[Qemu-devel] [PATCH v2 0/2] sheepdog: remove huge BSS object

[Qemu-devel] [PATCH v2 0/2] sheepdog: remove huge BSS object

[Paolo Bonzini]

block/sheepdog.o has a 4M static variable that is 90% of QEMU's whole .bss
section.  Since it doesn't really have to be static, we can just use a
heap allocated block.  We can actually make it smaller too. :)

Patch 1 is a related cleanup since we're touching that area of the code.

Paolo

v1->v2: free the data...

Paolo Bonzini (2):
  sheepdog: cleanup repeated expression
  sheepdog: remove huge BSS object

 block/sheepdog.c | 27 ++++++++++++++-------------
 1 file changed, 14 insertions(+), 13 deletions(-)

-- 
2.17.0

[Qemu-devel] [PATCH 1/2] sheepdog: cleanup repeated expression

[Paolo Bonzini]

The expression "SD_INODE_SIZE - sizeof(inode.data_vdi_id)" already has a macro
defined for the same value (though with a nicer definition using offsetof).
Replace it.

Reviewed-by: Fam Zheng <famz@redhat.com>
Reviewed-by: Jeff Cody <jcody@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 block/sheepdog.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/block/sheepdog.c b/block/sheepdog.c
index 4237132419..23cf5a8430 100644
--- a/block/sheepdog.c
+++ b/block/sheepdog.c
@@ -2337,7 +2337,7 @@ static int sd_truncate(BlockDriverState *bs, int64_t offset,
     }
 
     /* we don't need to update entire object */
-    datalen = SD_INODE_SIZE - sizeof(s->inode.data_vdi_id);
+    datalen = SD_INODE_HEADER_SIZE;
     s->inode.vdi_size = offset;
     ret = write_object(fd, s->bs, (char *)&s->inode,
                        vid_to_vdi_oid(s->inode.vdi_id), s->inode.nr_copies,
@@ -2705,7 +2705,7 @@ static int sd_snapshot_create(BlockDriverState *bs, QEMUSnapshotInfo *sn_info)
      */
     strncpy(s->inode.tag, sn_info->name, sizeof(s->inode.tag));
     /* we don't need to update entire object */
-    datalen = SD_INODE_SIZE - sizeof(s->inode.data_vdi_id);
+    datalen = SD_INODE_HEADER_SIZE;
     inode = g_malloc(datalen);
 
     /* refresh inode. */
@@ -2991,7 +2991,7 @@ 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,
                           vid_to_vdi_oid(vid),
-                          0, SD_INODE_SIZE - sizeof(inode.data_vdi_id), 0,
+                          0, SD_INODE_HEADER_SIZE, 0,
                           s->cache_flags);
 
         if (ret) {
-- 
2.17.0

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

[Paolo Bonzini]

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.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 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++;
         }
     }
@@ -3019,6 +3019,7 @@ out:
     *psn_tab = sn_tab;
 
     g_free(vdi_inuse);
+    g_free(inode);
 
     if (ret < 0) {
         return ret;
-- 
2.17.0

Re: [Qemu-devel] [PATCH v2 0/2] sheepdog: remove huge BSS object

[Jeff Cody]

On Wed, May 23, 2018 at 06:07:19PM +0200, Paolo Bonzini wrote:
> block/sheepdog.o has a 4M static variable that is 90% of QEMU's whole .bss
> section.  Since it doesn't really have to be static, we can just use a
> heap allocated block.  We can actually make it smaller too. :)
> 
> Patch 1 is a related cleanup since we're touching that area of the code.
> 
> Paolo
> 
> v1->v2: free the data...
> 
> Paolo Bonzini (2):
>   sheepdog: cleanup repeated expression
>   sheepdog: remove huge BSS object
> 
>  block/sheepdog.c | 27 ++++++++++++++-------------
>  1 file changed, 14 insertions(+), 13 deletions(-)
> 
> -- 
> 2.17.0
> 

Thanks,

Applied to my block branch:

git://github.com/codyprime/qemu-kvm-jtc block

-Jeff