A value of swappiness=10
is recommended in Ubuntu's SwapFaq.
Why is a value of 10 is recommended rather than swappiness=0
?
Are there any pros of 10 or cons of zero?
swap
A value of swappiness=10
is recommended in Ubuntu's SwapFaq.
Why is a value of 10 is recommended rather than swappiness=0
?
Are there any pros of 10 or cons of zero?
Best Answer
swappiness=0
will wait to swap until it is absolutely necessary. Setting a moderate value likeswappiness=10
will cause pages to be swapped from memory to disk somewhat more readily. This can prevent the need to swap a lot at once; such a need can introduce annoying delays.In addition, often a process runs but does nothing for an extended time. Many daemons (background services) behave this way. You may have a background application that is left unused for a while. And these days some applications are implemented as multiple processes, like Chromium and Google Chrome, where each tab has a separate process behind it (not a separate thread, but a separate process). Setting
swappiness
to a value like 10 makes it so these background tasks that are not being actively used are swapped to memory even when they could remain crammed in RAM. Then when a more actively used process needs to allocate more RAM, it can do so more quickly.In conclusion, allowing processes to be swapped from RAM to disk earlier than necessary often confers a performance benefit and lower latencies when a process allocates memory. This is at the expense of the time it takes to swap the processes back. But this is usually done much less frequently than a process in active use allocates and releases memory, so the trade-off is often worthwhile.