mergerfs/mkdocs/docs/config/threads.md

threads

There are multiple thread pools used in mergerfs to provide parallel behaviors.

read-thread-count

Defaults to 0

The number of threads used to read messages from the kernel. If used alone processing will be done on the same thread. If process-thread-count is enabled then this thread pool will read messages and the process thread pool will do the work. This can increase how much mergerfs can process at one time but may reduce throughput.

• read-thread-count=0 and process-thread-count=-1: Create 1 read+process thread per logical CPU core upto 8.
• read-thread-count=N where N>0 and process-thread-count=-1: Create a thread pool of N read+process threads.
• read-thread-count=N where N<0 and process-thread-count=-1: Create a read+process thread pool of CPUCount / -N threads. Minimum of 1.
• read-thread-count=0 and process-thread-count=0: Create 2 read threads and a process thread per logical CPU core upto 8.
• read-thread-count=0 and process-thread-count!=-1: Creates 2 read threads and number of process threads as defined below.

process-thread-count

Defaults to -1

When enabled this sets the number of threads in the message processing pool.

• process-thread-count=-1: Process thread pool is disabled.
• process-thread-count=0: Create 1 thread process thread per logical CPU core upto 8.
• process-thread-count=N where N>0: Create a thread pool of N threads.
• process-thread-count=N where N<-1: Create a thread pool of CPUCount / -N threads. Minimum of 1.

process-thread-queue-depth

Defaults to 2

Sets the depth queue for the processing thread queue per thread. Meaning if the read threads are getting requests faster than can be processed they will be queued up upto the queue depth. Despite the calculation being per thread the queue depth is shared across all in the pool.

• process-thread-queue-depth=N where N>0: Sets the number of outstanding requests that the process thread pool can have to N * process-thread-count. If requests come in faster than can be processed and the max queue depth hit then queuing the request will block in order to limit memory growth.
• process-thread-queue-depth<=0: Sets the queue depth to 2. May be used in the future to set dynamically.