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    SubjectRe: [PATCH 07/18] io-controller: Export disk time used and nr sectors dipatched through cgroups
    Vivek Goyal wrote:
    ...
    >
    > +/*
    > + * traverse through all the io_groups associated with this cgroup and calculate
    > + * the aggr disk time received by all the groups on respective disks.
    > + */
    > +static u64 calculate_aggr_disk_time(struct io_cgroup *iocg)
    > +{
    > + struct io_group *iog;
    > + struct hlist_node *n;
    > + u64 disk_time = 0;
    > +
    > + rcu_read_lock();

    This function is in slow-path, so no need to call rcu_read_lock(), just need to ensure
    that the caller already holds the iocg->lock.

    > + hlist_for_each_entry_rcu(iog, n, &iocg->group_data, group_node) {
    > + /*
    > + * There might be groups which are not functional and
    > + * waiting to be reclaimed upon cgoup deletion.
    > + */
    > + if (rcu_dereference(iog->key))
    > + disk_time += iog->entity.total_service;
    > + }
    > + rcu_read_unlock();
    > +
    > + return disk_time;
    > +}
    > +

    --
    Regards
    Gui Jianfeng



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