MMAP

The mmap modules are used for fast memory transfers between client and server when both reside on the same host.

Implementations

| Component | Link | |-------------------|----------------------------------------------------------------------------------------------------| | client | xpra.client.mixins.mmap | | client connection | xpra.server.source.mmap | | server | xpra.server.mixins.mmap |

Capabilities

The client and server should expose the following capabilities in their hello packet using the clipboard prefix.

The client creates an mmap backing file, writes a random token at a random position within this mmap area and sends the following capabilities:

| Capability | Value | |---------------|--------------------------------------| | file | path to the mmap backing file | | size | size of the mmap area | | token | random token value generated | | token_index | position where the token was written | | token_bytes | length of the token in bytes |

The server should attempt to open the mmap file specified, and verify that the token is found.

To use this mmap file, it must write a new token and return this information to the client. (using the same format, excluding the file and size that the client has already specified)

The client then verifies that the mmap file can be used bi-directionally.

Network Packets

There are no specific mmap packets used, mmap is used as an encoding.

virtio-shmem

Xpra can use mmap with virtio-shmem to speed up connections between a host and guest or even between two guests.

Example steps for host to guest setup:

Documentation: