Re: [Qemu-devel] [PATCH 2/2] sheepdog: remove huge BSS object

["Philippe Mathieu-Daudé" <f4bug@amsat.org>]

On 05/22/2018 05:10 PM, Paolo Bonzini wrote:
> block/sheepdog.o has a 4M static variable that is 90% of QEMU's whole .bss
> section.  Replace it with a heap-allocated block, and make it smaller too
> since only the inode header is actually being used.
> 
> bss size goes down from 4464280 to 269976.

\o/

> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>

> ---
>  block/sheepdog.c | 21 +++++++++++----------
>  1 file changed, 11 insertions(+), 10 deletions(-)
> 
> diff --git a/block/sheepdog.c b/block/sheepdog.c
> index 23cf5a8430..2068166e3e 100644
> --- a/block/sheepdog.c
> +++ b/block/sheepdog.c
> @@ -2940,13 +2940,14 @@ static int sd_snapshot_list(BlockDriverState *bs, QEMUSnapshotInfo **psn_tab)
>      QEMUSnapshotInfo *sn_tab = NULL;
>      unsigned wlen, rlen;
>      int found = 0;
> -    static SheepdogInode inode;
> +    SheepdogInode *inode;
>      unsigned long *vdi_inuse;
>      unsigned int start_nr;
>      uint64_t hval;
>      uint32_t vid;
>  
>      vdi_inuse = g_malloc(max);
> +    inode = g_malloc(SD_INODE_HEADER_SIZE);
>  
>      fd = connect_to_sdog(s, &local_err);
>      if (fd < 0) {
> @@ -2989,7 +2990,7 @@ static int sd_snapshot_list(BlockDriverState *bs, QEMUSnapshotInfo **psn_tab)
>          }
>  
>          /* we don't need to read entire object */
> -        ret = read_object(fd, s->bs, (char *)&inode,
> +        ret = read_object(fd, s->bs, (char *)inode,
>                            vid_to_vdi_oid(vid),
>                            0, SD_INODE_HEADER_SIZE, 0,
>                            s->cache_flags);
> @@ -2998,17 +2999,17 @@ static int sd_snapshot_list(BlockDriverState *bs, QEMUSnapshotInfo **psn_tab)
>              continue;
>          }
>  
> -        if (!strcmp(inode.name, s->name) && is_snapshot(&inode)) {
> -            sn_tab[found].date_sec = inode.snap_ctime >> 32;
> -            sn_tab[found].date_nsec = inode.snap_ctime & 0xffffffff;
> -            sn_tab[found].vm_state_size = inode.vm_state_size;
> -            sn_tab[found].vm_clock_nsec = inode.vm_clock_nsec;
> +        if (!strcmp(inode->name, s->name) && is_snapshot(inode)) {
> +            sn_tab[found].date_sec = inode->snap_ctime >> 32;
> +            sn_tab[found].date_nsec = inode->snap_ctime & 0xffffffff;
> +            sn_tab[found].vm_state_size = inode->vm_state_size;
> +            sn_tab[found].vm_clock_nsec = inode->vm_clock_nsec;
>  
>              snprintf(sn_tab[found].id_str, sizeof(sn_tab[found].id_str),
> -                     "%" PRIu32, inode.snap_id);
> +                     "%" PRIu32, inode->snap_id);
>              pstrcpy(sn_tab[found].name,
> -                    MIN(sizeof(sn_tab[found].name), sizeof(inode.tag)),
> -                    inode.tag);
> +                    MIN(sizeof(sn_tab[found].name), sizeof(inode->tag)),
> +                    inode->tag);
>              found++;
>          }
>      }
>