9

when I run the atop -r /var/log/atop/...

I see from the atop screen this

 PAG | scan  641376 |  steal 635209 | stall

the PAG is colored with red

can someone explain what PAG explain from the atop , and what this problem means ?

yael
  • 1,511
  • 11
  • 33
  • 57

1 Answers1

10

man atop

PAG Paging frequency. This line contains the number of scanned pages ('scan') due to the fact that free memory drops below a particular threshold and the number times that the kernel tries to reclaim pages due to an urgent need (`stall').

Also the number of memory pages the system read from swap space ('swin') > and the number of memory pages the system wrote to swap space ('swout') > are shown.

Basically, it (normally) indicates that your system is low on memory, which is not a good thing, hence it is in red.

zeppelin
  • 3,782
  • 10
  • 21
  • so your suggestion is to increase the memory ?, and how to configure the memory pages ? according to what ? – yael Nov 01 '16 at 10:53
  • > so your suggestion is to increase the memory ? Well, probably, your original question was on what PAG is, so I've provided you with a description of it. – zeppelin Nov 01 '16 at 11:04
  • > and how to configure the memory pages ? according to what ? You will normally just configure the total memory (and swap) limits, as pages are low level kernel thing, not something you have to reconfigure during the normal operation. – zeppelin Nov 01 '16 at 11:08
  • The first thing to check is an overall memory usage for your system, with the "free" command. – zeppelin Nov 01 '16 at 11:09
  • 1
    What does "steal" relate to? The atop man-page describes (cycle?) stealing in the context of virtual machines, but that does not seem to be what is shown under PAG. – Timo Reimann Nov 08 '19 at 15:46
  • 1
    @TimoReimann according to `sar(1)` Number of pages the system has reclaimed from cache (pagecache and swapcache) per second to satisfy its memory demands. – azat Jan 21 '20 at 09:49