On 03.12.20 18:49, Vitaly Kuznetsov wrote: > David Hildenbrand <[email protected]> writes: > >> On 02.12.20 17:12, Vitaly Kuznetsov wrote: >>> Unlike virtio_balloon/virtio_mem/xen balloon drivers, Hyper-V balloon driver >>> does not adjust managed pages count when ballooning/un-ballooning and this >>> leads >>> to incorrect stats being reported, e.g. unexpected 'free' output. >>> >>> Note, the calculation in post_status() seems to remain correct: ballooned >>> out >>> pages are never 'available' and we manually add dm->num_pages_ballooned to >>> 'commited'. >>> >>> Suggested-by: David Hildenbrand <[email protected]> >>> Signed-off-by: Vitaly Kuznetsov <[email protected]> >>> --- >>> drivers/hv/hv_balloon.c | 5 ++++- >>> 1 file changed, 4 insertions(+), 1 deletion(-) >>> >>> diff --git a/drivers/hv/hv_balloon.c b/drivers/hv/hv_balloon.c >>> index da3b6bd2367c..8c471823a5af 100644 >>> --- a/drivers/hv/hv_balloon.c >>> +++ b/drivers/hv/hv_balloon.c >>> @@ -1198,6 +1198,7 @@ static void free_balloon_pages(struct >>> hv_dynmem_device *dm, >>> __ClearPageOffline(pg); >>> __free_page(pg); >>> dm->num_pages_ballooned--; >>> + adjust_managed_page_count(pg, 1); >>> } >>> } >>> >>> @@ -1238,8 +1239,10 @@ static unsigned int alloc_balloon_pages(struct >>> hv_dynmem_device *dm, >>> split_page(pg, get_order(alloc_unit << PAGE_SHIFT)); >>> >>> /* mark all pages offline */ >>> - for (j = 0; j < alloc_unit; j++) >>> + for (j = 0; j < alloc_unit; j++) { >>> __SetPageOffline(pg + j); >>> + adjust_managed_page_count(pg + j, -1); >>> + } >>> >>> bl_resp->range_count++; >>> bl_resp->range_array[i].finfo.start_page = >>> >> >> I assume this has been properly tested such that it does not change the >> system behavior regarding when/how HyperV decides to add/remove memory. >> > > I'm always reluctant to confirm 'proper testing' as no matter how small > and 'obvious' the change is, regressions keep happening :-) But yes, > this was tested on a Hyper-V host and 'stress' and I observed 'free' > when the balloon was both inflated and deflated, values looked sane.
That;s what I wanted to hear ;) -- Thanks, David / dhildenb
