Difference between Swapping and Paging in linux

References: http://querieslinux.blogspot.com/2009/07/what-is-difference-between-swapping-and.html
Swapping occurs when whole process is transferred to disk,while paging is when some part of process is transferred to disk while rest is still in physical memory. There are two utilities to onitor memory, called vmstat (for bsd, etc),sar( for system V, etc). 
Page-ins and page-outs are pages moved in and out from physical memory to disk, swap-ins and swap-outs are processes moved in and out of disk.
The difference between swapping and paging is that paging swaps memory pages while swapping swaps the address space of complete processe

Paging:          

Only the required memory pages are moved to main memory from the swap device for execution. Process size does not matter.

After the CPU digests these, the next page is requested. If it is not found in RAM, a page fault occurs, signaling the kernel to load the next few pages from disk into RAM. This is called demand paging

Swapping:       

Whole process is moved from the swap device to the main memory for execution. Process size must be less than or equal to the available main memory

References: https://www.cs.duke.edu/csl/docs/sysadmin_course/sysadm-92.html

Swapping happens under a heavier work load. With swapping the kernel moves all segments belonging to a process to the swap area. The process is chosen if it's not expected to be run for a while. Before the process can run again it must be copied back into physical memory.

Disk area (swap space) is used as an extension of physical memory for temporary storage when the operating system tries to keep track of processes requiring more physical memory than what is available. When this happens the swap space is used for swapping and paging.
Paging is when individual memory segments, or pages, are moved to or from the swap area. When memory is low portions of a process (data areas, but not instructions which are available from local or remote file systems) are moved to free up memory space. Segments are chosen to be moved if they haven't been referenced recently. When the process next tries to reference this segment a page fault occurs and the process is suspended until the segment is returned to memory. A page fault is normally returned the first time a program is started, as it won't be in memory. It's then paged from the local or remote file system.

HowTo: Check Swap Usage in Linux
cat /proc/swaps
swapon -s
free -g
vmstat
# atop
# htop
# top
References: http://www.linux-tutorial.info/modules.php?name=MContent&obj=page&pageid=89
http://www.slideshare.net/sgpraju/os-swapping-paging-segmentation-and-virtual-memory
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