| In SAP each process is using a big (300mb+) shared area. So the VSZ
shows all the processes as over 800M. Surely we dont allocate swap
space for the shared area, do we?
If I understand the eager allocation, at the time we start a process we
pre-allocate some swap space for its use. Of course, we dont know how
large the VSZ will get as that job maps shared memory, or as it
malloc's memory. So we must allocate some small ammount, and that must
grow as needed.
Is there anything I can read that gives a good explanation of the
alloction and management of swap space? Something outside the source
code, since I dont have access to source.
|
| >Surely we dont allocate swap
>space for the shared area, do we?
We do!, but only once.
>If I understand the eager allocation, at the time we start a process we
>pre-allocate some swap space for its use. Of course, we dont know how
>large the VSZ will get as that job maps shared memory, or as it
>malloc's memory. So we must allocate some small ammount, and that must
>grow as needed.
Under eager swap allocation mode, the swap space is "reserved" any time
virtual mmeory is allocated. There is no pre-allocation. Swap space
is "used" when a pageout occurs. Prior to V4.0, "reserve" implies "use"
as actual disk blocks are allocated.
You may find the cda tool useful in determining swap usage. You can get
a copy from the URL:
http://www.zk3.dec.com/~shashi/cda.html
The command to use is "kps -o", which will list the swap usage of all
processes.
--shashi
[Posted by WWW Notes gateway]
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