Introduce 2 ways to setup/configure "unlimited_slabs" tweak:
1. "slub.unlimited_slabs=" kernel boot option
* "slub.unlimited_slabs=1" to enable the tweak
* "slub.unlimited_slabs=0" to disable the tweak
2. /sys/kernel/debug/unlimited_slabs entry
* echo 1 > /sys/module/slub/parameters/unlimited_slabs to enable the tweak
* echo 0 > /sys/module/slub/parameters/unlimited_slabs to disable the tweak
The module parameter is BOOL, you can use [yYnN01] values.
The "unlimited_slabs" functionality is disabled by default.
Implementation details: static keys cannot be switched during kernel
boot option parsing, so the actual switch is delayed to late_init stage.
https://virtuozzo.atlassian.net/browse/PSBM-155867
Signed-off-by: Konstantin Khorenko <khore...@virtuozzo.com>
---
v2:
* static key renamed from "unlimited_slabs" to "unlimited_slabs_key"
* scheme of using __setup() for kernel boot option and manually created
debugfs entry has been substituted by module_param_cb() which automatically
creates debugfs entry for module parameter.
* kernel boot option changed from "unlimited_slabs" to "slub.unlimited_slabs"
as it's now module parameter
* the module parameter is BOOL, so [yYnN01] values can be used
* static keys cannot be switched during kernel boot option parsing, so the
actual switch is delayed to late_init stag
mm/slub.c | 57 ++++++++++++++++++++++++++++++++++++++++++++++++++++++-
1 file changed, 56 insertions(+), 1 deletion(-)
diff --git a/mm/slub.c b/mm/slub.c
index ea3e20e73fe6..cf3e8f759234 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -2466,6 +2466,58 @@ static inline void *get_freelist(struct kmem_cache *s,
struct page *page)
return freelist;
}
+struct static_key unlimited_slabs_key = STATIC_KEY_INIT_FALSE;
+
+static bool __read_mostly unlimited_slabs = false;
+static bool unlimited_slabs_boot = false;
+
+static int unlimited_slabs_set(const char *val, const struct kernel_param *kp);
+static const struct kernel_param_ops unlimited_slabs_ops = {
+ .set = unlimited_slabs_set,
+ .get = param_get_bool,
+};
+
+module_param_cb(unlimited_slabs, &unlimited_slabs_ops, &unlimited_slabs, 0644);
+__MODULE_PARM_TYPE(unlimited_slabs, "bool");
+MODULE_PARM_DESC(unlimited_slabs,
+ "SLABs marked with pf_memalloc flag ignore memcg limits");
+
+/*
+ * static_keys cannot be switched during early boot stage,
+ * so delay the setup till late_initcall
+ */
+static int __init unlimited_slabs_set_boot(void)
+{
+ if (unlimited_slabs_boot) {
+ static_key_slow_inc(&unlimited_slabs_key);
+ printk("unlimited_slabs tweak has been enabled "
+ "due to slub.unlimited_slabs=1 kernel boot option\n");
+ }
+ return 0;
+}
+late_initcall(unlimited_slabs_set_boot);
+
+static int unlimited_slabs_set(const char *val, const struct kernel_param *kp)
+{
+ /* One of =[yYnN01] */
+ if (strtobool(val, &unlimited_slabs) < 0)
+ return -EINVAL;
+
+ if (static_key_false(&unlimited_slabs_key) && !unlimited_slabs) {
+ static_key_slow_dec(&unlimited_slabs_key);
+ printk("unlimited_slabs tweak has been disabled\n");
+ } else if (!static_key_false(&unlimited_slabs_key) && unlimited_slabs) {
+ if (unlikely(system_state < SYSTEM_RUNNING))
+ unlimited_slabs_boot = true;
+ else {
+ static_key_slow_inc(&unlimited_slabs_key);
+ printk("unlimited_slabs tweak has been enabled\n");
+ }
+ }
+
+ return 0;
+}
+
/*
* Slow path. The lockless freelist is empty or we need to perform
* debugging duties.
@@ -2619,7 +2671,10 @@ static void *___slab_alloc_unlimited(struct kmem_cache
*s, gfp_t gfpflags, int n
static void *___slab_alloc(struct kmem_cache *s, gfp_t gfpflags, int node,
unsigned long addr, struct kmem_cache_cpu *c)
{
- return ___slab_alloc_unlimited(s, gfpflags, node, addr, c);
+ if (static_key_false(&unlimited_slabs_key))
+ return ___slab_alloc_unlimited(s, gfpflags, node, addr, c);
+ else
+ return ___slab_alloc_limited(s, gfpflags, node, addr, c);
}
/*
--
2.24.3
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