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

Daniel Gomez
2024-06-10T12:23:08Z

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?

> +
> #ifdef CONFIG_TMPFS
> static unsigned long shmem_default_max_blocks(void)
> {
> @@ -4672,6 +4680,12 @@ void __init shmem_init(void)
> SHMEM_SB(shm_mnt->mnt_sb)->huge = shmem_huge;
> else
> shmem_huge = SHMEM_HUGE_NEVER; /* just in case it was patched */
> +
> + /*
> + * Default to setting PMD-sized THP to inherit the global setting and
> + * disable all other multi-size THPs, when anonymous shmem uses mTHP.
> + */
> + huge_anon_shmem_orders_inherit = BIT(HPAGE_PMD_ORDER);
> #endif
> return;
>
> @@ -4731,6 +4745,11 @@ static ssize_t shmem_enabled_store(struct kobject *kobj,
> huge != SHMEM_HUGE_NEVER && huge != SHMEM_HUGE_DENY)
> return -EINVAL;
>
> + /* Do not override huge allocation policy with non-PMD sized mTHP */
> + if (huge == SHMEM_HUGE_FORCE &&
> + huge_anon_shmem_orders_inherit != BIT(HPAGE_PMD_ORDER))
> + return -EINVAL;
> +
> shmem_huge = huge;
> if (shmem_huge > SHMEM_HUGE_DENY)
> SHMEM_SB(shm_mnt->mnt_sb)->huge = shmem_huge;
> @@ -4738,6 +4757,83 @@ static ssize_t shmem_enabled_store(struct kobject *kobj,
> }
>
> struct kobj_attribute shmem_enabled_attr = __ATTR_RW(shmem_enabled);
> +
> +static ssize_t thpsize_shmem_enabled_show(struct kobject *kobj,
> + struct kobj_attribute *attr, char *buf)
> +{
> + int order = to_thpsize(kobj)->order;
> + const char *output;
> +
> + if (test_bit(order, &huge_anon_shmem_orders_always))
> + output = "[always] inherit within_size advise never";
> + else if (test_bit(order, &huge_anon_shmem_orders_inherit))
> + output = "always [inherit] within_size advise never";
> + else if (test_bit(order, &huge_anon_shmem_orders_within_size))
> + output = "always inherit [within_size] advise never";
> + else if (test_bit(order, &huge_anon_shmem_orders_madvise))
> + output = "always inherit within_size [advise] never";
> + else
> + output = "always inherit within_size advise [never]";
> +
> + return sysfs_emit(buf, "%s\n", output);
> +}
> +
> +static ssize_t thpsize_shmem_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;
> +
> + if (sysfs_streq(buf, "always")) {
> + spin_lock(&huge_anon_shmem_orders_lock);
> + clear_bit(order, &huge_anon_shmem_orders_inherit);
> + clear_bit(order, &huge_anon_shmem_orders_madvise);
> + clear_bit(order, &huge_anon_shmem_orders_within_size);
> + set_bit(order, &huge_anon_shmem_orders_always);
> + spin_unlock(&huge_anon_shmem_orders_lock);
> + } else if (sysfs_streq(buf, "inherit")) {
> + /* Do not override huge allocation policy with non-PMD sized mTHP */
> + if (shmem_huge == SHMEM_HUGE_FORCE &&
> + order != HPAGE_PMD_ORDER)
> + return -EINVAL;
> +
> + spin_lock(&huge_anon_shmem_orders_lock);
> + clear_bit(order, &huge_anon_shmem_orders_always);
> + clear_bit(order, &huge_anon_shmem_orders_madvise);
> + clear_bit(order, &huge_anon_shmem_orders_within_size);
> + set_bit(order, &huge_anon_shmem_orders_inherit);
> + spin_unlock(&huge_anon_shmem_orders_lock);
> + } else if (sysfs_streq(buf, "within_size")) {
> + spin_lock(&huge_anon_shmem_orders_lock);
> + clear_bit(order, &huge_anon_shmem_orders_always);
> + clear_bit(order, &huge_anon_shmem_orders_inherit);
> + clear_bit(order, &huge_anon_shmem_orders_madvise);
> + set_bit(order, &huge_anon_shmem_orders_within_size);
> + spin_unlock(&huge_anon_shmem_orders_lock);
> + } else if (sysfs_streq(buf, "madvise")) {
> + spin_lock(&huge_anon_shmem_orders_lock);
> + clear_bit(order, &huge_anon_shmem_orders_always);
> + clear_bit(order, &huge_anon_shmem_orders_inherit);
> + clear_bit(order, &huge_anon_shmem_orders_within_size);
> + set_bit(order, &huge_anon_shmem_orders_madvise);
> + spin_unlock(&huge_anon_shmem_orders_lock);
> + } else if (sysfs_streq(buf, "never")) {
> + spin_lock(&huge_anon_shmem_orders_lock);
> + clear_bit(order, &huge_anon_shmem_orders_always);
> + clear_bit(order, &huge_anon_shmem_orders_inherit);
> + clear_bit(order, &huge_anon_shmem_orders_within_size);
> + clear_bit(order, &huge_anon_shmem_orders_madvise);
> + spin_unlock(&huge_anon_shmem_orders_lock);
> + } else {
> + ret = -EINVAL;
> + }
> +
> + return ret;
> +}
> +
> +struct kobj_attribute thpsize_shmem_enabled_attr =
> + __ATTR(shmem_enabled, 0644, thpsize_shmem_enabled_show, thpsize_shmem_enabled_store);
> #endif /* CONFIG_TRANSPARENT_HUGEPAGE && CONFIG_SYSFS */
>
> #else /* !CONFIG_SHMEM */
> --
> 2.39.3
>