Add in a tunable option for object server threads_per_disk and tune default to recommendations from http://docs.openstack.org/developer/swift/deployment_guide.html#object-server-configuration

config.yaml

@@ -55,3 +55,11 @@ options:
     description: |
       The CPU multiplier to use when configuring worker processes for the
       account, container and object server processes.
+  object-server-threads-per-disk:
+    default: 4
+    type: int
+    description: |
+      Size of the per-disk thread pool used for performing disk I/O. 0 means
+      to not use a per-disk thread pool. It is recommended to keep this value 
+      small, as large values can result in high read latencies due to large 
+      queue depths. A good starting point is 4 threads per disk.

hooks/swift_storage_context.py

@@ -69,5 +69,7 @@ class SwiftStorageServerContext(OSContextGenerator):
             'container_server_port': config('container-server-port'),
             'object_server_port': config('object-server-port'),
             'workers': psutil.NUM_CPUS * multiplier,
+            'object_server_threads_per_disk': config(
+                'object-server-threads-per-disk'),
         }
         return ctxt

templates/object-server.conf

@@ -12,6 +12,7 @@ recon_cache_path = /var/cache/swift
 
 [app:object-server]
 use = egg:swift#object
+threads_per_disk = {{ object_server_threads_per_disk }}
 
 [object-replicator]