Just annotations of little "how to's", so I know I can find how to do something I've already done when I need to do it again, in case I don't remember anymore, which is not unlikely. Hopefully they can be useful to others, but I can't guarantee that it will work, or that it won't even make things worse.
Interesting "ask ubuntu" message related to swappiness tweaks
Posted 07-09-2014 at 09:06 PM by the dsc
Why most people recommend to reduce swappiness to 10-20?
Because most believe that swapping = bad and that if you don't reduce swappiness, the system will swap when it really doesn't need to. Neither of those are really true. People associate swapping with times where their system is getting bogged down - however, it's mostly swapping because the system is getting bogged down, not the other way around. It's true that there are certain times when swapping can have a noticeable performance penalty, but the system will have already factored that in to its decision to swap, and decided that not doing so would have a greater overall penalty in system performance or stability which may later become noticeable. Overall the default settings should result in the best overall performance and reliability. I'd recommend leaving it at the default.
But how can swap speed up my system? Doesn't swapping slow things down?
The act of transferring data from RAM to swap is a slow operation, but it's only taken when the kernel is pretty sure the overall benefit will outweigh this. For example, if your application memory has risen to the point that you have almost no cache left and your I/O is very inefficient because of this, you can actually get a lot more speed out of your system by freeing up some memory, even after the initial expense of swapping data in order to free it up.
The full message is considerably lengthier.