Severe paging problem in Solaris 2.4

Severe paging problem in Solaris 2.4

Post by Michael Bry » Sat, 12 Aug 1995 04:00:00



We are experiencing extremely high paging rates on our Solaris 2.4 system.
It is a Sparc5 with 32MB of RAM.  It is connected to an Ethernet network
with minimal traffic.  With two users on the system (one using OpenWindows
on the console, one connected via telnet), the system performance goes out
the window:

  1) Telnet user is running 'make', which uses 'gcc' to compile
     code --- full compilation in about 20 directories takes
     under 5 minutes.

  2) OpenWindows user just has a shell window open.  His response
     time is horrendous, with delays of several seconds.

Running "vmstat 1" shows extremely high paging rates, with "pi" and "po"
both averaging somewhere over 800.  If the OpenWindows user logs off,
these paging rates go down close to 0, even during the 'make'.

Similarly, with six progams in the background, all of them idle, but all
with 500K of private shared memory mapped in, paging rates during the
'make' are very high.  If the six programs are terminated, the paging
level goes back down.  The shared memory is not marked as "locked", so
this really doesn't make sense.

Similar tests on a SunOS 4.1.3 system with the same hardware do not
exhibit this heavy paging behaviour.

As I said, there is 32MB of RAM on the system.  During these tests, it
appears that about 20MB of swap space is reserved (there is over 100MB
of swap space on the system).  Theoretically, the paging could be stopped
by going up to 64MB of RAM, but the activities on this system should be
able to work properly in just 32MB of RAM, and that in fact seems to
be the case on the 4.1.3 system.

Does anybody know of any problems with 2.4 that might be causing this?
Are there any parameters I can examine or tune to help determine the
cause of the heavy paging?  I know that HP-UX 9.x systems had a problem
with dynamic buffer cacheing, which exhibited similar symptoms, but I have
not yet found a way to determine how much memory is being used by
Solaris's buffer cache, and I don't know if something similar is happening
here.

If possible, e-mail any responses in addition to posting --- our news
feed has been a bit flaky the last few days.

Thanks!

 
 
 

Severe paging problem in Solaris 2.4

Post by Gavin Malt » Thu, 17 Aug 1995 04:00:00


: Running "vmstat 1" shows extremely high paging rates, with "pi" and "po"
: both averaging somewhere over 800.  If the OpenWindows user logs off,
: these paging rates go down close to 0, even during the 'make'.

Hi

Look at the sr "scan rate" column in vmstat output.  If it
sits above a couple of hundred pages then you have a high
memory paging rate.  The pi and po columns also reflect
disk I/O which is also implemented through the paging
system, so they do get very high.

I'd get a tool like proctool and start to see which are
the hogs.

Cheers

Gavin

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