PostgreSQL version:

backend_flush_after

Whenever more than backend_flush_after bytes have been written by a single backend, attempt to force the OS to issue these writes to the underlying storage. Doing so will limit the amount of dirty data in the kernel's page cache, reducing the likelihood of stalls when an fsync is issued at the end of a checkpoint, or when the OS writes data back in larger batches in the background. Often that will result in greatly reduced transaction latency, but there also are some cases, especially with workloads that are bigger than shared_buffers, but smaller than the OS's page cache, where performance might degrade. This setting may have no effect on some platforms. The valid range is between 0, which disables forced writeback, and 2MB. The default is 0, i.e., no forced writeback. (If BLCKSZ is not 8kB, the maximum value scales proportionally to it.)

Recommendations

Unless you have time to tune memory flushing behavior and test for improvements/regressions
Type: integer
Default: 0
Min: 0
Max: 256
Unit: 8kB
Context: user
Restart: false
Since: 9.6

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