[PATCH v5 0/5] mm: add more kernel parameters to control mTHP

[PATCH v5 0/5] mm: add more kernel parameters to control mTHP

[Maíra Canal]

This series introduces four patches related to the kernel parameters
controlling mTHP and a fifth patch replacing `strcpy()` for `strscpy()`
in the file `mm/huge_memory.c`.

The first patch is a straightforward documentation update, correcting
the format of the kernel parameter ``thp_anon=``.

The second, third, and fourth patches focus on controlling THP support for
shmem via the kernel command line. The second patch introduces a parameter to
control the global default huge page allocation policy for the internal
shmem mount. The third patch moves a piece of code to a shared header to ease
the implementation of the fourth patch. Finally, the fourth patch implements
a parameter similar to ``thp_anon=``, but for shmem.

The goal of these changes is to simplify the configuration of systems that
rely on mTHP support for shmem. For instance, a platform with a GPU that
benefits from huge pages may want to enable huge pages for shmem. Having
these kernel parameters streamlines the configuration process and ensures
consistency across setups.

Let me know your thoughts.

v1 -> v2: https://lore.kernel.org/linux-mm/20241027175743.1056710-1-mcanal@igalia.com/T/

* [1/3] s/fix the format/fix the doc in the commit's subject (Barry Song & David Hildenbrand)
* [1/3] Add Barry's A-b to PATCH 1/3 (Barry Song)
* [1/3] s/64KB/64K (David Hildenbrand)
* [1/3] Add David's A-b to PATCH 1/3 (David Hildenbrand)
* [2/3] Create the function `shmem_valid_huge()` to reduce code-duplication (Baolin Wang)
* [3/4] New PATCH: generalize the function `setup_thp_anon()` and add it to common file
* [4/4] Fix typo in the documentation: s/shmem_anon/thp_shmem (Barry Song)
* [4/4] Reduce code-duplication (Barry Song)

v2 -> v3: https://lore.kernel.org/linux-mm/20241029002324.1062723-1-mcanal@igalia.com/T/

* [2/4] Apply Wang's suggestion (Baolin Wang)
* [3/4] Delete PATCH 3/4 from v2 and implement ``thp_shmem=`` just like in v1 (Barry Song)
* [4/4] New PATCH: "mm: huge_memory: Use strscpy() instead of strcpy()"

v3 -> v4: https://lore.kernel.org/linux-mm/20241030130308.1066299-1-mcanal@igalia.com/T/

* [2/5] Improve commit message by including details about the use of the kernel parameter (Andrew Morton)
* [2/5] Add Baolin's R-b to PATCH 2/5 (Baolin Wang)
* [2/5] Add David's R-b to PATCH 2/5 (David Hildenbrand)
* [3/5] New PATCH: "mm: move ``get_order_from_str()`` to internal.h" (Barry Song & David Hildenbrand)
* [4/5] Improve commit message by including details about the use of the kernel parameter (Andrew Morton)
* [5/5] Add Lance's R-b to PATCH 5/5 (Lance Yang)

v4 -> v5: https://lore.kernel.org/linux-mm/20241101164313.1073238-2-mcanal@igalia.com/T/

* [3/5] Don't use personal e-mail address (Maíra Canal)

Best Regards,
- Maíra

Maíra Canal (5):
  mm: fix docs for the kernel parameter ``thp_anon=``
  mm: shmem: control THP support through the kernel command line
  mm: move ``get_order_from_str()`` to internal.h
  mm: shmem: override mTHP shmem default with a kernel parameter
  mm: huge_memory: Use strscpy() instead of strcpy()

 .../admin-guide/kernel-parameters.txt         |  19 +-
 Documentation/admin-guide/mm/transhuge.rst    |  25 ++-
 mm/huge_memory.c                              |  42 ++---
 mm/internal.h                                 |  22 +++
 mm/shmem.c                                    | 177 +++++++++++++++---
 5 files changed, 234 insertions(+), 51 deletions(-)

-- 
2.46.2

[PATCH v5 1/5] mm: fix docs for the kernel parameter ``thp_anon=``

[Maíra Canal]

If we add ``thp_anon=32,64K:always`` to the kernel command line, we
will see the following error:

[    0.000000] huge_memory: thp_anon=32,64K:always: error parsing string, ignoring setting

This happens because the correct format isn't ``thp_anon=<size>,<size>[KMG]:<state>```,
as [KMG] must follow each number to especify its unit. So, the correct
format is ``thp_anon=<size>[KMG],<size>[KMG]:<state>```.

Therefore, adjust the documentation to reflect the correct format of the
parameter ``thp_anon=``.

