[jira] [Commented] (GUACAMOLE-668) Preferring JPEG due to lower CPU usage - controlling guacd behaviour via some kind of preferences

["Michael Jumper (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/GUACAMOLE-668?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16700297#comment-16700297 ] 

Michael Jumper commented on GUACAMOLE-668:
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Simply measuring instantaneous CPU usage is a poor metric, particularly with respect to subjective remote desktop performance. See: https://mail-archives.apache.org/mod_mbox/guacamole-user/201803.mbox/%3CCALKeL-Oc6xnj99D9G9mE3aAS1Bj6xL%3DRnCM%3D052VCeMn%3DdBs9g%40mail.gmail.com%3E

I don't believe forcing JPEG or WebP for all updates is an option that should exist at the guacd level. I would also argue that the option should not exist even at the connection parameter level. The surface implementation is intended to be clever enough to choose the most appropriate compression, so explicitly forcing JPEG/WebP would be a step backward.

Assuming that you are seeing subjective performance issues when PNG is used for a particular series of updates, and subjective performance improvements when JPEG/WebP are used instead, the proper solution would be to improve the heuristics selecting between PNG and JPEG/WebP, not to entirely disable a component of Guacamole's optimization subsystem under the assumption that PNG will always underperform. Experience has shown that PNG actually performs better in terms of subjective responsiveness for non-photographic graphical updates, and that choosing JPEG/WebP in a case where PNG would be a better choice results in uncomfortable lag. With this in mind, I think any approach that eliminates PNG would be inherently incorrect.

{quote}
What do you think about adding such an ability and what would be the best approach to implement this? If you provide guidance, I can try to implement it.
{quote}

If you have questions about Guacamole, please use the mailing lists. JIRA is meant as an issue tracker, not a forum. I would advise against implementing this at all for the reasons above, but if you would like to discuss this further (ideally taking a step back and considering alternative approaches that don't indiscriminately eliminate PNG), I suggest opening a thread on dev@guacamole.apache.org.


> Preferring JPEG due to lower CPU usage - controlling guacd behaviour via some kind of preferences
> -------------------------------------------------------------------------------------------------
>
>                 Key: GUACAMOLE-668
>                 URL: https://issues.apache.org/jira/browse/GUACAMOLE-668
>             Project: Guacamole
>          Issue Type: Wish
>          Components: guacd
>            Reporter: Andrzej Dorobisz
>            Priority: Major
>
> In our HPC center, we observe that guacamole-server (guacd) is generating quite high CPU-usage even if only one session is currently processed (it reaches 100% when moving window back and forth).
> We have tested that using JPEG instead of PNG in "{{__guac_common_surface_flush_}}_" (_src/common/surface.c_) noticeably decreases the CPU usage. When WebP is available it performs better than PNG but still it's slower (in terms of CPU usage) than JPEG.
> We believe that user running _guacd_ should be able to choose which format is preferred - without recompilation. Our first idea was to use _guacd.conf_ for passing such a preference, but we see that it is not so simple. We have to store such a preference somewhere and then pass it to VNC client which is calling {{__guac_common_surface_flush}} function.
> -------
> What do you think about adding such an ability and what would be the best approach to implement this? If you provide guidance, I can try to implement it.



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