Adds sysctl "vm.warn_high_order". If set it will warn about
allocations with order >= vm.warn_high_order.
Prints only 32 warnings at most and skips all __GFP_NOWARN allocations.
The code is under config option, disabled by default.
If enabled, default vm.warn_high_order is 3 (PAGE_ALLOC_COSTLY_ORDER).
Sysctl max value is set to 100 which should be enough to exceed maximum
order (normally MAX_ORDER == 11).
Signed-off-by: Konstantin Khorenko <khorenko@xxxxxxxxxxxxx>
---
kernel/sysctl.c | 15 +++++++++++++++
mm/Kconfig | 18 ++++++++++++++++++
mm/page_alloc.c | 25 +++++++++++++++++++++++++
3 files changed, 58 insertions(+)
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 5fc724e4e454..28a8ebfa7a1d 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -176,6 +176,10 @@ extern int unaligned_dump_stack;
extern int no_unaligned_warning;
#endif
+#ifdef CONFIG_WARN_HIGH_ORDER
+extern int warn_order;
+#endif
+
#ifdef CONFIG_PROC_SYSCTL
/**
@@ -1675,6 +1679,17 @@ static struct ctl_table vm_table[] = {
.extra1 = (void *)&mmap_rnd_compat_bits_min,
.extra2 = (void *)&mmap_rnd_compat_bits_max,
},
+#endif
+#ifdef CONFIG_WARN_HIGH_ORDER
+ {
+ .procname = "warn_high_order",
+ .data = &warn_order,
+ .maxlen = sizeof(warn_order),
+ .mode = 0644,
+ .proc_handler = proc_dointvec_minmax,
+ .extra1 = &zero,
+ .extra2 = &one_hundred,
+ },
#endif
{ }
};
diff --git a/mm/Kconfig b/mm/Kconfig
index d85e39da47ae..4e2d613d52f1 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -336,6 +336,24 @@ config MEMORY_FAILURE
even when some of its memory has uncorrected errors. This requires
special hardware support and typically ECC memory.
+config WARN_HIGH_ORDER
+ bool "Enable complains about high order memory allocations"
+ depends on !LOCKDEP
+ default n
+ help
+ Enables warnings on high order memory allocations. This allows to
+ determine users of large memory chunks and rework them to decrease
+ allocation latency. Note, some debug options make kernel structures
+ fat.
+
+config WARN_HIGH_ORDER_LEVEL
+ int "Define page order level considered as too high"
+ depends on WARN_HIGH_ORDER
+ default 3
+ help
+ Defines page order starting which the system to complain about.
+ Default is current PAGE_ALLOC_COSTLY_ORDER.
+
config HWPOISON_INJECT
tristate "HWPoison pages injector"
depends on MEMORY_FAILURE && DEBUG_KERNEL && PROC_FS
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index e95b5b7c9c3d..258892adb861 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -4341,6 +4341,30 @@ static inline void finalise_ac(gfp_t gfp_mask, struct alloc_context *ac)
ac->high_zoneidx, ac->nodemask);
}
+#ifdef CONFIG_WARN_HIGH_ORDER
+int warn_order = CONFIG_WARN_HIGH_ORDER_LEVEL;
+
+/*
+ * Complain if we allocate a high order page unless there is a __GFP_NOWARN
+ * flag provided.
+ *
+ * Shuts up after 32 complains.
+ */
+static __always_inline void warn_high_order(int order, gfp_t gfp_mask)
+{
+ static atomic_t warn_count = ATOMIC_INIT(32);
+
+ if (order >= warn_order && !(gfp_mask & __GFP_NOWARN))
+ WARN(atomic_dec_if_positive(&warn_count) >= 0,
+ "order %d >= %d, gfp 0x%x\n",
+ order, warn_order, gfp_mask);
+}
+#else
+static __always_inline void warn_high_order(int order, gfp_t gfp_mask)
+{
+}
+#endif
+
/*
* This is the 'heart' of the zoned buddy allocator.
*/
@@ -4361,6 +4385,7 @@ __alloc_pages_nodemask(gfp_t gfp_mask, unsigned int order, int preferred_nid,
WARN_ON_ONCE(!(gfp_mask & __GFP_NOWARN));
return NULL;
}
+ warn_high_order(order, gfp_mask);
gfp_mask &= gfp_allowed_mask;
alloc_mask = gfp_mask;
--
2.15.1