Fixes: dd4d30d1cdbe ("mm: override mTHP "enabled" defaults at kernel cmdline")
Signed-off-by: Maíra Canal <mcanal@igalia.com>
Acked-by: Barry Song <baohua@kernel.org>
Acked-by: David Hildenbrand <david@redhat.com>
---
 Documentation/admin-guide/kernel-parameters.txt | 2 +-
 Documentation/admin-guide/mm/transhuge.rst      | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 1518343bbe22..1666576acc0e 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -6688,7 +6688,7 @@
 			0: no polling (default)
 
 	thp_anon=	[KNL]
-			Format: <size>,<size>[KMG]:<state>;<size>-<size>[KMG]:<state>
+			Format: <size>[KMG],<size>[KMG]:<state>;<size>[KMG]-<size>[KMG]:<state>
 			state is one of "always", "madvise", "never" or "inherit".
 			Control the default behavior of the system with respect
 			to anonymous transparent hugepages.
diff --git a/Documentation/admin-guide/mm/transhuge.rst b/Documentation/admin-guide/mm/transhuge.rst
index 5caa3fb2feb1..abdf10a1c7db 100644
--- a/Documentation/admin-guide/mm/transhuge.rst
+++ b/Documentation/admin-guide/mm/transhuge.rst
@@ -303,7 +303,7 @@ control by passing the parameter ``transparent_hugepage=always`` or
 kernel command line.
 
 Alternatively, each supported anonymous THP size can be controlled by
-passing ``thp_anon=<size>,<size>[KMG]:<state>;<size>-<size>[KMG]:<state>``,
+passing ``thp_anon=<size>[KMG],<size>[KMG]:<state>;<size>[KMG]-<size>[KMG]:<state>``,
 where ``<size>`` is the THP size (must be a power of 2 of PAGE_SIZE and
 supported anonymous THP)  and ``<state>`` is one of ``always``, ``madvise``,
 ``never`` or ``inherit``.
-- 
2.46.2

[PATCH v5 2/5] mm: shmem: control THP support through the kernel command line

[Maíra Canal]

Add a new kernel command line to control the hugepage allocation policy
for the internal shmem mount, ``transparent_hugepage_shmem``. The
parameter is similar to ``transparent_hugepage`` and has the following
format:

transparent_hugepage_shmem=<policy>

where ``<policy>`` is one of the seven valid policies available for
shmem.

Configuring the default huge page allocation policy for the internal
shmem mount can be beneficial for DRM GPU drivers. Just as CPU
architectures, GPUs can also take advantage of huge pages, but this is
possible only if DRM GEM objects are backed by huge pages.

Since GEM uses shmem to allocate anonymous pageable memory, having control
over the default huge page allocation policy allows for the exploration of
huge pages use on GPUs that rely on GEM objects backed by shmem.

Signed-off-by: Maíra Canal <mcanal@igalia.com>
Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Acked-by: David Hildenbrand <david@redhat.com>
---
 .../admin-guide/kernel-parameters.txt         |  7 ++
 Documentation/admin-guide/mm/transhuge.rst    |  6 ++
 mm/shmem.c                                    | 72 +++++++++++++------
 3 files changed, 62 insertions(+), 23 deletions(-)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 1666576acc0e..acabb04d0dd4 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -6926,6 +6926,13 @@
 			See Documentation/admin-guide/mm/transhuge.rst
 			for more details.
 
+	transparent_hugepage_shmem= [KNL]
+			Format: [always|within_size|advise|never|deny|force]
+			Can be used to control the hugepage allocation policy for
+			the internal shmem mount.
+			See Documentation/admin-guide/mm/transhuge.rst
+			for more details.
+
 	trusted.source=	[KEYS]
 			Format: <string>
 			This parameter identifies the trust source as a backend
diff --git a/Documentation/admin-guide/mm/transhuge.rst b/Documentation/admin-guide/mm/transhuge.rst
index abdf10a1c7db..9c6f6da612c4 100644
--- a/Documentation/admin-guide/mm/transhuge.rst
+++ b/Documentation/admin-guide/mm/transhuge.rst
@@ -326,6 +326,12 @@ PMD_ORDER THP policy will be overridden. If the policy for PMD_ORDER
 is not defined within a valid ``thp_anon``, its policy will default to
 ``never``.
 
+Similarly to ``transparent_hugepage``, you can control the hugepage
+allocation policy for the internal shmem mount by using the kernel parameter
+``transparent_hugepage_shmem=<policy>``, where ``<policy>`` is one of the
+seven valid policies for shmem (``always``, ``within_size``, ``advise``,
+``never``, ``deny``, and ``force``).
+
 Hugepages in tmpfs/shmem
 ========================
 
diff --git a/mm/shmem.c b/mm/shmem.c
index 275251abd596..dfcc88ec6e34 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -582,24 +582,39 @@ static bool shmem_huge_global_enabled(struct inode *inode, pgoff_t index,
 	}
 }
 
