Re: [RFC 4/5] vmx_balloon: update the NR_BALLOON_PAGES state

On 12.03.25 21:11, Nico Pache wrote:

On Wed, Mar 12, 2025 at 12:57 AM Michael S. Tsirkin [off-list ref] wrote:

quoted

On Tue, Mar 11, 2025 at 06:06:59PM -0600, Nico Pache wrote:

quoted

Update the NR_BALLOON_PAGES counter when pages are added to or
removed from the VMware balloon.

Signed-off-by: Nico Pache <redacted>
---
  drivers/misc/vmw_balloon.c | 5 ++++-
  1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/misc/vmw_balloon.c b/drivers/misc/vmw_balloon.c
index c817d8c21641..2c70b08c6fb3 100644
--- a/drivers/misc/vmw_balloon.c
+++ b/drivers/misc/vmw_balloon.c

@@ -673,6 +673,8 @@ static int vmballoon_alloc_page_list(struct vmballoon *b,

                       vmballoon_stats_page_inc(b, VMW_BALLOON_PAGE_STAT_ALLOC,
                                                ctl->page_size);
+                     mod_node_page_state(page_pgdat(page), NR_BALLOON_PAGES,
+                             vmballoon_page_in_frames(ctl->page_size));

same issue as virtio I think - this counts frames not pages.

I agree with the viritio issue since PAGE_SIZE can be larger than
VIRTIO_BALLOON_PFN_SHIFT, resulting in multiple virtio_balloon pages
for each page. I fixed that one, thanks!

For the Vmware one, the code is littered with mentions of counting in
4k or 2M but as far as I can tell from looking at the code it actually
operates in PAGE_SIZE or PMD size chunks and this count would be
correct.
Perhaps I am missing something though.

vmballoon_page_in_frames() documents to "Return: the number of 4k frames.", because it supports either 4k or 2M chunks IIRC.

I think the catch is that PAGE_SIZE will in these configs always be 4k. Otherwise things like vmballoon_mark_page_offline() wouldn't work as expected.

So I think this is correct.

-- 
Cheers,

David / dhildenb