On 06.06.2015 04:48, Dennis Jacobfeuerborn wrote: > On 05.06.2015 19:47, Greg Lindahl wrote: >> On Fri, Jun 05, 2015 at 09:33:11AM -0700, Gordon Messmer wrote: >>> On 06/05/2015 03:29 AM, Markus "Shorty" Uckelmann wrote: >>>> some (probably unused) parts are swapped out. But, some of >>>> those parts are the salt-minion, php-fpm or mysqld. All services which >>>> are important for us and which suffer badly from being swapped out. >>> >>> Those two things can't really both be true. If the pages swapped >>> out are unused, then the application won't suffer as a result. >> >> No. >> >> Let's say the application only uses the page once per hour. If there >> is also I/O going on, then it's easy to see that the kernel could >> decide to page the page out after 50 minutes, leaving the application >> having to page it back in 10 minutes later. > > That's true but it also means that if you lock that page so it cannot be > swapped out then this page is not available for the page cache so you > incur the i/o hit either way and it's probably going to be worse because > the system has no longer an option to optimize the memory management. > I wouldn't worry about it until there's actually permanent swap activity > going on and then you have to decide if you want to add more ram to the > system or maybe find a way to tell e.g. Bacula to use direct i/o and not > pollute the page cache. > For application that do not allow to specify this a wrapper could be > used such as this one: > http://arighi.blogspot.de/2007/04/how-to-bypass-buffer-cache-in-linux.html Actually I found better links: https://code.google.com/p/pagecache-mangagement/ http://lwn.net/Articles/224653/ "It is to address the "waah, backups fill my memory with pagecache" and the "waah, updatedb swapped everything out" and the "waah, copying a DVD gobbled all my memory" problems." Regards, Dennis