-#if defined(CONFIG_SYSFS)
 static int shmem_parse_huge(const char *str)
 {
+	int huge;
+
+	if (!str)
+		return -EINVAL;
+
 	if (!strcmp(str, "never"))
-		return SHMEM_HUGE_NEVER;
-	if (!strcmp(str, "always"))
-		return SHMEM_HUGE_ALWAYS;
-	if (!strcmp(str, "within_size"))
-		return SHMEM_HUGE_WITHIN_SIZE;
-	if (!strcmp(str, "advise"))
-		return SHMEM_HUGE_ADVISE;
-	if (!strcmp(str, "deny"))
-		return SHMEM_HUGE_DENY;
-	if (!strcmp(str, "force"))
-		return SHMEM_HUGE_FORCE;
-	return -EINVAL;
+		huge = SHMEM_HUGE_NEVER;
+	else if (!strcmp(str, "always"))
+		huge = SHMEM_HUGE_ALWAYS;
+	else if (!strcmp(str, "within_size"))
+		huge = SHMEM_HUGE_WITHIN_SIZE;
+	else if (!strcmp(str, "advise"))
+		huge = SHMEM_HUGE_ADVISE;
+	else if (!strcmp(str, "deny"))
+		huge = SHMEM_HUGE_DENY;
+	else if (!strcmp(str, "force"))
+		huge = SHMEM_HUGE_FORCE;
+	else
+		return -EINVAL;
+
+	if (!has_transparent_hugepage() &&
+	    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_shmem_orders_inherit != BIT(HPAGE_PMD_ORDER))
+		return -EINVAL;
+
+	return huge;
 }
-#endif
 
 #if defined(CONFIG_SYSFS) || defined(CONFIG_TMPFS)
 static const char *shmem_format_huge(int huge)
@@ -5066,15 +5081,7 @@ static ssize_t shmem_enabled_store(struct kobject *kobj,
 
 	huge = shmem_parse_huge(tmp);
 	if (huge == -EINVAL)
-		return -EINVAL;
-	if (!has_transparent_hugepage() &&
-			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_shmem_orders_inherit != BIT(HPAGE_PMD_ORDER))
-		return -EINVAL;
+		return huge;
 
 	shmem_huge = huge;
 	if (shmem_huge > SHMEM_HUGE_DENY)
@@ -5171,6 +5178,25 @@ 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 */
 
+#if defined(CONFIG_TRANSPARENT_HUGEPAGE)
+
+static int __init setup_transparent_hugepage_shmem(char *str)
+{
+	int huge;
+
+	huge = shmem_parse_huge(str);
+	if (huge == -EINVAL) {
+		pr_warn("transparent_hugepage_shmem= cannot parse, ignored\n");
+		return huge;
+	}
+
+	shmem_huge = huge;
+	return 1;
+}
+__setup("transparent_hugepage_shmem=", setup_transparent_hugepage_shmem);
+
+#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
+
 #else /* !CONFIG_SHMEM */
 
 /*
-- 
2.46.2

[PATCH v5 3/5] mm: move ``get_order_from_str()`` to internal.h

[Maíra Canal]

In order to implement a kernel parameter similar to ``thp_anon=`` for
shmem, we'll need the function ``get_order_from_str()``.

Instead of duplicating the function, move the function to a shared
header, in which both mm/shmem.c and mm/huge_memory.c will be able to
use it.

Signed-off-by: Maíra Canal <mcanal@igalia.com>
---
 mm/huge_memory.c | 38 +++++++++++++++-----------------------
 mm/internal.h    | 22 ++++++++++++++++++++++
 2 files changed, 37 insertions(+), 23 deletions(-)

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index f92068864469..a6edbd8c4f49 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -958,26 +958,6 @@ static int __init setup_transparent_hugepage(char *str)
 }
 __setup("transparent_hugepage=", setup_transparent_hugepage);
 
-static inline int get_order_from_str(const char *size_str)
-{
-	unsigned long size;
-	char *endptr;
-	int order;
-
-	size = memparse(size_str, &endptr);
-
-	if (!is_power_of_2(size))
-		goto err;
-	order = get_order(size);
-	if (BIT(order) & ~THP_ORDERS_ALL_ANON)
-		goto err;
-
-	return order;
-err:
-	pr_err("invalid size %s in thp_anon boot parameter\n", size_str);
-	return -EINVAL;
-}
-
 static char str_dup[PAGE_SIZE] __initdata;
 static int __init setup_thp_anon(char *str)
 {
@@ -1007,10 +987,22 @@ static int __init setup_thp_anon(char *str)
 				start_size = strsep(&subtoken, "-");
 				end_size = subtoken;
 
-				start = get_order_from_str(start_size);
-				end = get_order_from_str(end_size);
+				start = get_order_from_str(start_size, THP_ORDERS_ALL_ANON);
+				end = get_order_from_str(end_size, THP_ORDERS_ALL_ANON);
 			} else {
-				start = end = get_order_from_str(subtoken);
+				start_size = end_size = subtoken;
+				start = end = get_order_from_str(subtoken,
+								 THP_ORDERS_ALL_ANON);
+			}
+
+			if (start == -EINVAL) {
+				pr_err("invalid size %s in thp_anon boot parameter\n", start_size);
+				goto err;
+			}
+
+			if (end == -EINVAL) {
+				pr_err("invalid size %s in thp_anon boot parameter\n", end_size);
+				goto err;
 			}
 
 			if (start < 0 || end < 0 || start > end)
diff --git a/mm/internal.h b/mm/internal.h
index d5b93c5b6364..5a7302baeed7 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -1291,6 +1291,28 @@ static inline bool alloc_zeroed(void)
 			&init_on_alloc);
 }
 
