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https://issues.apache.org/jira/browse/GUACAMOLE-1776?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17714267#comment-17714267
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Christopher Speck commented on GUACAMOLE-1776:
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We'll submit a pull request with the change described
> 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: Major
> 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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