אירועים והרצאות בפקולטה למדעי המחשב ע"ש הנרי ומרילין טאוב
יום חמישי, 16.01.2014, 12:30
The number of guest virtual machines that can be consolidated on one
physical host is typically limited by the memory size, motivating
memory overcommitment. Guests are given a choice to either install a
“balloon" driver to coordinate the overcommitment activity, or to
experience degraded performance due to uncooperative swapping.
Ballooning, however, is not a complete solution, as hosts must still
fall back on uncooperative swapping in various circumstances.
Additionally, ballooning takes time to accommodate change, and so
guests might experience degraded performance under changing
Our goal is to improve the performance of hosts when they fall back on
uncooperative swapping and/or operate under changing load conditions.
We carefully isolate and characterize the causes for the associated
poor performance, which include various types of superfluous swap
operations, decayed swap file sequentiality, and ineffective prefetch
decisions upon page faults. We address these problems by implementing
VSwapper, a guest-agnostic memory swapper for virtual
environments that allows efficient, uncooperative overcommitment. With
inactive ballooning, VSwapper yields up to an order of magnitude
performance improvement. Combined with ballooning, VSwapper can achieve
up to double the performance under changing load conditions.