When handle dirty log, we face qemu_real_host_page_size and
TARGET_PAGE_SIZE. The first one is the granule of KVM dirty
bitmap, and the second one is the granule of QEMU dirty bitmap.
Generally speaking, qemu_real_host_page_size >= TARGET_PAGE_SIZE,
so misuse TARGET_PAGE_SIZE to init kvmslot dirty_bmap may waste
memory. For example, when qemu_real_host_page_size is 64K and
TARGET_PAGE_SIZE is 4K, this bugfix can save 93.75% memory.
Signed-off-by: Keqian Zhu <zhukeqi...@huawei.com>
---
accel/kvm/kvm-all.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)
diff --git a/accel/kvm/kvm-all.c b/accel/kvm/kvm-all.c
index baaa54249d..c5e06288eb 100644
--- a/accel/kvm/kvm-all.c
+++ b/accel/kvm/kvm-all.c
@@ -620,8 +620,12 @@ static void kvm_memslot_init_dirty_bitmap(KVMSlot *mem)
* too, in most cases).
* So for now, let's align to 64 instead of HOST_LONG_BITS here, in
* a hope that sizeof(long) won't become >8 any time soon.
+ *
+ * Note: the granule of kvm dirty log is qemu_real_host_page_size.
+ * And mem->memory_size is aligned to it (otherwise this mem can't
+ * be registered to KVM).
*/
- hwaddr bitmap_size = ALIGN(((mem->memory_size) >> TARGET_PAGE_BITS),
+ hwaddr bitmap_size = ALIGN(mem->memory_size / qemu_real_host_page_size,
/*HOST_LONG_BITS*/ 64) / 8;
mem->dirty_bmap = g_malloc0(bitmap_size);
}
--
2.23.0