+/*
+ * Parses a string with mem suffixes into its order. Useful to parse kernel
+ * parameters.
+ */
+static inline int get_order_from_str(const char *size_str,
+				     unsigned long valid_orders)
+{
+	unsigned long size;
+	char *endptr;
+	int order;
+
+	size = memparse(size_str, &endptr);
+
+	if (!is_power_of_2(size))
+		return -EINVAL;
+	order = get_order(size);
+	if (BIT(order) & ~valid_orders)
+		return -EINVAL;
+
+	return order;
+}
+
 enum {
 	/* mark page accessed */
 	FOLL_TOUCH = 1 << 16,
-- 
2.46.2

Re: [PATCH v5 3/5] mm: move ``get_order_from_str()`` to internal.h

[Baolin Wang]

On 2024/11/2 00:54, Maíra Canal wrote:
> In order to implement a kernel parameter similar to ``thp_anon=`` for
> shmem, we'll need the function ``get_order_from_str()``.
> 
> Instead of duplicating the function, move the function to a shared
> header, in which both mm/shmem.c and mm/huge_memory.c will be able to
> use it.
> 
> Signed-off-by: Maíra Canal <mcanal@igalia.com>
> ---
>   mm/huge_memory.c | 38 +++++++++++++++-----------------------
>   mm/internal.h    | 22 ++++++++++++++++++++++
>   2 files changed, 37 insertions(+), 23 deletions(-)
> 
> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> index f92068864469..a6edbd8c4f49 100644
> --- a/mm/huge_memory.c
> +++ b/mm/huge_memory.c
> @@ -958,26 +958,6 @@ static int __init setup_transparent_hugepage(char *str)
>   }
>   __setup("transparent_hugepage=", setup_transparent_hugepage);
>   
> -static inline int get_order_from_str(const char *size_str)
> -{
> -	unsigned long size;
> -	char *endptr;
> -	int order;
> -
> -	size = memparse(size_str, &endptr);
> -
> -	if (!is_power_of_2(size))
> -		goto err;
> -	order = get_order(size);
> -	if (BIT(order) & ~THP_ORDERS_ALL_ANON)
> -		goto err;
> -
> -	return order;
> -err:
> -	pr_err("invalid size %s in thp_anon boot parameter\n", size_str);
> -	return -EINVAL;
> -}
> -
>   static char str_dup[PAGE_SIZE] __initdata;
>   static int __init setup_thp_anon(char *str)
>   {
> @@ -1007,10 +987,22 @@ static int __init setup_thp_anon(char *str)
>   				start_size = strsep(&subtoken, "-");
>   				end_size = subtoken;
>   
> -				start = get_order_from_str(start_size);
> -				end = get_order_from_str(end_size);
> +				start = get_order_from_str(start_size, THP_ORDERS_ALL_ANON);
> +				end = get_order_from_str(end_size, THP_ORDERS_ALL_ANON);
>   			} else {
> -				start = end = get_order_from_str(subtoken);
> +				start_size = end_size = subtoken;
> +				start = end = get_order_from_str(subtoken,
> +								 THP_ORDERS_ALL_ANON);
> +			}
> +
> +			if (start == -EINVAL) {
> +				pr_err("invalid size %s in thp_anon boot parameter\n", start_size);
> +				goto err;
> +			}
> +
> +			if (end == -EINVAL) {
> +				pr_err("invalid size %s in thp_anon boot parameter\n", end_size);
> +				goto err;
>   			}

There are already checks for ‘start’ and ‘end’ below, and will print 
error messages if error occurs. So I suspect whether these repeated 
checks and error infor are helpful.

Anyway, I don't have a strong preference.
Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>

Re: [PATCH v5 3/5] mm: move ``get_order_from_str()`` to internal.h

[Maíra Canal]

