* Peter Xu (pet...@redhat.com) wrote:
> When synchronizing dirty bitmap from kernel KVM we do it in a
> per-kvmslot fashion and we allocate the userspace bitmap for each of
> the ioctl. This patch instead make the bitmap cache be persistent
> then we don't need to g_malloc0() every time.
>
> More importantly, the cached per-kvmslot dirty bitmap will be further
> used when we want to add support for the KVM_CLEAR_DIRTY_LOG and this
> cached bitmap will be used to guarantee we won't clear any unknown
> dirty bits otherwise that can be a severe data loss issue for
> migration code.
>
> Signed-off-by: Peter Xu <pet...@redhat.com>
OK, so this will use a little more memory, but probably fragment stuff
less.
Reviewed-by: Dr. David Alan Gilbert <dgilb...@redhat.com>
> ---
> accel/kvm/kvm-all.c | 10 +++++++---
> include/sysemu/kvm_int.h | 2 ++
> 2 files changed, 9 insertions(+), 3 deletions(-)
>
> diff --git a/accel/kvm/kvm-all.c b/accel/kvm/kvm-all.c
> index b686531586..9fb0694772 100644
> --- a/accel/kvm/kvm-all.c
> +++ b/accel/kvm/kvm-all.c
> @@ -511,17 +511,19 @@ static int
> kvm_physical_sync_dirty_bitmap(KVMMemoryListener *kml,
> */
> size = ALIGN(((mem->memory_size) >> TARGET_PAGE_BITS),
> /*HOST_LONG_BITS*/ 64) / 8;
> - d.dirty_bitmap = g_malloc0(size);
> + if (!mem->dirty_bmap) {
> + /* Allocate on the first log_sync, once and for all */
> + mem->dirty_bmap = g_malloc0(size);
> + }
>
> + d.dirty_bitmap = mem->dirty_bmap;
> d.slot = mem->slot | (kml->as_id << 16);
> if (kvm_vm_ioctl(s, KVM_GET_DIRTY_LOG, &d) == -1) {
> DPRINTF("ioctl failed %d\n", errno);
> - g_free(d.dirty_bitmap);
> return -1;
> }
>
> kvm_get_dirty_pages_log_range(section, d.dirty_bitmap);
> - g_free(d.dirty_bitmap);
> }
>
> return 0;
> @@ -796,6 +798,8 @@ static void kvm_set_phys_mem(KVMMemoryListener *kml,
> }
>
> /* unregister the slot */
> + g_free(mem->dirty_bmap);
> + mem->dirty_bmap = NULL;
> mem->memory_size = 0;
> mem->flags = 0;
> err = kvm_set_user_memory_region(kml, mem, false);
> diff --git a/include/sysemu/kvm_int.h b/include/sysemu/kvm_int.h
> index f838412491..687a2ee423 100644
> --- a/include/sysemu/kvm_int.h
> +++ b/include/sysemu/kvm_int.h
> @@ -21,6 +21,8 @@ typedef struct KVMSlot
> int slot;
> int flags;
> int old_flags;
> + /* Dirty bitmap cache for the slot */
> + unsigned long *dirty_bmap;
> } KVMSlot;
>
> typedef struct KVMMemoryListener {
> --
> 2.17.1
>
--
Dr. David Alan Gilbert / dgilb...@redhat.com / Manchester, UK
