On 2017年10月17日 15:54, Michal Hocko wrote:
> 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
>
OK, thanks.
>> +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?
>
I meant to make it more general other than ENABLE_NUMA_STAT(non 0 is enough),
but it will make it hard to scale, as you said.
So, it would be like this:
0 -- disable
1 -- enable
other value is invalid.
May add option 2 later for auto if necessary:)
>> + 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
>>
>
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