Hi Baolin,

On 03/11/24 23:25, Baolin Wang wrote:
> 
> 
> On 2024/11/2 00:54, Maíra Canal wrote:
>> In order to implement a kernel parameter similar to ``thp_anon=`` for
>> shmem, we'll need the function ``get_order_from_str()``.
>>
>> Instead of duplicating the function, move the function to a shared
>> header, in which both mm/shmem.c and mm/huge_memory.c will be able to
>> use it.
>>
>> Signed-off-by: Maíra Canal <mcanal@igalia.com>
>> ---
>>   mm/huge_memory.c | 38 +++++++++++++++-----------------------
>>   mm/internal.h    | 22 ++++++++++++++++++++++
>>   2 files changed, 37 insertions(+), 23 deletions(-)
>>
>> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
>> index f92068864469..a6edbd8c4f49 100644
>> --- a/mm/huge_memory.c
>> +++ b/mm/huge_memory.c
>> @@ -958,26 +958,6 @@ static int __init setup_transparent_hugepage(char 
>> *str)
>>   }
>>   __setup("transparent_hugepage=", setup_transparent_hugepage);
>> -static inline int get_order_from_str(const char *size_str)
>> -{
>> -    unsigned long size;
>> -    char *endptr;
>> -    int order;
>> -
>> -    size = memparse(size_str, &endptr);
>> -
>> -    if (!is_power_of_2(size))
>> -        goto err;
>> -    order = get_order(size);
>> -    if (BIT(order) & ~THP_ORDERS_ALL_ANON)
>> -        goto err;
>> -
>> -    return order;
>> -err:
>> -    pr_err("invalid size %s in thp_anon boot parameter\n", size_str);
>> -    return -EINVAL;
>> -}
>> -
>>   static char str_dup[PAGE_SIZE] __initdata;
>>   static int __init setup_thp_anon(char *str)
>>   {
>> @@ -1007,10 +987,22 @@ static int __init setup_thp_anon(char *str)
>>                   start_size = strsep(&subtoken, "-");
>>                   end_size = subtoken;
>> -                start = get_order_from_str(start_size);
>> -                end = get_order_from_str(end_size);
>> +                start = get_order_from_str(start_size, 
>> THP_ORDERS_ALL_ANON);
>> +                end = get_order_from_str(end_size, THP_ORDERS_ALL_ANON);
>>               } else {
>> -                start = end = get_order_from_str(subtoken);
>> +                start_size = end_size = subtoken;
>> +                start = end = get_order_from_str(subtoken,
>> +                                 THP_ORDERS_ALL_ANON);
>> +            }
>> +
>> +            if (start == -EINVAL) {
>> +                pr_err("invalid size %s in thp_anon boot 
>> parameter\n", start_size);
>> +                goto err;
>> +            }
>> +
>> +            if (end == -EINVAL) {
>> +                pr_err("invalid size %s in thp_anon boot 
>> parameter\n", end_size);
>> +                goto err;
>>               }
> 
> There are already checks for ‘start’ and ‘end’ below, and will print 
> error messages if error occurs. So I suspect whether these repeated 
> checks and error infor are helpful.

The idea is to explicitly show to the user which part of the kernel
parameter is broke. Instead of saying that something is broken, it is
going to return that, for example, "33K" is invalid.

Best Regards,
- Maíra

> 
> Anyway, I don't have a strong preference.
> Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>

[PATCH v5 4/5] mm: shmem: override mTHP shmem default with a kernel parameter

[Maíra Canal]

Add the ``thp_shmem=`` kernel command line to allow specifying the
default policy of each supported shmem hugepage size. The kernel parameter
accepts the following format:

thp_shmem=<size>[KMG],<size>[KMG]:<policy>;<size>[KMG]-<size>[KMG]:<policy>

For example,

thp_shmem=16K-64K:always;128K,512K:inherit;256K:advise;1M-2M:never;4M-8M:within_size

Some GPUs may benefit from using huge pages. Since DRM GEM uses shmem
to allocate anonymous pageable memory, it’s essential to control the huge
page allocation policy for the internal shmem mount. This control can be
achieved through the ``transparent_hugepage_shmem=`` parameter.

Beyond just setting the allocation policy, it’s crucial to have granular
control over the size of huge pages that can be allocated. The GPU may
support only specific huge page sizes, and allocating pages larger/smaller
than those sizes would be ineffective.

Signed-off-by: Maíra Canal <mcanal@igalia.com>
---
 .../admin-guide/kernel-parameters.txt         |  10 ++
 Documentation/admin-guide/mm/transhuge.rst    |  17 +++
 mm/shmem.c                                    | 105 +++++++++++++++++-
 3 files changed, 131 insertions(+), 1 deletion(-)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index acabb04d0dd4..b48d744d99b0 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -6700,6 +6700,16 @@
 			Force threading of all interrupt handlers except those
 			marked explicitly IRQF_NO_THREAD.
 
+	thp_shmem=	[KNL]
+			Format: <size>[KMG],<size>[KMG]:<policy>;<size>[KMG]-<size>[KMG]:<policy>
+			Control the default policy of each hugepage size for the
+			internal shmem mount. <policy> is one of policies available
+			for the shmem mount ("always", "inherit", "never", "within_size",
+			and "advise").
+			It can be used multiple times for multiple shmem THP sizes.
+			See Documentation/admin-guide/mm/transhuge.rst for more
+			details.
+
 	topology=	[S390,EARLY]
 			Format: {off | on}
 			Specify if the kernel should make use of the cpu
diff --git a/Documentation/admin-guide/mm/transhuge.rst b/Documentation/admin-guide/mm/transhuge.rst
index 9c6f6da612c4..5034915f4e8e 100644
--- a/Documentation/admin-guide/mm/transhuge.rst
+++ b/Documentation/admin-guide/mm/transhuge.rst
@@ -332,6 +332,23 @@ allocation policy for the internal shmem mount by using the kernel parameter
 seven valid policies for shmem (``always``, ``within_size``, ``advise``,
 ``never``, ``deny``, and ``force``).
 
