Date: Tue, 26 Aug 2014 17:16:57 +1000 From: Paul Koch <paul.koch@akips.com> To: <freebsd-stable@freebsd.org> Subject: 10.0 interaction with vmware Message-ID: <20140826171657.0c79c54d@akips.com>
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Curious if anyone has an understanding of what actually goes on with VMWare memory control of a FreeBSD 10 guest when open-vm-tools is installed and how it could affect performance. Our typical customer environment is a largish VMWare server with an appropriate amount of RAM allocated to the guest, which currently runs FreeBSD 10.0p7 + our software, UFS root, and data stored on a ZFS partition. Our software mmaps large database files, does rather largish data collection (ping, snmp, netflow, syslog, etc) and mostly cruises along, but performance drops off a cliff in low memory situations. We don't install open-vm-tools at the moment, therefore we have a known amount of memory to work with (ie. what the customer initially=20 configured the guest for), but our customers (or in particular, their VM guys) would really like vmware tools or open-vm-tools by default. =46rom what we gather, many sites choose to "over provision" the memory in the VM setups, and when memory gets low, the host takes back=20 some of the RAM allocated to the guest. How does this work actually work ? Does it only take back what FreeBSD considers to be "free" memory or can the host start taking back "inactive", "wired", "zfs arc" memory ? We tend to rely on stuff being in inactive and zfs arc. If we start swapping, we are dead. Also, is there much of a performance hit if the host steals back free memory, and then gives it back ? We'd assume all memory the host gives to the guest is pre-bzero'ed so the FreeBSD wouldn't need to also bzero it. Paul. --=20 Paul Koch | Founder, CEO AKIPS Network Monitor http://www.akips.com Brisbane, Australia
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