[FAQ] Scheduling of session workunits


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Message boards : Server backend and mirrors : [FAQ] Scheduling of session workunits

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Message 5888 - Posted: 25 May 2007, 6:58:31 UTC
Last modified: 9 Dec 2007, 13:06:59 UTC

Question:
Why does my session have a \' \' (zzZ) after it in the status list?

Answer:
To make it possible to fairly schedule all work on the renderfarm, and divide the resources amongst all of the artists who would like to utilize it, it is sometimes necessary to (either temporarily or permanently) give a particular session a lower priority than others. This is usually the case if the session is both very lengthy, has a high number of parts per frame and each of these parts take a lot of resources to compute.
The icon means that the session has been put into a special state called \"Background rendering\". In this state workunits will be sent out less frequently if there are other sessions around.
Another implication is that the scheduler will use a different scheduling strategy for that session - it will try to send out one (or a few) results per workunit at a time. This means that it takes longer for each workunit to reach its quorum, but in return the entire session will get a 33% speedup because the CPU power is spent more wisely. When it takes longer to reach the quorum it will also take longer to get credit for the work done on that workunit - the credit won\'t be lost, though, you will be able to find it on the pending credit page and it will be granted as soon as the workunit reaches its quorum.

It works in the way that each workunit will be given several different priorities for each of its results. This means that some results for that workunit will be rendered before others. Therefore the chance that the workunit will validate before the system needed to send out the extra workunits is high.
This can theoretically boost performance by as much as 50% on lengthy sessions (that take a factor >3 of the initial deadline to complete).

Also background priority scheduling works well with multiple background sessions mixed with normal ones. If a normal (short) session appears it will get a short priority boost to complete almost as fast as if no background sessions were being simultaneously rendered.


Question:
Why does my session have a \' \' (zzZ) after it in the status list?

Answer
Sometimes it is necessary to completely stop rendering a specific session until all other sessions have been rendered. Sleeping sessions do not even share rendering time with background sessions.
Once a sleeping session finally does start rendering it is usually turned into a background session.
Many, but not all, test sessions issued by the project will be running in this state to avoid interfering with the ongoing actual sessions.
Sleeping sessions appear with a red \'zzZ\' icon.

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Message 5889 - Posted: 25 May 2007, 6:58:43 UTC
Last modified: 25 May 2007, 7:17:58 UTC

Please only reply to this thread if you have any additions to the Scheduling FAQ - if you experience any issues with missing credit or wrongly scheduled sessions please create a new thread (or search and use an existing thread) instead.

Profile Istvan Burbank
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Message 8884 - Posted: 27 Dec 2008, 13:50:07 UTC

How does this fit into the high/low priority rendering? if someone pays for high priority, putting them into background mode basicly renders those 999 extra SCS they paid worthless.

~or am I missing something? is it tiered so the above states are per priority so the high priorities will never go below the low priorities but can be background compared to other high priorities? - Istvan.

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Message 8891 - Posted: 27 Dec 2008, 19:09:02 UTC - in response to Message 8884.

Question:
Does sleeping and background priority interfere with the existing priority for a session?

Answer:
Yes. A normal session will be running at either high or low priority and will loose that priority when it is changed into either sleeping or background mode. It may return to its previous priority when the scheduling issues have been cleared.

Question:
If someone pays for high priority. Does putting the session into background mode render those extra SCS spent worthless?

Answer:
This is a hypothetical answer since the extra SCS were never actually charged to your account in BURPv.2 and in BURPv.3 the scheduling and priority system is completely different. But hypothetically the answer is \"yes\". These FAQs will be updated once the new system is in place.


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Message boards : Server backend and mirrors : [FAQ] Scheduling of session workunits