Vmware, Inc.

Ishan Banerjee

Rajesh Venkatasubramanian

Kiran Tati

Preeti Agarwal

Xavier Deguillard

Julien Freche

Yury Baskakov

Jui-Hao Chiang

Qasim Ali

Carl Alan Waldspurger

Alexander T Garthwaite

Jesse Pool

Ashish Kaila

Nick Michael Ryan

Halesh Sadashiv

Mohammed Junaid Ahmed

Philip Peter Moltmann

Valeriy Zhuravlev

Xavier DeGuillard

Techniques that enable a hypervisor to (1) maintain shared memory pages and (2) handle memory accounting for VMs that are suspended to and resumed from the volatile memory of a host system are provided. Regarding (1), the hypervisor can maintain shared memory pages in volatile memory across the suspend-to-memory and resume-from-memory operations, without having to save their reference counts. Regarding (2), the hypervisor can keep track of the volatile memory reserved and consumed by VMs as they are suspended and resumed, without erroneously double counting that memory.

Handling memory accounting when suspending and resuming virtual machines to/from volatile memory

Techniques for efficiently purging non-active blocks in an NVM region of an NVM device using virtblocks are provided. In one set of embodiments, a host system can maintain, in the NVM device, a pointer entry (i.e., virtblock entry) for each allocated data block of the NVM region, where page table entries of the NVM region that refer to the allocated data block include pointers to the pointer entry, and where the pointer entry includes a pointer to the allocated data block. The host system can further determine that a subset of the allocated data blocks of the NVM region are non-active blocks and can purge the non-active blocks from the NVM device to a mass storage device, where the purging comprises updating the pointer entry for each non-active block to point to a storage location of the non-active block on the mass storage device.

Efficiently purging non-active blocks in NVM regions using virtblock arrays

Systems and methods are described for encrypting a swap file in a computer system. The swap file can be encrypted by a background process executing on the computer system. Processing of paging swapping operations occurs independently and separately of the background encryption of the swap file. Processing a page swapping operation can include decrypting or encrypting data to be swapped involved in the paging operation depending on the paging operation and whether or not the data to be swapped is encrypted or not.

In-place encryption of a swap file on a host machine

Techniques for using non-volatile random access memory (NVM) as volatile random access memory (RAM) are provided. In one set of embodiments, a computer system can detect that an amount of free space in a volatile RAM of the computer system has become low and, in response, can add one or more memory pages from an unused portion of an NVM of the computer system to the system's volatile RAM pool. Conversely, the computer system can detect that an amount of free space in the NVM has become low and, in response, can return the one or more memory pages from the volatile RAM pool back to the NVM.

Using non-volatile random access memory as volatile random access memory

Techniques for efficiently purging non-active blocks in an NVM region of an NVM device while preserving large pages are provided. In one set of embodiments, a host system can receive a write request with respect to a data block of the NVM region, where the data block is referred to by a snapshot of the NVM region and was originally allocated as part of a large page. The host system can further allocate a new data block in the NVM region, copy contents of the data block to the new data block, and update the data block with write data associated with the write request. The host system can then update a level 1 (L1) page table entry of the NVM region's running point to point to the original data block.

Efficiently purging non-active blocks in NVM regions while preserving large pages

Techniques for efficiently purging non-active blocks in an NVM region of an NVM device using pointer elimination are provided. In one set of embodiments, a host system can, for each level 1 (L1) page table entry of each snapshot of the NVM region, determine whether a data block of the NVM region that is pointed to by the L1 page table entry is a non-active block, and if the data block is a non-active block, remove a pointer to the data block in the L1 page table entry and reduce a reference count parameter associated with the data block by 1. If the reference count parameter has reached zero at this point, the host system purge the data block from the NVM device to the mass storage device.

Efficiently purging non-active blocks in NVM regions using pointer elimination

Memory data for a virtual machine can be stored in a swap file, which is comprised of storage blocks. A defragmentation procedure can be performed on a thin swap file while the virtual machine is still running. The described defragmentation procedure traversing a page frame space of the virtual machine, identifying candidate page frames, relocating the swapped page, and updating the page frame. Resulting unused storage blocks are released to the storage system. A data structure for aiding the defragmentation process is also described.

Swap file defragmentation in a hypervisor

Examples provide a page-fault latency feedback metric to determine performance of workloads or virtual machines (VMs) running on a VM host in a cluster. A hypervisor induces page-faults by varying a memory limit associated with a VM. Page-fault latencies are measured at each of the varying memory limits. A performance loss occurring at each page-fault latency is measured and converted to a performance score. A page-fault translation table is constructed based on the page-fault latencies and assigned performance scores. When a page-fault occurs during execution of a workload on a VM host in the cluster, a cluster manager maps the page-fault latency associated with the page-fault to a performance score in the page-fault translation table. The cluster manager computes a current workload performance or VM performance based on the page-fault latency and the performance score.

Page-fault latency directed virtual machine performance monitoring

A computer system provides for rapid power-on operations on virtual machines (VMs) with a virtual memory space including a reservation from machine memory and a small or no swap size. When the computer system powers on a VM, the computer system creates a physical memory space for the VM with a size larger than the minimum memory reservation for the VM and a swap space with a size less than the difference between the size of the virtual memory space and the minimum memory reservation. Subsequently, the computer system iteratively decreases the size of the physical memory space for the VM and increases the size of the swap space for the VM until the size of the physical memory space equals the minimum size of the memory reservation, which may be the amount of the virtual space that is guaranteed to be backed by machine memory.

Rapid virtual machine power-on with iterative swap space reservation

A system and method are disclosed for improving operation of a memory scheduler operating on a host machine supporting virtual machines (VMs) in which guest operating systems and guest applications run. For each virtual machine, the host machine hypervisor categorizes memory pages into memory usage classes and estimates the total number of pages for each memory usage class. The memory scheduler uses this information to perform memory reclamation and allocation operations for each virtual machine. The memory scheduler further selects between ballooning reclamation and swapping reclamation operations based in part on the numbers of pages in each memory usage class for the virtual machine. Calls to the guest operating system provide the memory usage class information. Memory reclamation not only can improve the performance of existing VMs, but can also permit the addition of a VM on the host machine without substantially impacting the performance of the existing and new VMs.

Tracking guest memory characteristics for memory scheduling

A technique for efficient swap space management creates a swap reservation file using thick provisioning to accommodate a maximum amount of memory reclamation from a set of one or more associated virtual machines (VMs). A VM swap file is created for each VM using thin provisioning. When a new block is needed to accommodate page swaps to a given VM swap file, a block is removed from the swap reservation file and a block is added to the VM swap file, thereby maintaining a net zero difference in overall swap storage. The removed block and the added block may be the same storage block if a block move operation is supported by a file system implementing the swap reservation file and VM swap files. The technique also accommodates swap space management of resource pools.

System and method for efficient swap space allocation in a virtualized environment

Page data of a virtual machine is represented for efficient save and restore operations. One form of representation applies to each page with an easily identifiable pattern. The page is described, saved, and restored in terms of metadata reflective of the pattern rather than a complete page of data reflecting the pattern. During a save or restore operation, however, the metadata of the page is represented, but not the page data. Another form of representation applies to each page sharing a canonical instance of a complex pattern that is instantiated in memory during execution, and explicitly saved and restored. Each page sharing the canonical page is saved and restored as a metadata reference, without the need to actually save redundant copies of the page data.

Growing community of inventors

Santa Clara, CA, United States of America

Ishan Banerjee