pgpgin|pgpgout|pswpin|pswpout意义与差异

引用来自: http://ssms.cs2c.com.cn/otrs/pc.pl?Action=PublicFAQZoom;ItemID=11741

文章主要意思是:

1. page in/out操作指把块设备中的页读入内存或把内存中的页写入块设备

When ever program or data needs to be accessed and is read in from its permanent location on disk, this is called a page in request.
When ever program or data needs to be saved and is written to a permanent location on disk, this is called a page out request.

2. page in/out中的页指disk sector,大小为512字节,而不是虚拟内存中的4k大小的页

The kernel tracks each disk page (512b) read in within the pgpgin (pages paged in) counter

3. pgpgin/pgpgout是指主存(内存)与块设备(硬盘)之间的page in/out的页数.

these counters are related to virtual memory "paging" only in the fact that they are doing disk io to load a memory page with data from disk or write the data from a memory page back to disk

4. pswpin/pswpout是指虚拟内存中,从块设备swap区中读入/读出的页数.因此是被包含在pgpgin/pgpgout中的.

pages swapped in or out are also counted within pages paged in or out respectively since swap io is still ultimately block device based.