Frederic , thanks for quick reply. You are touching QOS tier. Let us take a scenario to better understand me. pod A has 7000 shared as requests ( --cpu-shares) but no limits. Pod B has 1000 shares as requests and 3000 as limits. In CPU contention situation, how scheduling and QOS works in Kubernet world?
Will Pod A get more CPU time then Pod B? or POD B get its guaranteed cpu slices first before CPU scheduling pod A since it doesn’t have limits? -- Srinivas Kotaru From: Frederic Giloux <[email protected]> Date: Thursday, March 22, 2018 at 9:22 AM To: Srinivas Naga Kotaru <[email protected]> Cc: users <[email protected]> Subject: Re: Limits for CPU worth? Vs benefits Hi Srinivas, here are a couple of scenarios where I find setting limits useful: - When I do performance tests and want to compare results between runs, setting CPU limits=CPU requests give me confidence that the CPU cycles available between the runs were more or less the same. If you don't set a limit or have a higher limit anything between the two values is best effort and depend on what is happening on the node, including resources consumed by other pods. - You may also set CPU limits when you want to differentiate between applications that are able to consume the "extra" CPU cycles, the ones that haven't been "requested". Or you may want to limit how much "extra" these applications can get. An example is batch processing, which can use lots of CPU cycles but you may not mind it to finish a bit earlier or later. I hope this helps. Regards, Frédéric On Thu, Mar 22, 2018 at 4:59 PM, Srinivas Naga Kotaru (skotaru) <[email protected]<mailto:[email protected]>> wrote: CPU requests enforced using shares. Even in contention situation, kernel still scheduling based on shares and depending on shares, pods getting their own shares and never lead to cpu bottleneck or high load on the nodes. Basically it never cause noise Neighbour problem. I understand cpu limits enforced using cpu quota and helps throttling. Question or argument is do we still need when cpu shares already doing their job well both non-contention and contention situation? What extra benefits it bringing? Need some clarity for in the context of noise neighbors problem and prevent node going down or prevent one or few bad pods disturbing every pod in node? Basically looking for what is benefit of having or not having cpu limits for pods ? Sent from my iPhone _______________________________________________ users mailing list [email protected]<mailto:[email protected]> http://lists.openshift.redhat.com/openshiftmm/listinfo/users -- Frédéric Giloux Principal App Dev Consultant Red Hat Germany [email protected]<mailto:[email protected]> M: +49-174-172-4661<tel:+49-174-172-4661> redhat.com<http://edhat.com> | TRIED. TESTED. TRUSTED. | redhat.com/trusted<http://redhat.com/trusted> ________________________________________________________________________ Red Hat GmbH, http://www.de.redhat.com/ Sitz: Grasbrunn, Handelsregister: Amtsgericht München, HRB 153243 Geschäftsführer: Paul Argiry, Charles Cachera, Michael Cunningham, Michael O'Neill
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