Frankly I'm amazed. Above you wrote up the one reason why anyone would do such a factor as cleaning the cache on Linux: testing - particularly benchmarking. Then you go ahead and clarify how you can arrange a cron job that cleans the cache every night. Any newbie studying this may think that cleansing the cache (and even reconnecting the swap partition) is a good thing to do for administration purposes, like you'd do once you clear the disk cache for Web Explorer on a Home windows machine. It isn’t. The reason why it is not is in your article, however the way how it is talked about embedded in instructions on the best way to do it anyway seems to be deceptive to newbies so please permit me to clarify. Yes, there are some purposes around that hog memory so unhealthy that the system memory could also be eaten up and the system starts migrating memory pages onto the swap partition. Firefox comes to thoughts as it could actually develop into an issue when operating with only 2GB of system memory.

Even should you close tabs of particularly memory hungry web pages (ebay is a extremely unhealthy offender right here) not all of the code in Memory Wave shall be released as it should be. Keep in thoughts here that that is an issue of the appliance and not Linux though. This means you won’t get that memory again by fiddling with the os, like dropping the cache anyway. The intervention required would be to do something about Firefox. The only means I know of to get the memory back is to terminate the offending process i.e. Firefox. A notable exception to this are databases that can appear to hog memory if they aren't correctly configured (opposed to poor memory management inside the application) however even then you’ll need to look at your database first (whereas keeping in mind that ‘Database Administrator’ is a job description for a purpose. Whatever you do, purging the cache won’t help).

So yes, what I am saying is that the preposition within the second sentence of this article is false. When you've got a course of that's consuming up your memory then purging the cache won’t even contact it, whereas the process is running. Terminating the process will launch the memory. Generally you may even observe how the kernel decides to discard many of the memory claimed by such a terminated process itself, i.e. it doesn’t even keep it in the cache. If the process claimed sufficient memory, it may have displaced a variety of important code from the memory into the swap area causing the pc to run slower for boost brain function a short time longer until that memory code is retrieved. For those who don’t like tea you could simply want to proceed what you've been doing without reconnecting your swap as it in all probability won’t take lengthy for the memory to migrate back anyway. NOT reconnecting swap could have the benefit that solely the code that is actually wanted might be positioned again into memory (my most popular choice).

So: reconnecting swap will eat extra system resources overall than letting the kernel deal with it. Don't reconnect swap on a dwell production system until you really suppose you realize what you might be doing. But then I shouldn’t should say this as you'd discover out about this anyway whereas doing all your research / testing as you should when doing this type of stuff on a dwell manufacturing system. Here is one other thought. Possibly the cache-drop fallacy comes from the way in which memory usage is traditionally accounted for on Linux systems. Par instance if you happen to open ‘top‘ in a terminal and look at the row the place it says ‘Mem‘, Memory Wave there are entries ‘free‘ and ‘used‘ memory. Now the stats for used memory always contains the memory used for caching and buffering. The free memory is the memory that's not used at all. So if you want to know the memory used for os and functions subtract buffer and cache values from the used memory and boost brain function you’ll get the footprint of all the residual memory used for applications.

If you happen to don’t know that and only checked out the quantity of free memory you'll have thought you had been truly operating out of physical memory, but as long as there may be loads of memory used by the cache this is not true. When you drop the cache as described above, high will report all that memory as free memory but this is actually not what you thought you wanted - unless you might be testing or benchmarking (see Ole Tanges put up here for an instance). Now the coverage of the Linux kernel is to make use of as much of the memory as it could for one thing useful. First precedence obviously goes to os / utility code. It’s written above within the article but I’ll say it right here once more: the information within the cache are copies of files saved in your important drive. It’s stored there just in case it’s needed once more, so it’s there lots faster than having to learn it from the drive once more.

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