[LU-7235] ZFS: dmu_object_alloc() serializes object creations

• Type: Improvement
• Resolution: Fixed
• Priority: Minor
• Labels: zfs
• Assignee: Alex Zhuravlev
• Reporter: Alex Zhuravlev

Description

dmu_object_alloc() in ZFS serializes object creations with a mutex:

dmu_object_alloc(objset_t *os, dmu_object_type_t ot,
                  int dmu_object_type_t bonustype,
                  int bonuslen, dmu_tx_t *tx)
{
	uint64_t object;
	uint64_t L2_dnode_count = DNODES_PER_BLOCK <<
	    (DMU_META_DNODE(os)->dn_indblkshift - SPA_BLKPTRSHIFT);
	dnode_t *dn = NULL;
	int restarted = B_FALSE;

	mutex_enter(&os->os_obj_lock);

this can be a bottleneck holding metadata performance much lower compared to ldiskfs where inode creation is more concurrent.

Issue Links

• is blocking: LU-2600 lustre metadata performance is very slow on zfs