Re: [PATCH v4 3/6] mm: shmem: add multi-size THP sysfs interface for anonymous shmem

[Baolin Wang <baolin.wang@linux.alibaba.com>]

On 2024/6/10 20:23, Daniel Gomez wrote:
> Hi Baolin,
> On Tue, Jun 04, 2024 at 06:17:47PM +0800, Baolin Wang wrote:
>> To support the use of mTHP with anonymous shmem, add a new sysfs interface
>> 'shmem_enabled' in the '/sys/kernel/mm/transparent_hugepage/hugepages-kB/'
>> directory for each mTHP to control whether shmem is enabled for that mTHP,
>> with a value similar to the top level 'shmem_enabled', which can be set to:
>> "always", "inherit (to inherit the top level setting)", "within_size", "advise",
>> "never". An 'inherit' option is added to ensure compatibility with these
>> global settings, and the options 'force' and 'deny' are dropped, which are
>> rather testing artifacts from the old ages.
>>
>> By default, PMD-sized hugepages have enabled="inherit" and all other hugepage
>> sizes have enabled="never" for '/sys/kernel/mm/transparent_hugepage/hugepages-xxkB/shmem_enabled'.
>>
>> In addition, if top level value is 'force', then only PMD-sized hugepages
>> have enabled="inherit", otherwise configuration will be failed and vice versa.
>> That means now we will avoid using non-PMD sized THP to override the global
>> huge allocation.
>>
>> Signed-off-by: Baolin Wang <baolin.wang@linux.alibaba.com>
>> ---
>>   Documentation/admin-guide/mm/transhuge.rst | 23 ++++++
>>   include/linux/huge_mm.h                    | 10 +++
>>   mm/huge_memory.c                           | 11 +--
>>   mm/shmem.c                                 | 96 ++++++++++++++++++++++
>>   4 files changed, 132 insertions(+), 8 deletions(-)
>>
>> diff --git a/Documentation/admin-guide/mm/transhuge.rst b/Documentation/admin-guide/mm/transhuge.rst
>> index d414d3f5592a..b76d15e408b3 100644
>> --- a/Documentation/admin-guide/mm/transhuge.rst
>> +++ b/Documentation/admin-guide/mm/transhuge.rst
>> @@ -332,6 +332,29 @@ deny
>>   force
>>       Force the huge option on for all - very useful for testing;
>>   
>> +Shmem can also use "multi-size THP" (mTHP) by adding a new sysfs knob to control
>> +mTHP allocation: '/sys/kernel/mm/transparent_hugepage/hugepages-<size>kB/shmem_enabled',
>> +and its value for each mTHP is essentially consistent with the global setting.
>> +An 'inherit' option is added to ensure compatibility with these global settings.
>> +Conversely, the options 'force' and 'deny' are dropped, which are rather testing
>> +artifacts from the old ages.
>> +always
>> +    Attempt to allocate <size> huge pages every time we need a new page;
>> +
>> +inherit
>> +    Inherit the top-level "shmem_enabled" value. By default, PMD-sized hugepages
>> +    have enabled="inherit" and all other hugepage sizes have enabled="never";
>> +
>> +never
>> +    Do not allocate <size> huge pages;
>> +
>> +within_size
>> +    Only allocate <size> huge page if it will be fully within i_size.
>> +    Also respect fadvise()/madvise() hints;
>> +
>> +advise
>> +    Only allocate <size> huge pages if requested with fadvise()/madvise();
>> +
>>   Need of application restart
>>   ===========================
>>   
>> diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
>> index 020e2344eb86..fac21548c5de 100644
>> --- a/include/linux/huge_mm.h
>> +++ b/include/linux/huge_mm.h
>> @@ -6,6 +6,7 @@
>>   #include <linux/mm_types.h>
>>   
>>   #include <linux/fs.h> /* only for vma_is_dax() */
>> +#include <linux/kobject.h>
>>   
>>   vm_fault_t do_huge_pmd_anonymous_page(struct vm_fault *vmf);
>>   int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm,
>> @@ -63,6 +64,7 @@ ssize_t single_hugepage_flag_show(struct kobject *kobj,
>>   				  struct kobj_attribute *attr, char *buf,
>>   				  enum transparent_hugepage_flag flag);
>>   extern struct kobj_attribute shmem_enabled_attr;
>> +extern struct kobj_attribute thpsize_shmem_enabled_attr;
>>   
>>   /*
>>    * Mask of all large folio orders supported for anonymous THP; all orders up to
>> @@ -265,6 +267,14 @@ unsigned long thp_vma_allowable_orders(struct vm_area_struct *vma,
>>   	return __thp_vma_allowable_orders(vma, vm_flags, tva_flags, orders);
>>   }
>>   
>> +struct thpsize {
>> +	struct kobject kobj;
>> +	struct list_head node;
>> +	int order;
>> +};
>> +
>> +#define to_thpsize(kobj) container_of(kobj, struct thpsize, kobj)
>> +
>>   enum mthp_stat_item {
>>   	MTHP_STAT_ANON_FAULT_ALLOC,
>>   	MTHP_STAT_ANON_FAULT_FALLBACK,
>> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
>> index 8e49f402d7c7..1360a1903b66 100644
>> --- a/mm/huge_memory.c
>> +++ b/mm/huge_memory.c
>> @@ -449,14 +449,6 @@ static void thpsize_release(struct kobject *kobj);
>>   static DEFINE_SPINLOCK(huge_anon_orders_lock);
>>   static LIST_HEAD(thpsize_list);
>>   
>> -struct thpsize {
>> -	struct kobject kobj;
>> -	struct list_head node;
>> -	int order;
>> -};
>> -
>> -#define to_thpsize(kobj) container_of(kobj, struct thpsize, kobj)
>> -
>>   static ssize_t thpsize_enabled_show(struct kobject *kobj,
>>   				    struct kobj_attribute *attr, char *buf)
>>   {
>> @@ -517,6 +509,9 @@ static struct kobj_attribute thpsize_enabled_attr =
>>   
>>   static struct attribute *thpsize_attrs[] = {
>>   	&thpsize_enabled_attr.attr,
>> +#ifdef CONFIG_SHMEM
>> +	&thpsize_shmem_enabled_attr.attr,
>> +#endif
>>   	NULL,
>>   };
>>   
>> diff --git a/mm/shmem.c b/mm/shmem.c
>> index ae358efc397a..643ff7516b4d 100644
>> --- a/mm/shmem.c
>> +++ b/mm/shmem.c
>> @@ -131,6 +131,14 @@ struct shmem_options {
>>   #define SHMEM_SEEN_QUOTA 32
>>   };
>>   
>> +#ifdef CONFIG_TRANSPARENT_HUGEPAGE
>> +static unsigned long huge_anon_shmem_orders_always __read_mostly;
>> +static unsigned long huge_anon_shmem_orders_madvise __read_mostly;
>> +static unsigned long huge_anon_shmem_orders_inherit __read_mostly;
>> +static unsigned long huge_anon_shmem_orders_within_size __read_mostly;
>> +static DEFINE_SPINLOCK(huge_anon_shmem_orders_lock);
>> +#endif
> 
> Since we are also applying the new sysfs knob controls to tmpfs and anon mm,
> should we rename this to get rid of the anon prefix?

Sure. I want to do this in the patch set of mTHP support tmpfs 
originally, but yes, I can just drop the 'anon' prefix as a preparation.