I do not know where the various rules-of-thumb came from, but suspect it mostly was from production multiuser/multiprocess systems where the emphasis was on throughput, I/O wait was common, and it throughput could be increased by overcommitting real memory and thereby reducing the processor idle time that occurs because processes are waiting for I/O completion. The target model would be a zSeries mainframe or large Unix or Windows server with many jobs running.
On a desktop system, probably with one and a small fraction users, not all that many background processes, and, with present memory prices being what they are, enough memory to hold them all, the swap requirement is lower, and possibly zero. In general, you do not really want to swap, ever, especially on an interactive system. Swapping (now usually paging, which is somewhat different) always will degrade performance, and should be avoided if possible. That said, another poster noted that if hibernation is an option, swap is where the memory image is put, and it should be at least as large as real memory. You can estimate the need for operational swap reasonably using utilities like top and vmstat. Top will show maximum swap for the current boot at a glance; if it is zero, no swap has been used since the last boot, and if the system has been up for a while that indicates a zero (or at least small) swap requirement. If the amount is not zero, it would be reasonable to add half a GB or so to the peak swap and round up to next full GB. Bad things are likely if you run out of (memory + swap). If it is a laptop and you want to use hibernate, set swap to the larger of the operational swap size and the system memory size. Tom Dial On 02/04/2016 08:42 AM, Jos Collin wrote: > Hello, > > How much swap space does 4GB ram ideally requires ? I have been using > the rule "RAM size x 2" for calculating the size of swap. But as the RAM > sizes are bigger nowadays, is this a wrong calculation ? I mean, is it > okay if I use 1 GB of swap space (or lesser) for a 4gb RAM ? > > (I use to suspend my system everyday by pressing alt+shutdown menu in > gnome 3) > > Please suggest. > > Thanks, > Jos Collin >
