15-inch MacBook Pro gets hot after replacing HD with SSD

An MBP 15" Mid 2012 is on High Sierra 10.13.6.
Its slowness was down to failing HD sectors, we replaced the HD with a SSD (cloned HD to SSD with CCC). Due to some corrupted pics in the Picture lib, we recovered the pictures lib from backup. Photos app needed for some reason to re-upload all 20,000 pics, this took 24 hrs.
It is now idle, i.e. no user activity but Activity Monitor tells me that the CPU is under almost 100% load, fans on full,
kernel_task writes loads of data, but hardly reads.
photoanalysisd reads a lot, but far, far less writes data.
Overall read/write activity almost constantly on 130-160 MB/sec, for many many hours on end.

What is going on here?

The kernel_task isn’t the problem. It’s just reacting to whatever is causing the heat.


There are a number of tasks that can make a newly installed system both busy and hot. I don’t recall in High Sierra, but Ventura tells you the computer will be slow while it optimises the SSD. In your case, the first suspect would be Photos trying to do face recognition and other nonsense on your 20,000 photos.


It would be so nice if there were a simple method to turn this off. While I use Photos, I do not need any of that face recognition baloney. I’d prefer not to waste CPU cycles on fluff I draw no benefit from. Why isn’t Apple “going green” here?

After another 20 hours it cooled down, for the last 2 hrs I got some form of “normality” back. In total the MacBook took more than 50 hrs of nonstop hard work.

  1. Restoring the Photos Lib from backup,
  2. re-uploading to iCloud,
  3. an endless process that the Photos app showed as “updating”
  4. plus all these unwanted face recognition etc

Only step 1 and possibly step 3 are really needed.

In the old days, when I knew enough Unix to be dangerous (forgotten most of it now, so I’m safe), I seem to recall we could nice a process that was a pig and it wouldn’t be given as many drinks per second from the CPU well. Could you say nice photoanalysisd (or its associated PID) and mitigate the problem?

@fischej Interesting idea, but I’m not confident enough to use a nice command, once this MBP is back in the hands of its owner, I can’t easily make changes anymore.

Unfortunately we are now almost back to square one, periods of normal behaviour, and then again an hour of 100 % CPU usage, high fan speeds and LOADS of data is being read and written. I never switched it off since before I started this thread, I only restarted it a few times.

You can still do that. Just know that -20 is a high priority. +20 is low. You have to be root (use sudo) to use minus priorities.

Check PID
ps -ef|grep <name of proc>

Found PID
renice +20 <number>

Check priority look for PRI
ps -ef -l

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The strange story went on for a few more days. The picture thing was overcome at some point, but Apple MAIL took now all the energy. We made numerous attempts to fix the only IMAP account we need. Deleting the mail index files relatively deep in the library gave us a new and hopefully not corrupted mail index in the sqlite3 DB. MAIL then started to download all of the emails, despite the fact that they are already on the MacBook. So be it. Let’s call it a re-sync. However it doesn’t finish the task, for every attempt it stops somewhere, CPU on 100%, for 24 hrs and more. HUGE amounts of data were read and written. Many times the size of the entire mailbox.

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