[PATCH] percpu: convert free page float to bytes

[Dennis Zhou]

The percpu memory allocator keeps around a minimum number of free pages
to ensure we can satisfy atomic allocations. However, we've always kept
this number in terms of pages. On certain architectures like arm and
powerpc, the default page size could be 64k instead of 4k. So, start
with a target number of free bytes and then convert to pages.

Signed-off-by: Dennis Zhou <dennis@xxxxxxxxxx>
---
 mm/percpu.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/mm/percpu.c b/mm/percpu.c
index ba13e683d022..287fe3091244 100644
--- a/mm/percpu.c
+++ b/mm/percpu.c
@@ -80,6 +80,7 @@
 #include <linux/mutex.h>
 #include <linux/percpu.h>
 #include <linux/pfn.h>
+#include <linux/sizes.h>
 #include <linux/slab.h>
 #include <linux/spinlock.h>
 #include <linux/vmalloc.h>
@@ -107,11 +108,12 @@
 /* chunks in slots below this are subject to being sidelined on failed alloc */
 #define PCPU_SLOT_FAIL_THRESHOLD	3
 
-#define PCPU_EMPTY_POP_PAGES_LOW	2
-#define PCPU_EMPTY_POP_PAGES_HIGH	4
+#define PCPU_EMPTY_POP_PAGES_LOW	(max_t(int, (SZ_8K) / PAGE_SIZE, 1))
+#define PCPU_EMPTY_POP_PAGES_HIGH	(max_t(int, (SZ_16K) / PAGE_SIZE, \
+					       PCPU_EMPTY_POP_PAGES_LOW + 1))
 
 /* only schedule reclaim if there are at least N empty pop pages sidelined */
-#define PCPU_EMPTY_POP_RECLAIM_THRESHOLD	4
+#define PCPU_EMPTY_POP_RECLAIM_THRESHOLD	(PCPU_EMPTY_POP_PAGES_HIGH)
 
 #ifdef CONFIG_SMP
 /* default addr <-> pcpu_ptr mapping, override in asm/percpu.h if necessary */
-- 
2.31.1.368.gbe11c130af-goog