(2010/10/31 3:28), Jesper Juhl wrote:
Hi,
We can improve kvm_vm_ioctl_get_dirty_log() slightly by using vzalloc()
rather than first allocating and then manually zero the memory with
memset(). Also, while I was looking at this I noticed that we assign
I personally prefer this new vzalloc() to vmalloc() + memset().
Just from my interest, is there real performance difference not just
the cleanup effect? If so, we'd better do this for other places too.
-ENOMEM to the 'r' variable twice even though none of the code inbetween
the two assignments can change 'r', so I removed the second assignment.
Patch has been compile tested only.
Please consider merging and please CC me on all replies as I'm not
subscribed to the kvm mailing list.
Signed-off-by: Jesper Juhl<jj@xxxxxxxxxxxxx>
---
x86.c | 4 +---
1 file changed, 1 insertion(+), 3 deletions(-)
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 2288ad8..29f9c0a 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -3174,12 +3174,10 @@ int kvm_vm_ioctl_get_dirty_log(struct kvm *kvm,
spin_unlock(&kvm->mmu_lock);
This patch is not based on kvm.git, I guess.
r = -ENOMEM;
- dirty_bitmap = vmalloc(n);
+ dirty_bitmap = vzalloc(n);
if (!dirty_bitmap)
goto out;
- memset(dirty_bitmap, 0, n);
- r = -ENOMEM;
This one is here because this belongs to a different code block from the
previous one. This keeps it easy to insert another codes in between these
two blocks. The optimization will be done at compile time.
IIRC, I did like this based on Avi's advise.
Takuya
slots = kzalloc(sizeof(struct kvm_memslots), GFP_KERNEL);
if (!slots) {
vfree(dirty_bitmap);
--
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