[LU-14894] Parallel pass2 support for e2fsck

• Type: Improvement
• Resolution: Unresolved
• Priority: Major
• Labels: e2fsck ldiskfs
• Assignee: WC Triage
• Reporter: Wang Shilong (Inactive)

Description

LU-8465 implemented parallel inode table scanning for e2fsck pass1, and parallel bitmap loading for e2fsck pass5.

After these improvements, e2fsck of a 50% full 1PB filesystem running with 256 threads improved pass1 from 7777s to 191s (40x faster), and pass5 from 10523s to 286s (36x faster).

However, pass2 only improved marginally, from 1363s to 1265s (7%) and this now dominates the total e2fsck runtime (70% in this test) on large OSTs, and limits the aggregate speedup of e2fsck to "only" 10x faster despite the other improvements.

Processing directories in parallel should also be possible, in order to further speed up e2fsck times on large OSTs, and expecially on large MDT filesystems.

Issue Links

• is duplicated by: LU-14679 parallel e2fsck for pass2 directory scanning
• is related to: LU-16170 parallel e2fsck summary inode count is incorrect
• is related to: LU-16169 parallel e2fsck pass1 balanced group distribution
• is related to: LU-14168 e2fsck should avoid moving files into lost+found
• is related to: LU-14213 enable parallel e2fsck by default
• is related to: LU-8465 parallel e2fsck performance at scale