Hi David,
On 31/10/24 09:57, David Hildenbrand wrote:
On 31.10.24 13:51, Maíra Canal wrote:
Hi David,
On 31/10/24 09:37, David Hildenbrand wrote:
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/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.
Can I use functions from mm/huge_memory.c here?
Yes, that's the idea.
Unfortunately, it isn't possible without adding the function to a
header.
I deleted `get_order_from_str()` from mm/shmem.c just to test it:
mm/shmem.c:5230:13: error: call to undeclared function
'get_order_from_str'; ISO C99 and later do not support implicit function
declarations [-Wimplicit-function-declaration]
5230 | start =
get_order_from_str(start_size);
| ^
mm/shmem.c:5233:19: error: call to undeclared function
'get_order_from_str'; ISO C99 and later do not support implicit function
declarations [-Wimplicit-function-declaration]
5233 | start = end =
get_order_from_str(subtoken);
| ^
2 errors generated.
make[3]: *** [scripts/Makefile.build:229: mm/shmem.o] Error 1
make[2]: *** [scripts/Makefile.build:478: mm] Error 2
make[2]: *** Waiting for unfinished jobs....
Please, check the discussion I had with Barry about the pros and cons of
copy and paste and code refactor [1][2]. We ended up deciding to
duplicate the code.
[1]
https://lore.kernel.org/linux-mm/CAGsJ_4wJ2xoNRLMNkmLL3x1t2YiqQJ1=saXa+HNxRUbSNivRCw@xxxxxxxxxxxxxx/
[2]
https://lore.kernel.org/linux-mm/CAGsJ_4yp89one_hoB_87poU2wrpJh_0NVicRKW538eE6yo1kZw@xxxxxxxxxxxxxx/
Best Regards,
- Maíra
