Chrome memory measurement now almost flat for longer test runs

Question

In order to check our web application for memory leaks, I run a machine which does the following:

• it runs automated End-to-End tests over (almost) the entire application in Chrome
• after each block of tests, it goes to a state of the web application where almost nothing happens
• it triggers gc(); for garbage collection
• it saves totalJSHeapSize, and usedJSHeapSize to a file
• it plots out the results for each test run to a graph

That way, we can see how much the memory increases and which are the problematic parts of our application: At some point the memory increases, at some point it decreases. Till yesterday, it looked like this:

Bright red (upper line): totalJSHeapSize, light red (lower line): usedJSHeapSize

Yesterday, I updated Chrome to version 69. And now the chart looks quite different:

The start and end amount of memory used (usedJSHeapSize) is almost the same. But as you can clearly see, the way it changes over the course of the test (ca. 1,5h) is quite different.

My questions are now:

• Is this a change in reality or in measurement? I.e. did Chrome change its memory handling? Or just the way it puts out memory values via totalJSHeapSize, and usedJSHeapSize?
• Concerning memory leaks, is it good news or bad news for me? Like: Before I had dozens of spots where memory increases, now I have just three. Is this true? Or are the memory leaks in the now flat areas still there and hidden?

I'm also thankful for any background information on how Chrome changed its memory measurement.

Some additional info:

• The VM runs under KUbuntu 18.04

• It's a single web page application done with AngularJS 1.6

• The outcome of the memory measurement is quite stable - both before and after the update of Chrome

EDIT: It seems this was a bug of Chrome version 69. At least, with an update to Chrome 70, this strange behavior is gone and everything looks almost as before.

Answer 1

I don't think you should be worry about it. This can happen due to the memory manager used inside the chrome. You didn't mentioned the version of your first memory graph, possibility that the memory manager used between these two version is different. Chrome was using the TCMalloc which take the large chunk of memory from the OS and manage it, once the memory shortage happenned with TCMalloc then it ask again a big chunk of memory from OS and start managing it. So the later graph what you are seeing have less up and downs (but bigger then previous one) due to that. Hope it answered your query.

As you mentioned that

The outcome of the memory measurement is quite stable - both before and after the update of Chrome

You don't need to really worry about it, the way previously chrome was allocating memory and how it does with new version is different(possible different memory manager) that's it.