Hi,
I just experimented a bit with the new cpuplugd from the
s390-tools-package (available in SLES10 SP2). I believe it could be a
nice way to dynamically adjust guest size in order to minimize Linux
file cache and there by z/VM paging. It looks very promising :-)
I tried out CMM1/VMRM earlier, but it kept reducing our guests until
they stopped answering and died. cpuplugd could be a fine way to let the
linux guests "adjust themselves".
I have a couple of questions for you:
1)
The man (5) page for cpuplugd mentions that the "acpr" variable is "The
amount of page cache reads (as listed in vmstat in the bi and bo
fields)". According to the man page for vmstat "bi" and "bo" is "Blocks
received from/sent to a block device (blocks/s)" - exactly what "page
cache" are they referring to?
2)
Am I the only one who thinks a "filecache" variable ("cached" from
/proc/meminfo) could be very useful? That is, considering Linux's
tendency to use all free memory for file cache - and all the problems it
creates in a virtual environment (related to LRU and slow single
threaded sequential z/VM paging).
3)
Can anyone explain the logic in the default HOTPLUG/HOTUNPLUG rules? -
Or the rationale of bringing "loadavg" to cpuplugd in the first place?
>From the man page:
hotplug = "(loadavg > onumcpus + 0.75) & (idle < 10.0)"
hotunplug = "(loadavg < onumcpus - 0.25) | (idle > 50)"
4)
Is it possible to monitor the number of pages a guest has assigned to
the "cmm1 page pool" at CP level? That is, the "dynamic guest size" seen
from CP point of view (not proc/sys/vm/cmm_pages) - For example from
Perfkit? (Unfortunately we don't have Velocity's performance products).
Kind regards
Klaus Johansen, Administrator
KMD Basic Infrastructure Services
Lautrupparken 40-42, DK-2750 Ballerup
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