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Message-ID: <55EE9AE0.5030508@mellanox.com>
Date: Tue, 8 Sep 2015 11:22:56 +0300
From: Haggai Eran <haggaie@...lanox.com>
To: Parav Pandit <pandit.parav@...il.com>, <cgroups@...r.kernel.org>,
<linux-doc@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
<linux-rdma@...r.kernel.org>, <tj@...nel.org>,
<lizefan@...wei.com>, <hannes@...xchg.org>, <dledford@...hat.com>
CC: <corbet@....net>, <james.l.morris@...cle.com>, <serge@...lyn.com>,
<ogerlitz@...lanox.com>, <matanb@...lanox.com>,
<raindel@...lanox.com>, <akpm@...ux-foundation.org>,
<linux-security-module@...r.kernel.org>
Subject: Re: [PATCH 5/7] devcg: device cgroup's extension for RDMA resource.
On 07/09/2015 23:38, Parav Pandit wrote:
> +/* RDMA resources from device cgroup perspective */
> +enum devcgroup_rdma_rt {
> + DEVCG_RDMA_RES_TYPE_UCTX,
> + DEVCG_RDMA_RES_TYPE_CQ,
> + DEVCG_RDMA_RES_TYPE_PD,
> + DEVCG_RDMA_RES_TYPE_AH,
> + DEVCG_RDMA_RES_TYPE_MR,
> + DEVCG_RDMA_RES_TYPE_MW,
I didn't see memory windows in dev_cgroup_files in patch 3. Is it used?
> + DEVCG_RDMA_RES_TYPE_SRQ,
> + DEVCG_RDMA_RES_TYPE_QP,
> + DEVCG_RDMA_RES_TYPE_FLOW,
> + DEVCG_RDMA_RES_TYPE_MAX,
> +};
> +struct devcgroup_rdma_tracker {
> + int limit;
> + atomic_t usage;
> + int failcnt;
> +};
Have you considered using struct res_counter?
> + * RDMA resource limits are hierarchical, so the highest configured limit of
> + * the hierarchy is enforced. Allowing resource limit configuration to default
> + * cgroup allows fair share to kernel space ULPs as well.
In what way is the highest configured limit of the hierarchy enforced? I
would expect all the limits along the hierarchy to be enforced.
> +int devcgroup_rdma_get_max_resource(struct seq_file *sf, void *v)
> +{
> + struct dev_cgroup *dev_cg = css_to_devcgroup(seq_css(sf));
> + int type = seq_cft(sf)->private;
> + u32 usage;
> +
> + if (dev_cg->rdma.tracker[type].limit == DEVCG_RDMA_MAX_RESOURCES) {
> + seq_printf(sf, "%s\n", DEVCG_RDMA_MAX_RESOURCE_STR);
> + } else {
> + usage = dev_cg->rdma.tracker[type].limit;
If this is the resource limit, don't name it 'usage'.
> + seq_printf(sf, "%u\n", usage);
> + }
> + return 0;
> +}
> +int devcgroup_rdma_get_max_resource(struct seq_file *sf, void *v)
> +{
> + struct dev_cgroup *dev_cg = css_to_devcgroup(seq_css(sf));
> + int type = seq_cft(sf)->private;
> + u32 usage;
> +
> + if (dev_cg->rdma.tracker[type].limit == DEVCG_RDMA_MAX_RESOURCES) {
> + seq_printf(sf, "%s\n", DEVCG_RDMA_MAX_RESOURCE_STR);
I'm not sure hiding the actual number is good, especially in the
show_usage case.
> + } else {
> + usage = dev_cg->rdma.tracker[type].limit;
> + seq_printf(sf, "%u\n", usage);
> + }
> + return 0;
> +}
> +void devcgroup_rdma_uncharge_resource(struct ib_ucontext *ucontext,
> + enum devcgroup_rdma_rt type, int num)
> +{
> + struct dev_cgroup *dev_cg, *p;
> + struct task_struct *ctx_task;
> +
> + if (!num)
> + return;
> +
> + /* get cgroup of ib_ucontext it belong to, to uncharge
> + * so that when its called from any worker tasks or any
> + * other tasks to which this resource doesn't belong to,
> + * it can be uncharged correctly.
> + */
> + if (ucontext)
> + ctx_task = get_pid_task(ucontext->tgid, PIDTYPE_PID);
> + else
> + ctx_task = current;
> + dev_cg = task_devcgroup(ctx_task);
> +
> + spin_lock(&ctx_task->rdma_res_counter->lock);
Don't you need an rcu read lock and rcu_dereference to access
rdma_res_counter?
> + ctx_task->rdma_res_counter->usage[type] -= num;
> +
> + for (p = dev_cg; p; p = parent_devcgroup(p))
> + uncharge_resource(p, type, num);
> +
> + spin_unlock(&ctx_task->rdma_res_counter->lock);
> +
> + if (type == DEVCG_RDMA_RES_TYPE_UCTX)
> + rdma_free_res_counter(ctx_task);
> +}
> +EXPORT_SYMBOL(devcgroup_rdma_uncharge_resource);
> +int devcgroup_rdma_try_charge_resource(enum devcgroup_rdma_rt type, int num)
> +{
> + struct dev_cgroup *dev_cg = task_devcgroup(current);
> + struct task_rdma_res_counter *res_cnt = current->rdma_res_counter;
> + int status;
> +
> + if (!res_cnt) {
> + res_cnt = kzalloc(sizeof(*res_cnt), GFP_KERNEL);
> + if (!res_cnt)
> + return -ENOMEM;
> +
> + spin_lock_init(&res_cnt->lock);
> + rcu_assign_pointer(current->rdma_res_counter, res_cnt);
Don't you need the task lock to update rdma_res_counter here?
> + }
> +
> + /* synchronize with migration task by taking lock, to avoid
> + * race condition of performing cgroup resource migration
> + * in non atomic way with this task, which can leads to leaked
> + * resources in older cgroup.
> + */
> + spin_lock(&res_cnt->lock);
> + status = try_charge_resource(dev_cg, type, num);
> + if (status)
> + goto busy;
> +
> + /* single task updating its rdma resource usage, so atomic is
> + * not required.
> + */
> + current->rdma_res_counter->usage[type] += num;
> +
> +busy:
> + spin_unlock(&res_cnt->lock);
> + return status;
> +}
> +EXPORT_SYMBOL(devcgroup_rdma_try_charge_resource);
Regards,
Haggai
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