io_uring: allow user configurable IO thread CPU affinity
io-wq defaults to per-node masks for IO workers. This works fine by
default, but isn't particularly handy for workloads that prefer more
specific affinities, for either performance or isolation reasons.
This adds IORING_REGISTER_IOWQ_AFF that allows the user to pass in a CPU
mask that is then applied to IO thread workers, and an
IORING_UNREGISTER_IOWQ_AFF that simply resets the masks back to the
default of per-node.
Note that no care is given to existing IO threads, they will need to go
through a reschedule before the affinity is correct if they are already
running or sleeping.
Signed-off-by: Jens Axboe <axboe@kernel.dk>
diff --git a/fs/io_uring.c b/fs/io_uring.c
index d916eb2..46a25a7 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -9983,6 +9983,43 @@ static int io_register_rsrc(struct io_ring_ctx *ctx, void __user *arg,
return -EINVAL;
}
+static int io_register_iowq_aff(struct io_ring_ctx *ctx, void __user *arg,
+ unsigned len)
+{
+ struct io_uring_task *tctx = current->io_uring;
+ cpumask_var_t new_mask;
+ int ret;
+
+ if (!tctx || !tctx->io_wq)
+ return -EINVAL;
+
+ if (!alloc_cpumask_var(&new_mask, GFP_KERNEL))
+ return -ENOMEM;
+
+ cpumask_clear(new_mask);
+ if (len > cpumask_size())
+ len = cpumask_size();
+
+ if (copy_from_user(new_mask, arg, len)) {
+ free_cpumask_var(new_mask);
+ return -EFAULT;
+ }
+
+ ret = io_wq_cpu_affinity(tctx->io_wq, new_mask);
+ free_cpumask_var(new_mask);
+ return ret;
+}
+
+static int io_unregister_iowq_aff(struct io_ring_ctx *ctx)
+{
+ struct io_uring_task *tctx = current->io_uring;
+
+ if (!tctx || !tctx->io_wq)
+ return -EINVAL;
+
+ return io_wq_cpu_affinity(tctx->io_wq, NULL);
+}
+
static bool io_register_op_must_quiesce(int op)
{
switch (op) {
@@ -9998,6 +10035,8 @@ static bool io_register_op_must_quiesce(int op)
case IORING_REGISTER_FILES_UPDATE2:
case IORING_REGISTER_BUFFERS2:
case IORING_REGISTER_BUFFERS_UPDATE:
+ case IORING_REGISTER_IOWQ_AFF:
+ case IORING_UNREGISTER_IOWQ_AFF:
return false;
default:
return true;
@@ -10137,6 +10176,18 @@ static int __io_uring_register(struct io_ring_ctx *ctx, unsigned opcode,
ret = io_register_rsrc_update(ctx, arg, nr_args,
IORING_RSRC_BUFFER);
break;
+ case IORING_REGISTER_IOWQ_AFF:
+ ret = -EINVAL;
+ if (!arg || !nr_args)
+ break;
+ ret = io_register_iowq_aff(ctx, arg, nr_args);
+ break;
+ case IORING_UNREGISTER_IOWQ_AFF:
+ ret = -EINVAL;
+ if (arg || nr_args)
+ break;
+ ret = io_unregister_iowq_aff(ctx);
+ break;
default:
ret = -EINVAL;
break;
