On 30.10.24 13:58, 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
By configuring the default policy of several shmem hugepages, the user
can take advantage of mTHP before it's been configured through sysfs.
Signed-off-by: Maíra Canal <mcanal@xxxxxxxxxx>
---
.../admin-guide/kernel-parameters.txt | 10 ++
Documentation/admin-guide/mm/transhuge.rst | 17 +++
mm/shmem.c | 109 +++++++++++++++++-
3 files changed, 135 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 9b5b02c4d1ab..47e7fc30e22d 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..c2299fa0b345 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;
@@ -5180,6 +5182,26 @@ struct kobj_attribute thpsize_shmem_enabled_attr =
#if defined(CONFIG_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_FILE_DEFAULT)
+ goto err;
+
+ return order;
+err:
+ pr_err("invalid size %s in thp_shmem boot parameter\n", size_str);
+ return -EINVAL;
+}
Hm, mostly copy and paste. You could reuse existing get_order_from_str()
simply by passing in the supported orders and moving error reporting to
the caller.
static inline int get_order_from_str(const char *size_str,
int valid_orders)
{
...
if (!is_power_of_2(size))
return -EINVAL;
order = get_order(size);
if (BIT(order) & ~valid_orders)
return -EINVAL;
return order;
}
+
static int __init setup_transparent_hugepage_shmem(char *str)
{
int huge;
@@ -5195,6 +5217,91 @@ 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);
+ end = get_order_from_str(end_size);
+ } else {
+ start = end = get_order_from_str(subtoken);
+ }
+
+ 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;
+ }
+ }
+ }
Similarly, copy-paste. But not that easy to abstract :) So maybe we'll
have to keep that as is for now.
--
Cheers,
David / dhildenb
