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<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt">Hello!<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt">My team uses Pacemaker as a cluster manager. Our configuration is large enough, therefore we have lots of resources and constraints for them.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt">While using Pacemaker we noticed that its decision making algorithm works slow for large configurations. We gathered some flame graphs to determine where the problem could be.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt">And according to the flame graph for schedulerd which is attached to this email we can say that the execution of decision making part takes a lot of time.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt">In particular, stage7 which is responsible for applying ordering constraints and updating actions for all resources is complicated enough.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt">We did some investigation of Pacemaker code and we have some assumptions how we can potentially speed-up schedulerd.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt">So I’d very appreciate if you share your thoughts and knowledge on this topic.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt">The main concern is that currently schedulerd re-calculates all meta-data once notification from controld is received.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt">This requires querying the entire CIB and analyzing it in schedulerd code applying all constraints from scratch. However, it can be inefficient in case of small CIB changes.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt">BTW, controld receives CIB diff, but still provides schedulerd with entire CIB.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt">So, what if we could pass CIB diff to schedulerd instead of the entire CIB and modify schedulerd logic in order to store all previous meta-data and apply diff to it somehow?<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt">Knowing what changed (or what type/part of configuration changed) can potentially allow us to skip processing of some (large or small part of) resources and actions.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt">Could you tell me please, what do you think about it? Perhaps you already faced this issue and had some ideas or even patches for schedulerd to speed it up.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt">The version of Pacemaker we us is 2.0.1+20190417.13d370ca9 (release 3.6.1).<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt">Thanks a lot in advance!<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt">--<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt">Denis<o:p></o:p></span></p>
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