bgwriter_delay
No restart — takes effect on reloadtime (ms)
How often the background writer wakes to flush dirty pages.
What it does
bgwriter_delay is the pause between background-writer rounds. Shorter delays make it flush more continuously (smoother I/O, more CPU wakeups); longer delays make it lazier.
How to tune it
The default 200 ms is fine for most. On bursty write workloads, shortening it (with a higher bgwriter_lru_maxpages) keeps more buffers clean so backends seldom stall writing a page themselves.