Re: [PATCH v4] mm: Override mTHP "enabled" defaults at kernel cmdline
From: Baolin Wang
Date: Wed Aug 14 2024 - 03:53:51 EST
On 2024/8/14 10:02, Barry Song wrote:
From: Ryan Roberts <ryan.roberts@xxxxxxx>
Add thp_anon= cmdline parameter to allow specifying the default
enablement of each supported anon THP size. The parameter accepts the
following format and can be provided multiple times to configure each
size:
thp_anon=<size>,<size>[KMG]:<value>;<size>-<size>[KMG]:<value>
An example:
thp_anon=16K-64K:always;128K,512K:inherit;256K:madvise;1M-2M:never
See Documentation/admin-guide/mm/transhuge.rst for more details.
Configuring the defaults at boot time is useful to allow early user
space to take advantage of mTHP before its been configured through
sysfs.
Signed-off-by: Ryan Roberts <ryan.roberts@xxxxxxx>
Co-developed-by: Barry Song <v-songbaohua@xxxxxxxx>
Signed-off-by: Barry Song <v-songbaohua@xxxxxxxx>
LGTM. Feel free to add:
Reviewed-by: Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx>
Tested-by: Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx>
Just a small nit as below.
---
-v4:
* use bitmap APIs to set and clear bits. thanks very much for
David's comment!
.../admin-guide/kernel-parameters.txt | 9 ++
Documentation/admin-guide/mm/transhuge.rst | 37 +++++--
mm/huge_memory.c | 96 ++++++++++++++++++-
3 files changed, 134 insertions(+), 8 deletions(-)
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index f0057bac20fb..d0d141d50638 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -6629,6 +6629,15 @@
<deci-seconds>: poll all this frequency
0: no polling (default)
+ thp_anon= [KNL]
+ Format: <size>,<size>[KMG]:<state>;<size>-<size>[KMG]:<state>
+ state is one of "always", "madvise", "never" or "inherit".
+ Can be used to control the default behavior of the
+ system with respect to anonymous transparent hugepages.
+ Can be used multiple times for multiple anon THP sizes.
+ See Documentation/admin-guide/mm/transhuge.rst for more
+ details.
+
threadirqs [KNL,EARLY]
Force threading of all interrupt handlers except those
marked explicitly IRQF_NO_THREAD.
diff --git a/Documentation/admin-guide/mm/transhuge.rst b/Documentation/admin-guide/mm/transhuge.rst
index 7072469de8a8..528e1a19d63f 100644
--- a/Documentation/admin-guide/mm/transhuge.rst
+++ b/Documentation/admin-guide/mm/transhuge.rst
@@ -284,13 +284,36 @@ that THP is shared. Exceeding the number would block the collapse::
A higher value may increase memory footprint for some workloads.
-Boot parameter
-==============
-
-You can change the sysfs boot time defaults of Transparent Hugepage
-Support by passing the parameter ``transparent_hugepage=always`` or
-``transparent_hugepage=madvise`` or ``transparent_hugepage=never``
-to the kernel command line.
+Boot parameters
+===============
+
+You can change the sysfs boot time default for the top-level "enabled"
+control by passing the parameter ``transparent_hugepage=always`` or
+``transparent_hugepage=madvise`` or ``transparent_hugepage=never`` to the
+kernel command line.
+
+Alternatively, each supported anonymous THP size can be controlled by
+passing ``thp_anon=<size>,<size>[KMG]:<state>;<size>-<size>[KMG]:<state>``,
+where ``<size>`` is the THP size and ``<state>`` is one of ``always``,
+``madvise``, ``never`` or ``inherit``.
+
+For example, the following will set 16K, 32K, 64K THP to ``always``,
+set 128K, 512K to ``inherit``, set 256K to ``madvise`` and 1M, 2M
+to ``never``::
+
+ thp_anon=16K-64K:always;128K,512K:inherit;256K:madvise;1M-2M:never
+
+``thp_anon=`` may be specified multiple times to configure all THP sizes as
+required. If ``thp_anon=`` is specified at least once, any anon THP sizes
+not explicitly configured on the command line are implicitly set to
+``never``.
+
+``transparent_hugepage`` setting only affects the global toggle. If
+``thp_anon`` is not specified, PMD_ORDER THP will default to ``inherit``.
+However, if a valid ``thp_anon`` setting is provided by the user, the
+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``.
Hugepages in tmpfs/shmem
========================
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 1a12c011e2df..c5f4e97b49de 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -81,6 +81,7 @@ unsigned long huge_zero_pfn __read_mostly = ~0UL;
unsigned long huge_anon_orders_always __read_mostly;
unsigned long huge_anon_orders_madvise __read_mostly;
unsigned long huge_anon_orders_inherit __read_mostly;
+static bool anon_orders_configured;
unsigned long __thp_vma_allowable_orders(struct vm_area_struct *vma,
unsigned long vm_flags,
@@ -737,7 +738,10 @@ static int __init hugepage_init_sysfs(struct kobject **hugepage_kobj)
* disable all other sizes. powerpc's PMD_ORDER isn't a compile-time
* constant so we have to do this here.
*/
- huge_anon_orders_inherit = BIT(PMD_ORDER);
+ if (!anon_orders_configured) {
+ huge_anon_orders_inherit = BIT(PMD_ORDER);
+ anon_orders_configured = true;
+ }
*hugepage_kobj = kobject_create_and_add("transparent_hugepage", mm_kobj);
if (unlikely(!*hugepage_kobj)) {
@@ -922,6 +926,96 @@ 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);
+ order = fls(size >> PAGE_SHIFT) - 1;
Nit: using get_order() seems more robust?
+ if ((1 << order) & ~THP_ORDERS_ALL_ANON) {
+ pr_err("invalid size %s(order %d) in thp_anon boot parameter\n",
+ size_str, order);
+ return -EINVAL;
+ }
+
+ return order;
+}
[snip]