Thanks to:
demeule_at_univ-lille3.fr
Knut.Hellebo_at_nho.hydro.com
alan_at_nabeth.cxo.dec.com
Programs:
swapon -s Displays swap space utilization
monitor
ftp://www.digital.com/pub/DEC/monitor.alpha.tar.Z
vmstat [-s] Displays virtual memory statistics
Other hints:
Read man pages for the programs mentioned above.
Paging across two disks allows the system to have multiple disks
seeking at the same time. If the disks are on separate disk
controllers, then the data transfers can also take place in parallel.
monitor is not tested.
Output from top explained:
> Memory: Real: 33M/110M act/tot Virtual: 155M/390M use/tot Free: 1040K
*1* *2* *3*
*1*: Top reports 110 M of memory because internal buffers e.g AdvFS
uses som memory and this is not available to the kernel.
*2*: Virtual: 121M/390M; There is 390 M of total memory swap on disk
and memory. 121 M of these are in use. Swapon -s will report this like
this:
Total swap allocation:
Allocated space: 50000 pages (390MB)
In-use space: 15497 pages ( 30%)
Available space: 34503 pages ( 69%)
*3*: 1040 KB of memory is free. But this could change as pages are
taken away from the buffer cache and given to a processes.
While this may not seem like much, Digital UNIX uses a unified buffer
cache (UBC). In older versions of UNIX, the file system buffer cache
used a fixed percentage of physical memory that was unavailable for
other uses. UBC systems allow all memory not locked down by the
kernel or real-time processes to be used equally for the buffer cache
and per-process memory needs. This tends to create lower overall
"free" memory numbers, but since most of the data in the buffer cache
was read, it is easy to reassign the memory to another process.
Kjell Andresen Systems administrator, University of Oslo, Norway
Center for Information Technology Services and
Department of Geophysics
Received on Tue Sep 24 1996 - 13:12:40 NZST