Vmware, Inc.

Kapil Arya

Alexander T Garthwaite

Yury Baskakov

Maxime Austruy

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.

Techniques for reducing read I/O latency in virtual machines

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.

In a virtual machine, swap activities of a hypervisor and a guest OS are reconciled so that redundant input-output operations (IOs) can be avoided and a synchronous response time of the virtual machine improved. This is achieved with a map of memory pages to blocks of storage. For a write IO to write contents of a memory page into a target block, the map is examined to see if it contains a valid entry for the memory page. If the map contains the valid entry, the write IO is prevented from being issued and a data structure is updated so that subsequent IOs to the target block is redirected from the target block to a block that is associated with the physical memory page in the valid entry. On the other hand, if the map does not contain the valid entry, the write IO is issued.

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Kapil Arya