Christopher Speck created GUACAMOLE-1776:
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Summary: Base64 encoding of image/binary data results in excessive
syscalls that can degrade performance
Key: GUACAMOLE-1776
URL: https://issues.apache.org/jira/browse/GUACAMOLE-1776
Project: Guacamole
Issue Type: Improvement
Components: guacamole-server
Affects Versions: 1.3.0
Reporter: Christopher Speck
Attachments: vtune_profile.png
When sending image/binary data to a socket the data is base64 encoded and
buffered in a way that incurs an excessive number of system calls which can
degrade performance.
This occurs in {{socket.c}} where {{guac_socket_write_base64}} ends up calling
{{guac_socket_write}} in a tight loop, once for every 3 bytes being encoded.
The system calls this incurs are:
* {{clock_gettime}} via {{guac_timestamp_current}}
* {{{}pthread_mutex_rdlock{}}}/{{{}unlock{}}} via
{{guac_socket_fd_write_handler}}
Attached an image of VTune profiling which shows that very little time is spent
in guac_socket_fd_write_buffered but a lot of time is spent in the syscalls
outlined.
Introducing a buffer(~1kb) to append data being encoded prior to writing to the
socket results in a performance increase, reducing the time spent on the
syscalls. For relative comparison in our test we started with 13fps and by
introducing the buffer saw an increase to 23fps.
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