Re: [PATCH v3 2/2] mm: Tidy up shmem mTHP controls and stats

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Hi Andrew,


On 09/08/2024 09:31, Baolin Wang wrote:
> 
> 
> On 2024/8/8 19:18, Ryan Roberts wrote:
>> Previously we had a situation where shmem mTHP controls and stats were
>> not exposed for some supported sizes and were exposed for some
>> unsupported sizes. So let's clean that up.
>>
>> Anon mTHP can support all large orders [2, PMD_ORDER]. But shmem can
>> support all large orders [1, MAX_PAGECACHE_ORDER]. However, per-size
>> shmem controls and stats were previously being exposed for all the anon
>> mTHP orders, meaning order-1 was not present, and for arm64 64K base
>> pages, orders 12 and 13 were exposed but were not supported internally.
>>
>> Tidy this all up by defining ctrl and stats attribute groups for anon
>> and file separately. Anon ctrl and stats groups are populated for all
>> orders in THP_ORDERS_ALL_ANON and file ctrl and stats groups are
>> populated for all orders in THP_ORDERS_ALL_FILE_DEFAULT.
>>
>> Additionally, create "any" ctrl and stats attribute groups which are
>> populated for all orders in (THP_ORDERS_ALL_ANON |
>> THP_ORDERS_ALL_FILE_DEFAULT). swpout stats use this since they apply to
>> anon and shmem.
>>
>> The side-effect of all this is that different hugepage-*kB directories
>> contain different sets of controls and stats, depending on which memory
>> types support that size. This approach is preferred over the
>> alternative, which is to populate dummy controls and stats for memory
>> types that do not support a given size.
>>
>> Signed-off-by: Ryan Roberts <ryan.roberts@xxxxxxx>
>> ---
>>   mm/huge_memory.c | 144 +++++++++++++++++++++++++++++++++++++----------
>>   1 file changed, 114 insertions(+), 30 deletions(-)
>>
>> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
>> index 0c3075ee00012..082d86b7c6c2f 100644
>> --- a/mm/huge_memory.c
>> +++ b/mm/huge_memory.c
>> @@ -482,8 +482,8 @@ static void thpsize_release(struct kobject *kobj);
>>   static DEFINE_SPINLOCK(huge_anon_orders_lock);
>>   static LIST_HEAD(thpsize_list);
>>   -static ssize_t thpsize_enabled_show(struct kobject *kobj,
>> -                    struct kobj_attribute *attr, char *buf)
>> +static ssize_t anon_enabled_show(struct kobject *kobj,
>> +                 struct kobj_attribute *attr, char *buf)
>>   {
>>       int order = to_thpsize(kobj)->order;
>>       const char *output;
>> @@ -500,9 +500,9 @@ static ssize_t thpsize_enabled_show(struct kobject *kobj,
>>       return sysfs_emit(buf, "%s\n", output);
>>   }
>>   -static ssize_t thpsize_enabled_store(struct kobject *kobj,
>> -                     struct kobj_attribute *attr,
>> -                     const char *buf, size_t count)
>> +static ssize_t anon_enabled_store(struct kobject *kobj,
>> +                  struct kobj_attribute *attr,
>> +                  const char *buf, size_t count)
>>   {
>>       int order = to_thpsize(kobj)->order;
>>       ssize_t ret = count;
>> @@ -544,19 +544,35 @@ static ssize_t thpsize_enabled_store(struct kobject *kobj,
>>       return ret;
>>   }
>>   -static struct kobj_attribute thpsize_enabled_attr =
>> -    __ATTR(enabled, 0644, thpsize_enabled_show, thpsize_enabled_store);
>> +static struct kobj_attribute anon_enabled_attr =
>> +    __ATTR(enabled, 0644, anon_enabled_show, anon_enabled_store);
>>   -static struct attribute *thpsize_attrs[] = {
>> -    &thpsize_enabled_attr.attr,
>> +static struct attribute *anon_ctrl_attrs[] = {
>> +    &anon_enabled_attr.attr,
>> +    NULL,
>> +};
>> +
>> +static const struct attribute_group anon_ctrl_attr_grp = {
>> +    .attrs = anon_ctrl_attrs,
>> +};
>> +
>> +static struct attribute *file_ctrl_attrs[] = {
>>   #ifdef CONFIG_SHMEM
>>       &thpsize_shmem_enabled_attr.attr,
>>   #endif
>>       NULL,
>>   };
>>   -static const struct attribute_group thpsize_attr_group = {
