Abstract: Methods, systems, and computer programs for managing physical memory in a host of a virtual infrastructure are presented. One method includes an operation for detecting that a guest physical page (GPP) of a virtual machine (VM) is a balloon page. The GPP, previously mapped to a machine page (MP), is re-mapped to a shared page of memory in order to free the MP, such that a read to the GPP causes a read to the shared page of memory. Further, the method includes an operation for detecting a write to the shared page of memory after the re-mapping of the GPP to the shared page, where the write to the shared page is caused by a write to the GPP. After detecting the write, all balloon pages created by the VM are reset in order to reset the balloon application in the VM.

Abstract: Miss rate curves are constructed in a resource-efficient manner so that they can be constructed and memory management decisions can be made while the workloads are running. The resource-efficient technique includes the steps of selecting a subset of memory pages for the workload, maintaining a least recently used (LRU) data structure for the selected memory pages, detecting accesses to the selected memory pages and updating the LRU data structure in response to the detected accesses, and generating data for constructing a miss-rate curve for the workload using the LRU data structure. After a memory page is accessed, the memory page may be left untraced for a period of time, after which the memory page is retraced.

Abstract: Large pages that may impede memory performance in computer systems are identified. In operation, mappings to selected large pages are temporarily demoted to mappings to small pages and accesses to these small pages are then tracked. For each selected large page, an activity level is determined based on the tracked accesses to the small pages included in the large page. By strategically selecting relatively low activity large pages for decomposition into small pages and subsequent memory reclamation while restoring the mappings to relatively high activity large pages, memory consumption is improved, while limiting performance impact attributable to using small pages.

Abstract: Large pages that may impede memory performance in computer systems are identified. In operation, mappings to selected large pages are temporarily demoted to mappings to small pages and accesses to these small pages are then tracked. For each selected large page, an activity level is determined based on the tracked accesses to the small pages included in the large page. By strategically selecting relatively low activity large pages for decomposition into small pages and subsequent memory reclamation while restoring the mappings to relatively high activity large pages, memory consumption is improved, while limiting performance impact attributable to using small pages.

Abstract: A computer implemented method for reducing the latency of an anticipated read of disk blocks from a swap file in a virtualized environment. The environment includes a host swap file maintained by a host operating system and a guest swap file maintained but a guest operating system. First, the method identifies a sequence of disk blocks that was written in the guest swap file. The method then detects within the sequence of blocks a first disk block that contains a reference to a second disk block that is stored in the host swap file. The method then replaces the first disk block in the guest swap file with the second disk block.

Abstract: A computer implemented method for reducing the latency of an anticipated read of disk blocks from a swap file in a virtualized environment. First, the method identifies a sequence of disk blocks that was written in a guest swap file. The method then detects a first reference within the sequence of blocks that references a first disk block stored in a host swap file and a second reference within the sequence of blocks that references a second disk block stored in the host swap file. The method then moves the second disk block to a location in a host swap file that is adjacent to the first disk block. In some examples, the first block and second block are both moved to a new location in the host swap file where they are adjacent to one another.

Abstract: A lightweight technique for sharing memory pages within a virtual machine (VM) is provided. This technique can be used on its own to implement intra-VM page sharing or it can be augmented with sharing across VMs. Memory pages whose content can be described by some succinct grammar, such as a regular expression or simple pattern, are identified for sharing within a VM. If the content of a page matches some simple pattern, it is proposed to share such a page, but only in the scope of the VM to which it belongs, i.e., intra-VM sharing. All other pages, i.e., those that are not simple patterns, can be candidates for sharing in the scope of all currently active VMs, i.e., inter-VM sharing. Either fully functional page sharing across VMs and/or page sharing in the context of each VM can be implemented.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: A process for lazy checkpointing is enhanced to reduce the number of read/write accesses to the checkpoint file and thereby speed up the checkpointing process. The process for restoring a state of a virtual machine (VM) running in a physical machine from a checkpoint file that is maintained in persistent storage includes the steps of detecting access to a memory page of the virtual machine that has not been read into physical memory of the VM from the checkpoint file, determining a storage block of the checkpoint file to which the accessed memory page maps, writing contents of the storage block in a buffer, and copying contents of a block of memory pages that includes the accessed memory page from the buffer to corresponding locations of the memory pages in the physical memory of the VM. The storage block of the checkpoint file may be compressed or uncompressed.

Abstract: A process for lazy checkpointing a virtual machine is enhanced to reduce the number of read/write accesses to the checkpoint file and thereby speed up the checkpointing process. The process for saving a state of a virtual machine running in a physical machine to a checkpoint file maintained in persistent storage includes the steps of copying contents of a block of memory pages, which may be compressed, into a staging buffer, determining after the copying if the buffer is full, and upon determining that the buffer is full, saving the buffer contents in a storage block of the checkpoint file.

