Re: [PATCH v2 2/3] mm: Tidy up shmem mTHP controls and stats

[Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx>]

On 2024/7/22 15:33, Ryan Roberts wrote:
> On 22/07/2024 07:14, Baolin Wang wrote:
> > On 2024/7/16 21:59, 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.
> >
> > Make sense.
> >
> > > 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.
> >
> > OK.
> >
> > > Signed-off-by: Ryan Roberts <ryan.roberts@xxxxxxx>
> > > ---
> > >    mm/huge_memory.c | 110 ++++++++++++++++++++++++++++++++++-------------
> > >    1 file changed, 80 insertions(+), 30 deletions(-)
> > >
> > > diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> > > index f4be468e06a4..578ac212c172 100644
> > > --- a/mm/huge_memory.c
> > > +++ b/mm/huge_memory.c
> > > @@ -463,8 +463,8 @@ 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;
> > > @@ -481,9 +481,9 @@ 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;
> > > @@ -525,19 +525,27 @@ 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 const struct kobj_type thpsize_ktype = {
> > > @@ -583,57 +591,99 @@ 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,
> > >        &swpout_attr.attr,
> > >        &swpout_fallback_attr.attr,
> > > -    &shmem_alloc_attr.attr,
> > > -    &shmem_fallback_attr.attr,
> > > -    &shmem_fallback_charge_attr.attr,
> > >        &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,
> >
> > Shmem should also support swpout_* counters.
>
> OK, so to put it another way, swpout_* stats are required all orders in
> (THP_ORDERS_ALL_ANON | THP_ORDERS_ALL_FILE_DEFAULT) if CONFIG_SHMEM is defined,
> else all orders in THP_ORDERS_ALL_ANON. Have I understood correctly?
>
> If so, I'll fix that in the next version.

Yes, I think so.