>> -    .attrs = thpsize_attrs,
>> +static const struct attribute_group file_ctrl_attr_grp = {
>> +    .attrs = file_ctrl_attrs,
>> +};
>> +
>> +static struct attribute *any_ctrl_attrs[] = {
>> +    NULL,
>> +};
>> +
>> +static const struct attribute_group any_ctrl_attr_grp = {
>> +    .attrs = any_ctrl_attrs,
>>   };
> 
> I wonder why adding a NULL group?
> 
>>     static const struct kobj_type thpsize_ktype = {
>> @@ -595,64 +611,132 @@ DEFINE_MTHP_STAT_ATTR(anon_fault_fallback,
>> MTHP_STAT_ANON_FAULT_FALLBACK);
>>   DEFINE_MTHP_STAT_ATTR(anon_fault_fallback_charge,
>> MTHP_STAT_ANON_FAULT_FALLBACK_CHARGE);
>>   DEFINE_MTHP_STAT_ATTR(swpout, MTHP_STAT_SWPOUT);
>>   DEFINE_MTHP_STAT_ATTR(swpout_fallback, MTHP_STAT_SWPOUT_FALLBACK);
>> +#ifdef CONFIG_SHMEM
>>   DEFINE_MTHP_STAT_ATTR(shmem_alloc, MTHP_STAT_SHMEM_ALLOC);
>>   DEFINE_MTHP_STAT_ATTR(shmem_fallback, MTHP_STAT_SHMEM_FALLBACK);
>>   DEFINE_MTHP_STAT_ATTR(shmem_fallback_charge, MTHP_STAT_SHMEM_FALLBACK_CHARGE);
>> +#endif
>>   DEFINE_MTHP_STAT_ATTR(split, MTHP_STAT_SPLIT);
>>   DEFINE_MTHP_STAT_ATTR(split_failed, MTHP_STAT_SPLIT_FAILED);
>>   DEFINE_MTHP_STAT_ATTR(split_deferred, MTHP_STAT_SPLIT_DEFERRED);
>>   -static struct attribute *stats_attrs[] = {
>> +static struct attribute *anon_stats_attrs[] = {
>>       &anon_fault_alloc_attr.attr,
>>       &anon_fault_fallback_attr.attr,
>>       &anon_fault_fallback_charge_attr.attr,
>> +#ifndef CONFIG_SHMEM
>>       &swpout_attr.attr,
>>       &swpout_fallback_attr.attr,
>> -    &shmem_alloc_attr.attr,
>> -    &shmem_fallback_attr.attr,
>> -    &shmem_fallback_charge_attr.attr,
>> +#endif
>>       &split_attr.attr,
>>       &split_failed_attr.attr,
>>       &split_deferred_attr.attr,
>>       NULL,
>>   };
>>   -static struct attribute_group stats_attr_group = {
>> +static struct attribute_group anon_stats_attr_grp = {
>> +    .name = "stats",
>> +    .attrs = anon_stats_attrs,
>> +};
>> +
>> +static struct attribute *file_stats_attrs[] = {
>> +#ifdef CONFIG_SHMEM
>> +    &shmem_alloc_attr.attr,
>> +    &shmem_fallback_attr.attr,
>> +    &shmem_fallback_charge_attr.attr,
>> +#endif
>> +    NULL,
>> +};
>> +
>> +static struct attribute_group file_stats_attr_grp = {
>> +    .name = "stats",
>> +    .attrs = file_stats_attrs,
>> +};
>> +
>> +static struct attribute *any_stats_attrs[] = {
>> +#ifdef CONFIG_SHMEM
>> +    &swpout_attr.attr,
>> +    &swpout_fallback_attr.attr,
>> +#endif
> 
> Sorry I did not point it out in early version. I think file pages and shmem can
> also be split, while 'split_deferred' is only for anonymous page. So I think the
> any_stats_attrs should be:
> static struct attribute *any_stats_attrs[] = {
> #ifdef CONFIG_SHMEM
>     &swpout_attr.attr,
>     &swpout_fallback_attr.attr,
> #endif
>     &split_attr.attr,
>     &split_failed_attr.attr,
>     NULL,
> };

Could you please squash the following into this patch, which is already in
mm-unstable? I'm hoping this sufficient and I don't need to send a whole new
revision since there are changes on top of this in mm-unstable, which makes
things tricky.

----8<-----

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 382938e46f96f..5905957b1f70d 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -631,8 +631,6 @@ static struct attribute *anon_stats_attrs[] = {
        &swpout_attr.attr,
        &swpout_fallback_attr.attr,
 #endif
-       &split_attr.attr,
-       &split_failed_attr.attr,
        &split_deferred_attr.attr,
        &nr_anon_attr.attr,
        &nr_anon_partially_mapped_attr.attr,
@@ -663,6 +661,8 @@ static struct attribute *any_stats_attrs[] = {
        &swpout_attr.attr,
        &swpout_fallback_attr.attr,
 #endif
+       &split_attr.attr,
+       &split_failed_attr.attr,
        NULL,
 };

----8<-----

Thanks,
Ryan





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