On Tue 17-10-17 09:20:58, Kemi Wang wrote:
[...]
Other than two remarks below, it looks good to me and it also looks
simpler.
> diff --git a/mm/vmstat.c b/mm/vmstat.c
> index 4bb13e7..e746ed1 100644
> --- a/mm/vmstat.c
> +++ b/mm/vmstat.c
> @@ -32,6 +32,76 @@
>
> #define NUMA_STATS_THRESHOLD (U16_MAX - 2)
>
> +#ifdef CONFIG_NUMA
> +int sysctl_vm_numa_stat = ENABLE_NUMA_STAT;
> +static DEFINE_MUTEX(vm_numa_stat_lock);
You can scope this mutex to the sysctl handler function
> +int sysctl_vm_numa_stat_handler(struct ctl_table *table, int write,
> + void __user *buffer, size_t *length, loff_t *ppos)
> +{
> + int ret, oldval;
> +
> + mutex_lock(&vm_numa_stat_lock);
> + if (write)
> + oldval = sysctl_vm_numa_stat;
> + ret = proc_dointvec(table, write, buffer, length, ppos);
> + if (ret || !write)
> + goto out;
> +
> + if (oldval == sysctl_vm_numa_stat)
> + goto out;
> + else if (oldval == DISABLE_NUMA_STAT) {
So basically any value will enable numa stats. This means that we would
never be able to extend this interface to e.g. auto mode (say value 2).
I guess you meant to check sysctl_vm_numa_stat == ENABLE_NUMA_STAT?
> + static_branch_enable(&vm_numa_stat_key);
> + pr_info("enable numa statistics\n");
> + } else if (sysctl_vm_numa_stat == DISABLE_NUMA_STAT) {
> + static_branch_disable(&vm_numa_stat_key);
> + invalid_numa_statistics();
> + pr_info("disable numa statistics, and clear numa counters\n");
> + }
> +
> +out:
> + mutex_unlock(&vm_numa_stat_lock);
> + return ret;
> +}
> +#endif
> +
> #ifdef CONFIG_VM_EVENT_COUNTERS
> DEFINE_PER_CPU(struct vm_event_state, vm_event_states) = {{0}};
> EXPORT_PER_CPU_SYMBOL(vm_event_states);
> --
> 2.7.4
>
--
Michal Hocko
SUSE Labs
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