EXT4 Fast Commit Mode To Be Even Faster With Linux 5.18

Added back in 2020 with the Linux 5.10 kernel was the new EXT4 "fast commits" mode for reducing commit latency in the ordered data mode. Now for the upcoming Linux 5.18 cycle, that fast commits mode should be even faster.

Queued into the EXT4 "dev" Git branch ahead of the Linux 5.18 merge window opening later this month are improvements to the fast_commit performance and scalability.

IBM engineer Ritesh Harjani took up further optimizing EXT4's fast commit mode. Ritesh explained with the pending patch, "Currently ext4_fc_commit_dentry_updates() is of quadratic time complexity, which is causing performance bottlenecks with high threads/file/dir count with fs_mark. This patch makes commit dentry updates (and hence ext4_fc_commit()) path to linear time complexity. Hence improves the performance of workloads which does fsync on multiple threads/open files one-by-one."

The results are looking very good now for the performance and scalability of EXT4's fast commits:

Look for this in Linux 5.18 if using the file-system's fast_commit mode.