Messages in this thread | | | From | Jason Wang <> | Date | Thu, 24 Mar 2022 10:34:09 +0800 | Subject | Re: [PATCH 1/2] vdpa: mlx5: prevent cvq work from hogging CPU |
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On Thu, Mar 24, 2022 at 8:54 AM Hillf Danton <hdanton@sina.com> wrote: > > On Tue, 22 Mar 2022 09:59:14 +0800 Jason Wang wrote: > > > > Yes, there will be no "infinite" loop, but since the loop is triggered > > by userspace. It looks to me it will delay the flush/drain of the > > workqueue forever which is still suboptimal. > > Usually it is barely possible to shoot two birds using a stone. > > Given the "forever", I am inclined to not running faster, hehe, though > another cobble is to add another line in the loop checking if mvdev is > unregistered, and for example make mvdev->cvq unready before destroying > workqueue. > > static void mlx5_vdpa_dev_del(struct vdpa_mgmt_dev *v_mdev, struct vdpa_device *dev) > { > struct mlx5_vdpa_mgmtdev *mgtdev = container_of(v_mdev, struct mlx5_vdpa_mgmtdev, mgtdev); > struct mlx5_vdpa_dev *mvdev = to_mvdev(dev); > struct mlx5_vdpa_net *ndev = to_mlx5_vdpa_ndev(mvdev); > > mlx5_notifier_unregister(mvdev->mdev, &ndev->nb); > destroy_workqueue(mvdev->wq); > _vdpa_unregister_device(dev); > mgtdev->ndev = NULL; > } >
Yes, so we had
1) using a quota for re-requeue 2) using something like
while (READ_ONCE(cvq->ready)) { ... cond_resched(); }
There should not be too much difference except we need to use cancel_work_sync() instead of flush_work for 1).
I would keep the code as is but if you stick I can change.
Thanks
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