kmalloc_cachealign: Utilize kmalloc() chunk size aligned property

Avoid power-of-2 rounding up if the to-be-used zone is already
aligned properly.

Suggested-by: dillon@

diff --git a/sys/kern/kern_slaballoc.c b/sys/kern/kern_slaballoc.c
index 48cc760..362092f 100644 (file)
--- a/sys/kern/kern_slaballoc.c
+++ b/sys/kern/kern_slaballoc.c
@@ -1602,7 +1602,28 @@ void *
 kmalloc_cachealign(unsigned long size_alloc, struct malloc_type *type,
     int flags)
 {
+#if (__VM_CACHELINE_SIZE == 32)
+#define CAN_CACHEALIGN(sz)     ((sz) >= 256)
+#elif (__VM_CACHELINE_SIZE == 64)
+#define CAN_CACHEALIGN(sz)     ((sz) >= 512)
+#elif (__VM_CACHELINE_SIZE == 128)
+#define CAN_CACHEALIGN(sz)     ((sz) >= 1024)
+#else
+#error "unsupported cacheline size"
+#endif
+
+       void *ret;
+
        if (size_alloc < __VM_CACHELINE_SIZE)
                size_alloc = __VM_CACHELINE_SIZE;
-       return kmalloc(size_alloc, type, flags | M_POWEROF2);
+       else if (!CAN_CACHEALIGN(size_alloc))
+               flags |= M_POWEROF2;
+
+       ret = kmalloc(size_alloc, type, flags);
+       KASSERT(((uintptr_t)ret & (__VM_CACHELINE_SIZE - 1)) == 0,
+           ("%p(%lu) not cacheline %d aligned",
+            ret, size_alloc, __VM_CACHELINE_SIZE));
+       return ret;
+
+#undef CAN_CACHEALIGN
 }