Update docs to highlight that the auditor chunk size can be set

May not be obvious, but existing code will let you change the
disk_chunk_size just for the auditor so this just points that
out in the docs.  In one short test I ran with a 4 node cluster
with 18GB of 4MB objects on it, changint he auditor chunk size
from the default of 64K to 1MB creased the auditor CPU time from
10% to 4%.

Also added test code to make sure this overridden value is
actually used and checked other auditWorker conf values as
well.

Change-Id: Ia12e1c6127877dc2124b60cd963cd0b6d5f3d6ef

doc/source/deployment_guide.rst

@@ -520,6 +520,7 @@ log_name            object-auditor  Label used when logging
 log_facility        LOG_LOCAL0      Syslog log facility
 log_level           INFO            Logging level
 log_time            3600            Frequency of status logs in seconds.
+disk_chunk_size     65536           Size of chunks read during auditing
 files_per_second    20              Maximum files audited per second per
                                     auditor process. Should be tuned according
                                     to individual system specs. 0 is unlimited.

etc/object-server.conf-sample

@@ -226,6 +226,9 @@ use = egg:swift#recon
 # log_level = INFO
 # log_address = /dev/log
 #
+# You can set the disk chunk size that the auditor uses making it larger if
+# you like for more efficient local auditing of larger objects
+# disk_chunk_size = 65536
 # files_per_second = 20
 # concurrency = 1
 # bytes_per_second = 10000000

test/unit/obj/test_auditor.py

@@ -78,6 +78,33 @@ class TestAuditor(unittest.TestCase):
         rmtree(os.path.dirname(self.testdir), ignore_errors=1)
         unit.xattr_data = {}
 
+    def test_worker_conf_parms(self):
+        def check_common_defaults():
+            self.assertEquals(auditor_worker.max_bytes_per_second, 10000000)
+            self.assertEquals(auditor_worker.log_time, 3600)
+
+        # test default values
+        conf = dict(
+            devices=self.devices,
+            mount_check='false',
+            object_size_stats='10,100,1024,10240')
+        auditor_worker = auditor.AuditorWorker(conf, self.logger,
+                                               self.rcache, self.devices)
+        check_common_defaults()
+        self.assertEquals(auditor_worker.diskfile_mgr.disk_chunk_size, 65536)
+        self.assertEquals(auditor_worker.max_files_per_second, 20)
+        self.assertEquals(auditor_worker.zero_byte_only_at_fps, 0)
+
+        # test specified audit value overrides
+        conf.update({'disk_chunk_size': 4096})
+        auditor_worker = auditor.AuditorWorker(conf, self.logger,
+                                               self.rcache, self.devices,
+                                               zero_byte_only_at_fps=50)
+        check_common_defaults()
+        self.assertEquals(auditor_worker.diskfile_mgr.disk_chunk_size, 4096)
+        self.assertEquals(auditor_worker.max_files_per_second, 50)
+        self.assertEquals(auditor_worker.zero_byte_only_at_fps, 50)
+
     def test_object_audit_extra_data(self):
         def run_tests(disk_file):
             auditor_worker = auditor.AuditorWorker(self.conf, self.logger,