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repo: Optimize memory use of ostree_repo_list_objects()

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I was looking at https://github.com/ostreedev/ostree/pull/2632
and confused at the usage of
`GVariant *value = g_variant_new ("(b@as)", TRUE, g_variant_new_strv (NULL, 0));`
which looked strange - why the empty strv?

It turns out that this is a historical legacy of the time when
ostree had pack files.  And nothing actually cares about the values
of these variants; we should have an API that returns a proper set,
and not a hash.

But...since all of these things have exactly the same value, instead
of allocating lots of redundant copies on the heap, just have
them all hold a refcount on a shared value.

This cuts the heap usage from 20MB to 13MB on a test FCOS repository
build.
This commit is contained in:
Colin Walters 2022-06-07 20:30:09 -04:00
parent 2b6f506f70
commit c2baa6d10b
1 changed files with 9 additions and 5 deletions
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14
src/libostree/ostree-repo.c
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@ -3895,6 +3895,7 @@ ostree_repo_get_parent (OstreeRepo *self)
static gboolean
list_loose_objects_at (OstreeRepo *self,
GVariant *dummy_value,
GHashTable *inout_objects,
int dfd,
const char *prefix,
@ -3902,7 +3903,7 @@ list_loose_objects_at (OstreeRepo *self,
GCancellable *cancellable,
GError **error)
{
GVariant *key, *value;
GVariant *key;
g_auto(GLnxDirFdIterator) dfd_iter = { 0, };
gboolean exists;
@ -3971,11 +3972,10 @@ list_loose_objects_at (OstreeRepo *self,
}
key = ostree_object_name_serialize (buf, objtype);
value = g_variant_new ("(b@as)",
TRUE, g_variant_new_strv (NULL, 0));
/* transfer ownership */
g_hash_table_replace (inout_objects, g_variant_ref_sink (key),
g_variant_ref_sink (value));
g_variant_ref (dummy_value));
}
return TRUE;
@ -3989,6 +3989,9 @@ list_loose_objects (OstreeRepo *self,
GError **error)
{
static const gchar hexchars[] = "0123456789abcdef";
// For unfortunate historical reasons we emit this dummy value.
g_autoptr(GVariant) dummy_loose_object_variant =
g_variant_ref_sink (g_variant_new ("(b@as)", TRUE, g_variant_new_strv (NULL, 0)));
for (guint c = 0; c < 256; c++)
{
@ -3996,7 +3999,8 @@ list_loose_objects (OstreeRepo *self,
buf[0] = hexchars[c >> 4];
buf[1] = hexchars[c & 0xF];
buf[2] = '\0';
if (!list_loose_objects_at (self, inout_objects, self->objects_dir_fd, buf,
if (!list_loose_objects_at (self, dummy_loose_object_variant,
inout_objects, self->objects_dir_fd, buf,
commit_starting_with,
cancellable, error))
return FALSE;