Abstract: Memory performance in a computer system that implements large page mapping is improved even when memory is scarce by identifying page sharing opportunities within the large pages at the granularity of small pages and breaking up the large pages so that small pages within the large page can be freed up through page sharing. In addition, the number of small page sharing opportunities within the large pages can be used to estimate the total amount of memory that could be reclaimed through page sharing.

Abstract: Miss rate curves are constructed in a resource-efficient manner so that they can be constructed and memory management decisions can be made while the workloads are running. The resource-efficient technique includes the steps of selecting a subset of memory pages for the workload, maintaining a least recently used (LRU) data structure for the selected memory pages, detecting accesses to the selected memory pages and updating the LRU data structure in response to the detected accesses, and generating data for constructing a miss-rate curve for the workload using the LRU data structure. After a memory page is accessed, the memory page may be left untraced for a period of time, after which the memory page is retraced.

Abstract: A process for lazy checkpointing a virtual machine is enhanced to reduce the number of read/write accesses to the checkpoint file and thereby speed up the checkpointing process. The process for saving a state of a virtual machine running in a physical machine to a checkpoint file maintained in persistent storage includes the steps of copying contents of a block of memory pages, which may be compressed, into a staging buffer, determining after the copying if the buffer is full, and upon determining that the buffer is full, saving the buffer contents in a storage block of the checkpoint file.

Abstract: A process for lazy checkpointing is enhanced to reduce the number of read/write accesses to the checkpoint file and thereby speed up the checkpointing process. The process for restoring a state of a virtual machine (VM) running in a physical machine from a checkpoint file that is maintained in persistent storage includes the steps of detecting access to a memory page of the virtual machine that has not been read into physical memory of the VM from the checkpoint file, determining a storage block of the checkpoint file to which the accessed memory page maps, writing contents of the storage block in a buffer, and copying contents of a block of memory pages that includes the accessed memory page from the buffer to corresponding locations of the memory pages in the physical memory of the VM. The storage block of the checkpoint file may be compressed or uncompressed.

Abstract: Miss rate curves are constructed in a resource-efficient manner so that they can be constructed and memory management decisions can be made while the workloads are running. The resource-efficient technique includes the steps of selecting a subset of memory pages for the workload, maintaining a least recently used (LRU) data structure for the selected memory pages, detecting accesses to the selected memory pages and updating the LRU data structure in response to the detected accesses, and generating data for constructing a miss-rate curve for the workload using the LRU data structure. After a memory page is accessed, the memory page may be left untraced for a period of time, after which the memory page is retraced.

Abstract: Methods, systems, and computer programs for managing physical memory in a host of a virtual infrastructure are presented. One method includes an operation for detecting that a guest physical page (GPP) of a virtual machine (VM) is a balloon page. The GPP, previously mapped to a machine page (MP), is re-mapped to a shared page of memory in order to free the MP, such that a read to the GPP causes a read to the shared page of memory. Further, the method includes an operation for detecting a write to the shared page of memory after the re-mapping of the GPP to the shared page, where the write to the shared page is caused by a write to the GPP. After detecting the write, all balloon pages created by the VM are reset in order to reset the balloon application in the VM.

Abstract: Methods, systems, and computer programs for managing physical memory in a host of a virtual infrastructure are presented. One method includes an operation for detecting that a guest physical page (GPP) of a virtual machine (VM) is a balloon page. The GPP, previously mapped to a machine page (MP), is re-mapped to a shared page of memory in order to free the MP, such that a read to the GPP causes a read to the shared page of memory. Further, the method includes an operation for detecting a write to the shared page of memory after the re-mapping of the GPP to the shared page, where the write to the shared page is caused by a write to the GPP. After detecting the write, all balloon pages created by the VM are reset in order to reset the balloon application in the VM.

Abstract: A lightweight technique for sharing memory pages within a virtual machine (VM) is provided. This technique can be used on its own to implement intra-VM page sharing or it can be augmented with sharing across VMs. Memory pages whose content can be described by some succinct grammar, such as a regular expression or simple pattern, are identified for sharing within a VM. If the content of a page matches some simple pattern, it is proposed to share such a page, but only in the scope of the VM to which it belongs, i.e., intra-VM sharing. All other pages, i.e., those that are not simple patterns, can be candidates for sharing in the scope of all currently active VMs, i.e., inter-VM sharing. Either fully functional page sharing across VMs and/or page sharing in the context of each VM can be implemented.