Messages in this thread | | | Date | Thu, 15 Oct 2020 18:00:09 +0800 | From | Wei Yang <> | Subject | Re: [PATCH v1 02/29] virtio-mem: simplify calculation in virtio_mem_mb_state_prepare_next_mb() |
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On Thu, Oct 15, 2020 at 10:00:15AM +0200, David Hildenbrand wrote: >On 15.10.20 06:02, Wei Yang wrote: >> On Mon, Oct 12, 2020 at 02:52:56PM +0200, David Hildenbrand wrote: >>> We actually need one byte less (next_mb_id is exclusive, first_mb_id is >>> inclusive). Simplify. >>> >>> Cc: "Michael S. Tsirkin" <mst@redhat.com> >>> Cc: Jason Wang <jasowang@redhat.com> >>> Cc: Pankaj Gupta <pankaj.gupta.linux@gmail.com> >>> Signed-off-by: David Hildenbrand <david@redhat.com> >>> --- >>> drivers/virtio/virtio_mem.c | 4 ++-- >>> 1 file changed, 2 insertions(+), 2 deletions(-) >>> >>> diff --git a/drivers/virtio/virtio_mem.c b/drivers/virtio/virtio_mem.c >>> index a1f5bf7a571a..670b3faf412d 100644 >>> --- a/drivers/virtio/virtio_mem.c >>> +++ b/drivers/virtio/virtio_mem.c >>> @@ -257,8 +257,8 @@ static enum virtio_mem_mb_state virtio_mem_mb_get_state(struct virtio_mem *vm, >>> */ >>> static int virtio_mem_mb_state_prepare_next_mb(struct virtio_mem *vm) >>> { >>> - unsigned long old_bytes = vm->next_mb_id - vm->first_mb_id + 1; >>> - unsigned long new_bytes = vm->next_mb_id - vm->first_mb_id + 2; >>> + unsigned long old_bytes = vm->next_mb_id - vm->first_mb_id; >>> + unsigned long new_bytes = old_bytes + 1; >> >> This is correct. >> >> So this looks more like a fix? > >We allocate an additional new page "one memory block too early". > >So we would allocate the first page for blocks 0..510, and already >allocate the second page with block 511, although we could have fit it >into the first page. Block 512 will then find that the second page is >already there and simply use the second page. > >So as we do it consistently, nothing will go wrong - that's why I >avoided using the "fix" terminology. >
Yes, my feeling is this is not a simplification. Instead this is a more precise calculation.
How about use this subject?
virtio-mem: more precise calculation in virtio_mem_mb_state_prepare_next_mb()
>Thanks! > >-- >Thanks, > >David / dhildenb
-- Wei Yang Help you, Help me
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