+In the same manner as ``thp_anon`` controls each supported anonymous THP
+size, ``thp_shmem`` controls each supported shmem THP size. ``thp_shmem``
+has the same format as ``thp_anon``, but also supports the policy
+``within_size``.
+
+``thp_shmem=`` may be specified multiple times to configure all THP sizes
+as required. If ``thp_shmem=`` is specified at least once, any shmem THP
+sizes not explicitly configured on the command line are implicitly set to
+``never``.
+
+``transparent_hugepage_shmem`` setting only affects the global toggle. If
+``thp_shmem`` is not specified, PMD_ORDER hugepage will default to
+``inherit``. However, if a valid ``thp_shmem`` setting is provided by the
+user, the PMD_ORDER hugepage policy will be overridden. If the policy for
+PMD_ORDER is not defined within a valid ``thp_shmem``, its policy will
+default to ``never``.
+
 Hugepages in tmpfs/shmem
 ========================
 
diff --git a/mm/shmem.c b/mm/shmem.c
index dfcc88ec6e34..d2bf98aece40 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -136,6 +136,7 @@ static unsigned long huge_shmem_orders_always __read_mostly;
 static unsigned long huge_shmem_orders_madvise __read_mostly;
 static unsigned long huge_shmem_orders_inherit __read_mostly;
 static unsigned long huge_shmem_orders_within_size __read_mostly;
+static bool shmem_orders_configured __initdata;
 #endif
 
 #ifdef CONFIG_TMPFS
@@ -5027,7 +5028,8 @@ void __init shmem_init(void)
 	 * Default to setting PMD-sized THP to inherit the global setting and
 	 * disable all other multi-size THPs.
 	 */
-	huge_shmem_orders_inherit = BIT(HPAGE_PMD_ORDER);
+	if (!shmem_orders_configured)
+		huge_shmem_orders_inherit = BIT(HPAGE_PMD_ORDER);
 #endif
 	return;
 
@@ -5195,6 +5197,107 @@ static int __init setup_transparent_hugepage_shmem(char *str)
 }
 __setup("transparent_hugepage_shmem=", setup_transparent_hugepage_shmem);
 
+static char str_dup[PAGE_SIZE] __initdata;
+static int __init setup_thp_shmem(char *str)
+{
+	char *token, *range, *policy, *subtoken;
+	unsigned long always, inherit, madvise, within_size;
+	char *start_size, *end_size;
+	int start, end, nr;
+	char *p;
+
+	if (!str || strlen(str) + 1 > PAGE_SIZE)
+		goto err;
+	strscpy(str_dup, str);
+
+	always = huge_shmem_orders_always;
+	inherit = huge_shmem_orders_inherit;
+	madvise = huge_shmem_orders_madvise;
+	within_size = huge_shmem_orders_within_size;
+	p = str_dup;
+	while ((token = strsep(&p, ";")) != NULL) {
+		range = strsep(&token, ":");
+		policy = token;
+
+		if (!policy)
+			goto err;
+
+		while ((subtoken = strsep(&range, ",")) != NULL) {
+			if (strchr(subtoken, '-')) {
+				start_size = strsep(&subtoken, "-");
+				end_size = subtoken;
+
+				start = get_order_from_str(start_size,
+							   THP_ORDERS_ALL_FILE_DEFAULT);
+				end = get_order_from_str(end_size,
+							 THP_ORDERS_ALL_FILE_DEFAULT);
+			} else {
+				start_size = end_size = subtoken;
+				start = end = get_order_from_str(subtoken,
+								 THP_ORDERS_ALL_FILE_DEFAULT);
+			}
+
+			if (start == -EINVAL) {
+				pr_err("invalid size %s in thp_shmem boot parameter\n",
+				       start_size);
+				goto err;
+			}
+
+			if (end == -EINVAL) {
+				pr_err("invalid size %s in thp_shmem boot parameter\n",
+				       end_size);
+				goto err;
+			}
+
+			if (start < 0 || end < 0 || start > end)
+				goto err;
+
+			nr = end - start + 1;
+			if (!strcmp(policy, "always")) {
+				bitmap_set(&always, start, nr);
+				bitmap_clear(&inherit, start, nr);
+				bitmap_clear(&madvise, start, nr);
+				bitmap_clear(&within_size, start, nr);
+			} else if (!strcmp(policy, "advise")) {
+				bitmap_set(&madvise, start, nr);
+				bitmap_clear(&inherit, start, nr);
+				bitmap_clear(&always, start, nr);
+				bitmap_clear(&within_size, start, nr);
+			} else if (!strcmp(policy, "inherit")) {
+				bitmap_set(&inherit, start, nr);
+				bitmap_clear(&madvise, start, nr);
+				bitmap_clear(&always, start, nr);
+				bitmap_clear(&within_size, start, nr);
+			} else if (!strcmp(policy, "within_size")) {
+				bitmap_set(&within_size, start, nr);
+				bitmap_clear(&inherit, start, nr);
+				bitmap_clear(&madvise, start, nr);
+				bitmap_clear(&always, start, nr);
+			} else if (!strcmp(policy, "never")) {
+				bitmap_clear(&inherit, start, nr);
+				bitmap_clear(&madvise, start, nr);
+				bitmap_clear(&always, start, nr);
+				bitmap_clear(&within_size, start, nr);
+			} else {
+				pr_err("invalid policy %s in thp_shmem boot parameter\n", policy);
+				goto err;
+			}
+		}
+	}
+
+	huge_shmem_orders_always = always;
+	huge_shmem_orders_madvise = madvise;
+	huge_shmem_orders_inherit = inherit;
+	huge_shmem_orders_within_size = within_size;
+	shmem_orders_configured = true;
+	return 1;
+
+err:
+	pr_warn("thp_shmem=%s: error parsing string, ignoring setting\n", str);
+	return 0;
+}
+__setup("thp_shmem=", setup_thp_shmem);
+
 #endif /* CONFIG_TRANSPARENT_HUGEPAGE */
 
