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 configured the guest for), but our customers (or in particular, their VM guys) would really like vmware tools or open-vm-tools by default. From what we gather, many sites choose to "over provision" the memory in the VM setups, and when memory gets low, the host takes back 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. -- Paul Koch | Founder, CEO AKIPS Network Monitor http://www.akips.com Brisbane, Australia
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