Sporkybay

Thank you @testdasi, I was just coming here to post that I solved this last night by following these exact steps. I also blew away my Plex Codecs folder, and upgraded my UnRaid to 6.5.3. Now transcoding is distributing the load between the 8 cpus I wanted. I must have misunderstood SpaceInvader One in his Pt3 video about Performance Tuning, because I thought he said that snapping a docker was possible to isolated cores. Like I said in my OP, I knew I had to have done something wrong. With a specific caveat though, because all of this idea for cpu isolation started with all my transcodes funneling into CPU0 and people reporting buffering issues. I wasn't using pinning, hence, why I tried to move the load to other CPUs in the first place. Thank you everyone!

Plex Transcoder.

@Hoopster Lol. Thanks for the link. I've chased that rabbit a while before coming here for some of everyone's wisdom. No other docker or process is acting like this, which makes me think it may be "unique" to my Plex install. I haven't tried upgrading, but maybe I'll give it a go. Never done one before... How hard could it be? I'll be googling/reading furiously once I get home. In your opinion/experience, should I remove the Alpha_Support from SysLinux before upgrading? Or is it one of those, "I guess we'll find out what the button does when I push it" things?

I have Quality at Auto, with the x264 preset at Very Fast. Quality is primarily 720p, but the file I used for testing is a brutal 1080p one (you know those Chris Nolan films).

Okay, I need to reach out to the hive mind for ideas. I work in IT, so I've got enough experience to realize that it's probably something I've done (or didn't do), but I can't figure out what. Help me Obi Wan(s). So, I'm running LinuxServer Plex, and everything is good in the hood, when I decide to try hardware transcoding (running i7-8700k). Found some directions, modified go, syslinux, tossed the correct extra parameter into the docker, and bam, my cpu utilization dropped significantly (like 15% to 5% or something), and tatulli was reporting (HW) in the transcode. I could run multiple transcode streams, and everything seemed fine. But then one day people started complaining about buffering, and that surprised me, because my old i7-3770k (running Plex on W7) wouldn't have had these hiccups running 3-4 transcodes, so why would this box be doing it... Looking at the dashboard, it seemed to be routing all my transcodes to CPU0. If I disabled the hardware transcode, it seemed to distribute back to all 12 cpus. Well, i figured it wasn't optimal to do that, so I started looking at CPU pinning. So, watched a few videos put up by SpaceInvader One, and thought to optimize my server. Set up isolcpus to block off CPU 2-5,8-11 so I could reserve that for Plex. Okay, now everything is running in CPU 0-1,6-7. Add cpuset-cpus to Plex, and... Everything is running through CPU2. Regardless of if Hardware transcode is on or not, it's all CPU2. Installed cAdvisor, and sho nuff, everything is CPU2. All those other cores are just napping. I tried reformatting to cpus=2,8,3,9... etc, and same thing. I remove the pinning, and everything routes back through the main cpus (leaving the 8 logical cores alone)... I'm just at a loss here. I removed the hw transcode "check" in the plex gui, and the "--device /dev/dri:/dev/dri" from the docker parameters, but it's making no difference. I didn't remove the original stuff I added to the go or syslinux, and maybe that's part of the issues? I dunno. Anyone have any ideas? unspork-diagnostics-20180909-2255.zip

@Hoopster, thanks for the feedback. Edited my original post with details/diagnostics.

So, I followed a conglomeration of directions I pieced together from the forums (thank you everyone!), and was able to get Hardware transcoding working on my i7-8700k based Unraid box. Really, no issues when I watch things most of the time, but I recently started having more and more users require transcoding, and some complaints started to come in about excessive buffering. So, I finally started to pay attention to things, and a noticed that when transcoding is running, it's really only using CPU0 (and ignoring the other 11 CPUs). I didn't specifically set up core isolation at any point in my set up, so I'm wondering if this is just a property of hardware transcoding? ---Edit--- You're 100% right @Hoopster , totally neglected anything important for troubleshooting. My bad. Attached the diagnostics, but a quick overview of your questions: I'm on 6.5.2, and I did enable i915 alpha_support in the syslinux.cfg. I did edit the go file to include the chmod chown on the i915. The only extra parameter I have going in linuxserver/plex is "--device /dev/dri:/dev/dri". Other than figuring out how to make a bond0 so my double NIC card worked in aggregate, I haven't modded any other flash files. And I don't think I have messed with cpu isolation (didn't know how to even do that until I started troubleshooting the behavior I was seeing). unspork-diagnostics-20180908-0747.zip

THANK YOU!!! I've been going through the ringer for 3 hours trying to figure this out before I finally came across this post (finally got the perfect combo of search). Now I can HW transcode!