 #else /* !CONFIG_SHMEM */
-- 
2.46.2

Re: [PATCH v5 4/5] mm: shmem: override mTHP shmem default with a kernel parameter

[Baolin Wang]

On 2024/11/2 00:54, Maíra Canal wrote:
> Add the ``thp_shmem=`` kernel command line to allow specifying the
> default policy of each supported shmem hugepage size. The kernel parameter
> accepts the following format:
> 
> thp_shmem=<size>[KMG],<size>[KMG]:<policy>;<size>[KMG]-<size>[KMG]:<policy>
> 
> For example,
> 
> thp_shmem=16K-64K:always;128K,512K:inherit;256K:advise;1M-2M:never;4M-8M:within_size
> 
> Some GPUs may benefit from using huge pages. Since DRM GEM uses shmem
> to allocate anonymous pageable memory, it’s essential to control the huge
> page allocation policy for the internal shmem mount. This control can be
> achieved through the ``transparent_hugepage_shmem=`` parameter.
> 
> Beyond just setting the allocation policy, it’s crucial to have granular
> control over the size of huge pages that can be allocated. The GPU may
> support only specific huge page sizes, and allocating pages larger/smaller
> than those sizes would be ineffective.
> 
> Signed-off-by: Maíra Canal <mcanal@igalia.com>
> ---
>   .../admin-guide/kernel-parameters.txt         |  10 ++
>   Documentation/admin-guide/mm/transhuge.rst    |  17 +++
>   mm/shmem.c                                    | 105 +++++++++++++++++-
>   3 files changed, 131 insertions(+), 1 deletion(-)
> 
> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> index acabb04d0dd4..b48d744d99b0 100644
> --- a/Documentation/admin-guide/kernel-parameters.txt
> +++ b/Documentation/admin-guide/kernel-parameters.txt
> @@ -6700,6 +6700,16 @@
>   			Force threading of all interrupt handlers except those
>   			marked explicitly IRQF_NO_THREAD.
>   
> +	thp_shmem=	[KNL]
> +			Format: <size>[KMG],<size>[KMG]:<policy>;<size>[KMG]-<size>[KMG]:<policy>
> +			Control the default policy of each hugepage size for the
> +			internal shmem mount. <policy> is one of policies available
> +			for the shmem mount ("always", "inherit", "never", "within_size",
> +			and "advise").
> +			It can be used multiple times for multiple shmem THP sizes.
> +			See Documentation/admin-guide/mm/transhuge.rst for more
> +			details.
> +
>   	topology=	[S390,EARLY]
>   			Format: {off | on}
>   			Specify if the kernel should make use of the cpu
> diff --git a/Documentation/admin-guide/mm/transhuge.rst b/Documentation/admin-guide/mm/transhuge.rst
> index 9c6f6da612c4..5034915f4e8e 100644
> --- a/Documentation/admin-guide/mm/transhuge.rst
> +++ b/Documentation/admin-guide/mm/transhuge.rst
> @@ -332,6 +332,23 @@ allocation policy for the internal shmem mount by using the kernel parameter
>   seven valid policies for shmem (``always``, ``within_size``, ``advise``,
>   ``never``, ``deny``, and ``force``).
>   
> +In the same manner as ``thp_anon`` controls each supported anonymous THP
> +size, ``thp_shmem`` controls each supported shmem THP size. ``thp_shmem``
> +has the same format as ``thp_anon``, but also supports the policy
> +``within_size``.
> +
> +``thp_shmem=`` may be specified multiple times to configure all THP sizes
> +as required. If ``thp_shmem=`` is specified at least once, any shmem THP
> +sizes not explicitly configured on the command line are implicitly set to
> +``never``.
> +
> +``transparent_hugepage_shmem`` setting only affects the global toggle. If
> +``thp_shmem`` is not specified, PMD_ORDER hugepage will default to
> +``inherit``. However, if a valid ``thp_shmem`` setting is provided by the
> +user, the PMD_ORDER hugepage policy will be overridden. If the policy for
> +PMD_ORDER is not defined within a valid ``thp_shmem``, its policy will
> +default to ``never``.
> +
>   Hugepages in tmpfs/shmem
>   ========================
>   
> diff --git a/mm/shmem.c b/mm/shmem.c
> index dfcc88ec6e34..d2bf98aece40 100644
> --- a/mm/shmem.c
> +++ b/mm/shmem.c
> @@ -136,6 +136,7 @@ static unsigned long huge_shmem_orders_always __read_mostly;
>   static unsigned long huge_shmem_orders_madvise __read_mostly;
>   static unsigned long huge_shmem_orders_inherit __read_mostly;
>   static unsigned long huge_shmem_orders_within_size __read_mostly;
> +static bool shmem_orders_configured __initdata;
>   #endif
>   
>   #ifdef CONFIG_TMPFS
> @@ -5027,7 +5028,8 @@ void __init shmem_init(void)
>   	 * Default to setting PMD-sized THP to inherit the global setting and
>   	 * disable all other multi-size THPs.
>   	 */
> -	huge_shmem_orders_inherit = BIT(HPAGE_PMD_ORDER);
> +	if (!shmem_orders_configured)
> +		huge_shmem_orders_inherit = BIT(HPAGE_PMD_ORDER);
>   #endif
>   	return;
>   
> @@ -5195,6 +5197,107 @@ static int __init setup_transparent_hugepage_shmem(char *str)
>   }
>   __setup("transparent_hugepage_shmem=", setup_transparent_hugepage_shmem);
>   
> +static char str_dup[PAGE_SIZE] __initdata;
> +static int __init setup_thp_shmem(char *str)
> +{
> +	char *token, *range, *policy, *subtoken;
> +	unsigned long always, inherit, madvise, within_size;
> +	char *start_size, *end_size;
> +	int start, end, nr;
> +	char *p;
> +
> +	if (!str || strlen(str) + 1 > PAGE_SIZE)
> +		goto err;
> +	strscpy(str_dup, str);
> +
> +	always = huge_shmem_orders_always;
> +	inherit = huge_shmem_orders_inherit;
> +	madvise = huge_shmem_orders_madvise;
> +	within_size = huge_shmem_orders_within_size;
> +	p = str_dup;
> +	while ((token = strsep(&p, ";")) != NULL) {
> +		range = strsep(&token, ":");
> +		policy = token;
> +
> +		if (!policy)
> +			goto err;
> +
> +		while ((subtoken = strsep(&range, ",")) != NULL) {
> +			if (strchr(subtoken, '-')) {
> +				start_size = strsep(&subtoken, "-");
> +				end_size = subtoken;
> +
> +				start = get_order_from_str(start_size,
> +							   THP_ORDERS_ALL_FILE_DEFAULT);
> +				end = get_order_from_str(end_size,
> +							 THP_ORDERS_ALL_FILE_DEFAULT);
> +			} else {
> +				start_size = end_size = subtoken;
> +				start = end = get_order_from_str(subtoken,
> +								 THP_ORDERS_ALL_FILE_DEFAULT);
> +			}
> +
> +			if (start == -EINVAL) {
> +				pr_err("invalid size %s in thp_shmem boot parameter\n",
> +				       start_size);
> +				goto err;
> +			}
> +
> +			if (end == -EINVAL) {
> +				pr_err("invalid size %s in thp_shmem boot parameter\n",
> +				       end_size);
> +				goto err;
> +			}

