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voyage_on_alix [2012/03/10 21:08]
scytheman [Mode Switch Button] moved copyright note
voyage_on_alix [2014/03/01 17:13] (aktuell)
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 Note 1: By combining write cycles and reducing their interval you increase the risk of loosing data on crashes or power failure (here: up to 10min of work). Additionally,​ memory usage increases. Note 1: By combining write cycles and reducing their interval you increase the risk of loosing data on crashes or power failure (here: up to 10min of work). Additionally,​ memory usage increases.
  
-Note 2: You can monitor application'​s write operations by executing ''​echo 1 > /​proc/​sys/​vm/​block_dump''​ and watching the output of ''​dmesg''​ or ''/​var/​log/​syslog''​.+Note 2: You can monitor application'​s ​read and write operations by executing ''​echo 1 > /​proc/​sys/​vm/​block_dump''​ and watching the output of ''​dmesg''​ or ''/​var/​log/​syslog''​. ''​echo 0 > /​proc/​sys/​vm/​block_dump''​ disables the logging again.
  
 Note 3: Activating the kernel'​s laptop mode by setting ///​proc/​sys/​vm/​laptop_mode//​ to a value >0 should have no effect for flash drives as they don't need to be spun down. As the kernel documentation says: "When the knob is set, any physical disk I/O (that might have caused the hard disk to spin up) causes Linux to flush all dirty blocks. The result of this is that after a disk has spun down, it will not be spun up anymore to write dirty blocks, because those blocks had already been written immediately after the most recent read operation."​ Note 3: Activating the kernel'​s laptop mode by setting ///​proc/​sys/​vm/​laptop_mode//​ to a value >0 should have no effect for flash drives as they don't need to be spun down. As the kernel documentation says: "When the knob is set, any physical disk I/O (that might have caused the hard disk to spin up) causes Linux to flush all dirty blocks. The result of this is that after a disk has spun down, it will not be spun up anymore to write dirty blocks, because those blocks had already been written immediately after the most recent read operation."​
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 ==== Mode Switch Button ==== ==== Mode Switch Button ====
  
-The ALIX board has a nice mode switch button ​which state can be checked via a GPIO port. I wrote a tiny program to execute a configurable command ​when the button is pressed ​(default ​action: shutdown). Just save it as //​alix_gpio.cpp//,​ compile it by executing ''​g++ -o alix_gpio alix_gpio.cpp''​ and run //​alix_gpio//​ at system startup (it will automatically put itself into the background).+The ALIX board has a nice mode switch button ​whose state can be checked via a GPIO port. I wrote a tiny program to execute a configurable command (default: shutdown) ​when the button is pressed and to toggle some LEDs. Just save it as //​alix_gpio.cpp//,​ compile it by executing ''​g++ -o alix_gpio alix_gpio.cpp''​ and run //​alix_gpio//​ at system startup (it will automatically put itself into the background).
  
 <code cpp> <code cpp>
voyage_on_alix.1331410134.txt.gz · Zuletzt geändert: 2014/03/01 17:13 (Externe Bearbeitung)