On Mon, Jul 13, 2015 at 12:07:35AM -0400, Bandan Das wrote:
> With the help of the cgroup function to compare groups introduced
> in the previous patch, this changes worker creation policy.
> If the new device belongs to different cgroups than any of the
> devices we are currently serving, we end up creating a new worker
> thread even if we haven't reached the devs_per_worker threshold
>
> Signed-off-by: Bandan Das <bsd@xxxxxxxxxx>
Would it make sense to integrate this in the work-queue mechanism somehow?
Just a thought - correctly accounting kernel's work
on behalf of specific userspace groups might have value generally.
Or is the usecase too special?
Cc Tejun for comments.
> ---
> drivers/vhost/vhost.c | 47 +++++++++++++++++++++++++++++++++++++++--------
> 1 file changed, 39 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
> index 6a5d4c0..dc0fa37 100644
> --- a/drivers/vhost/vhost.c
> +++ b/drivers/vhost/vhost.c
> @@ -261,12 +261,6 @@ static int vhost_worker(void *data)
> use_mm(dev->mm);
> }
>
> - /* TODO: Consider a more elegant solution */
> - if (worker->owner != dev->owner) {
> - /* Should check for return value */
> - cgroup_attach_task_all(dev->owner, current);
> - worker->owner = dev->owner;
> - }
> work->fn(work);
> if (need_resched())
> schedule();
> @@ -278,6 +272,36 @@ static int vhost_worker(void *data)
> return 0;
> }
>
> +struct vhost_attach_cgroups_struct {
> + struct vhost_work work;
> + struct task_struct *owner;
> + int ret;
> +};
> +
> +static void vhost_attach_cgroups_work(struct vhost_work *work)
> +{
> + struct vhost_attach_cgroups_struct *s;
> +
> + s = container_of(work, struct vhost_attach_cgroups_struct, work);
> + s->ret = cgroup_attach_task_all(s->owner, current);
> +}
> +
> +static void vhost_attach_cgroups(struct vhost_dev *dev,
> + struct vhost_worker *worker)
> +{
> + struct vhost_attach_cgroups_struct attach;
> +
> + attach.owner = dev->owner;
> + vhost_work_init(dev, &attach.work, vhost_attach_cgroups_work);
> + vhost_work_queue(worker, &attach.work);
> + vhost_work_flush(worker, &attach.work);
> +
> + if (!attach.ret)
> + worker->owner = dev->owner;
> +
> + dev->err = attach.ret;
> +}
> +
> static void vhost_create_worker(struct vhost_dev *dev)
> {
> struct vhost_worker *worker;
> @@ -300,8 +324,14 @@ static void vhost_create_worker(struct vhost_dev *dev)
>
> spin_lock_init(&worker->work_lock);
> INIT_LIST_HEAD(&worker->work_list);
> +
> + /* attach to the cgroups of the process that created us */
> + vhost_attach_cgroups(dev, worker);
> + if (dev->err)
> + goto therror;
> + worker->owner = dev->owner;
> +
> list_add(&worker->node, &pool->workers);
> - worker->owner = NULL;
> worker->num_devices++;
> total_vhost_workers++;
> dev->worker = worker;
> @@ -320,7 +350,8 @@ static int vhost_dev_assign_worker(struct vhost_dev *dev)
>
> mutex_lock(&vhost_pool->pool_lock);
> list_for_each_entry(worker, &vhost_pool->workers, node) {
> - if (worker->num_devices < devs_per_worker) {
> + if (worker->num_devices < devs_per_worker &&
> + (!cgroup_match_groups(dev->owner, worker->owner))) {
> dev->worker = worker;
> dev->worker_assigned = true;
> worker->num_devices++;
> --
> 2.4.3
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