[jira] [Updated] (GUACAMOLE-1776) Base64 encoding of image/binary data results in excessive syscalls that can degrade performance

["Nick Couchman (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/GUACAMOLE-1776?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Nick Couchman updated GUACAMOLE-1776:
-------------------------------------
    Priority: Minor  (was: Major)

> 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
>            Priority: Minor
>         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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