Re: [RFC PATCH 4/4] vhost: Add cgroup-aware creation of worker threads
From: "Michael S. Tsirkin" <mst@redhat.com>
Date: 2015-07-27 21:12:22
Also in:
cgroups, kvm, lkml
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 <redacted>
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.
quoted hunk ↗ jump to hunk
--- 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