I have a system with 64gb of ram that I'm running smartos on. It has 5
Windows Server 2012 KVM VMs each with 8GB of memory. There is also a
smartos zone with 32GB max_physical_memory that runs a very lightweight
file server that i wrote in Go. The file server typically consumes about
3-4GB of memory. Every so often (like once in 10 minutes or so) the
fileserver massively slows down. I noticed that normally the RSS entry for
the fileserver in the output of prstat stays stable. However, these periods
of slowdown perfectly coincide with the RSS values decreasing. This led me
to conclude that memory allocated to the fileserver is being paged out.
Furthermore the fraction of misses as shown in the output of arcstat also
masively increases during these periods. Therefore, my tentative conclusion
is that memory is being paged out from the fileserver and being given to
the ARC.

This is the output of memstat

Kernel                    3612239             14110   22%
ZFS File Data             1474454              5759    9%
Anon                     11110378             43399   66%
Exec and libs                2429                 9    0%
Page cache                  14309                55    0%
Free (cachelist)            11307                44    0%
Free (freelist)            535660              2092    3%

Any suggestions on how I can confirm that this is indeed what's going on
and how I can fix it? One solution that would work for me would be to
dedicate say 4-6GB of RAM to the fileserver zone but I can't seem to find
an option in vmadm to do that.

Thanks,
Rajesh



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