I have the same feeling that these are redundant checks. Otherwise look 
good to me.
Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>

[PATCH v5 5/5] mm: huge_memory: Use strscpy() instead of strcpy()

[Maíra Canal]

Replace strcpy() with strscpy() in mm/huge_memory.c

strcpy() has been deprecated because it is generally unsafe, so help to
eliminate it from the kernel source.

Link: https://github.com/KSPP/linux/issues/88
Signed-off-by: Maíra Canal <mcanal@igalia.com>
Reviewed-by: Lance Yang <ioworker0@gmail.com>
---
 mm/huge_memory.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index a6edbd8c4f49..1ebe18ec4560 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -969,7 +969,7 @@ static int __init setup_thp_anon(char *str)
 
 	if (!str || strlen(str) + 1 > PAGE_SIZE)
 		goto err;
-	strcpy(str_dup, str);
+	strscpy(str_dup, str);
 
 	always = huge_anon_orders_always;
 	madvise = huge_anon_orders_madvise;
@@ -4167,7 +4167,7 @@ static ssize_t split_huge_pages_write(struct file *file, const char __user *buf,
 
 		tok = strsep(&buf, ",");
 		if (tok) {
-			strcpy(file_path, tok);
+			strscpy(file_path, tok);
 		} else {
 			ret = -EINVAL;
 			goto out;
-- 
2.46.2

Re: [PATCH v5 0/5] mm: add more kernel parameters to control mTHP

[Andrew Morton]

On Fri,  1 Nov 2024 13:54:04 -0300 Maíra Canal <mcanal@igalia.com> wrote:

> This series introduces four patches related to the kernel parameters
> controlling mTHP and a fifth patch replacing `strcpy()` for `strscpy()`
> in the file `mm/huge_memory.c`.

Thanks.  I extracted [1/1] from the series, as the first patch is
6.12-rcX material.