[LU-5391] osd-zfs: ZAP objects use 4K blocks for both indirect and leaf blocks

• Type: Bug
• Resolution: Fixed
• Priority: Major
• Fix Version/s: Lustre 2.7.0
• Affects Version/s: Lustre 2.7.0
• Labels: prz zfs
• Severity: 3
• Assignee: Isaac Huang (Inactive)
• Reporter: Isaac Huang (Inactive)

Description

For example, on a MDS an oi.xx directory:
Object lvl iblk dblk dsize lsize %full type
44 4 4K 4K 1.06M 4.04M 99.71 ZFS directory

The code in __osd_zap_create():
oid = zap_create_flags(uos->os, 0, flags | ZAP_FLAG_HASH64, DMU_OT_DIRECTORY_CONTENTS, 12, 12, DMU_OT_SA, DN_MAX_BONUSLEN, tx);

This seemed inefficient. In fact the default leaf block size for fat ZAP is 16K:
int fzap_default_block_shift = 14; /* 16k blocksize */

I changed the block sizes to 16K indirect and 128K leaf, and saw a 10% increase in mds-survey creation rates.