Reduce the queue depth of loop devices used by the zram driver
Make the queue depth of loop devices identical to that of the underlying
storage device. This patch reduces latency by lowering the queue depth.
With this patch applied I see the following:
# cat /sys/block/loop30/queue/nr_requests
32
Bug: 194450129
Test: Built Android images, installed these and verified that the queue depth of loop devices is 32 instead of 256.
Change-Id: Ifa16084c7df3a54d9559c2388abc4a8392ff88c6
Signed-off-by: Bart Van Assche <bvanassche@google.com>
diff --git a/fs_mgr/blockdev.h b/fs_mgr/blockdev.h
new file mode 100644
index 0000000..2c0d68a
--- /dev/null
+++ b/fs_mgr/blockdev.h
@@ -0,0 +1,21 @@
+/*
+ * Copyright (C) 2021 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <android-base/result.h>
+#include <string>
+
+android::base::Result<void> ConfigureQueueDepth(const std::string& loop_device_path,
+ const std::string& file_path);