# Linux 7.4 workqueue flush optimization yields 10-100x speedup on large servers

> **Key takeaway:** A workqueue optimization by Tejun Heo in Linux 7.4 makes idle flushes 10 to 100 times faster on large CPU-count systems by only visiting queues used since the last flush.

**Published:** 2026-10-23T00:38:20+00:00 
**Source:** Phoronix Benchmarks & Drivers 
**Category:** kernel-os 
**Canonical URL:** https://fosswire.org/news/linux-74-workqueue-flush-optimization-yields-10-100x-speedup.html 

## Summary
Linux 7.4 includes a workqueue optimization that dramatically reduces flush overhead on high core-count servers. The change, authored by longtime developer Tejun Heo, targets a bottleneck reported by Huawei engineer Yao Kai where XFS log force operations spent up to 64 microseconds per flush on a 128-CPU machine. By tracking which queues have been used since the last flush rather than scanning all possible CPUs, the kernel avoids unnecessary workqueue walks.

## Benchmark numbers from the commit
- **Idle per-cpu workqueue**: 40K → 4.2M flushes/second on a 192-CPU 2-node machine
- **Idle unbound workqueue**: 450K → 4.3M flushes/second on same hardware
- **16-thread contended load**: per-cpu 30K → 110K flushes/sec; unbound 60K → 180K flushes/sec
- **Dense flushes with all pwqs active**: unchanged for per-cpu, 15-20% slower for unbound
- **Queue submission path**: no change in latency
- **Original pain point**: XFS CIL workqueue flushed on every log force, up to 64µs per flush on 128-CPU system

## Why it matters
The improvement directly benefits large-scale server workloads using XFS and other subsystems that frequently flush workqueues. Enterprise Linux deployments on high core-count Intel Xeon and AMD EPYC hardware should see reduced latency in I/O-bound operations.