bind failed with: test.numa_alloc.Binderror.INVAL
error: mbind_fail
/home/isaac/test.zig:39:8: 0x1032cff in numa_alloc (test)
      return error.mbind_fail; 
      ^
/home/isaac/test.zig:54:17: 0x10339fa in main (test)
  const mem2 = try numa_alloc(4096, 1);