Whenever someone complains about a slow computer, the first thing I check is how many Chrome tabs they have open. Chrome hogs memory like no other. For users, this means Chrome is snappy and responsive, but oftentimes it comes at the expense of crowding out other programs. To get an idea of how much memory Chrome is really using, I wrote a quick bash oneliner.

Why does Chrome Hog Memory?

An article posted to Hacker News recently brought some light to the question of why Chrome and Firefox suck up so much memory: Adblock Plus. The general idea is that the excessive use of iframes in most websites today ramps up the amount of processing that Adblock Plus has to do, driving memory usage through the roof. For more specifics, check out the rest of of the article.

The Oneliner

For the impatient, here’s the code. It uses standard Unix tools:

$ ps -ev | grep -i chrome | awk '{print $12}' | awk '{for(i=1;i<=NF;i++)s+=$i}END{print s}'

Pretty isn’t it? If you want to save this as an alias for handy use, add this line to your ~/.bashrc (or appropriate configuration file):

alias chromemem="ps -ev | grep -i chrome | awk '{print \$12}' | awk '{for(i=1;i<=NF;i++)s+=\$i}END{print s}'"

It outputs a percentage. Here’s the alias in action:

$ chromemem
60

Explanation

There’s a lot of good stuff going on here, so let’s take it step-by-step.

First, we’ll need a program that tells us memory usage. I’m sure there are many, but I’m familiar with ps. After checking out the man page for a few options, I came up with ps -ev, to show all information about all processes. Maybe wasteful, but it works.

$ ps -ev
  PID STAT      TIME  SL  RE PAGEIN      VSZ    RSS   LIM     TSIZ  %CPU %MEM COMMAND
 3473 S      0:54.92   0   0      0  3579092 301244     -        0   6.7  7.2 /Applications/Google Chrome.app/Contents/Frameworks/...
  365 S      3:03.17   0   0      0  3920732 206808     -        0   0.3  4.9 /Applications/Google Chrome.app/Contents/Frameworks/...
  983 S      1:29.23   0   0      0  3560272 193860     -        0   0.1  4.6 /Applications/Google Chrome.app/Contents/Frameworks/...
  395 S      0:13.11   0   0      0  2824936 141644     -        0   0.0  3.4 /Applications/Google Chrome.app/Contents/Frameworks/...
  422 S      0:27.22   0   0      0  3345796 130796     -        0   0.0  3.1 /Applications/Google Chrome.app/Contents/Frameworks/...
  ...

Notice that there’s a convenient column describing memory usage as a percentage of total available memory, as well as what command is being run in that process. Let’s make sure that we’re looking at only the processes running some sort of Chrome service before totaling up the memory. We can find these lines with ps -ev | grep -i chrome (the -i means case-insensitive). Due to the way I clipped the previous sample output, nothing changes in the first five lines, but rest assured: we’re only looking at Chrome processes now.

Now it’s time to get rid of all the other nonsense that we included with ps -ev. Luckily, there’s a handy tool called awk that makes parsing text by column easy. If we want to print the 12th column (which just so happens to contain the memory consumption!) we can do awk '{print $12}':

$ ps -ev | grep -i chrome | awk '{print $12}'
7.2
5.1
4.6
3.4
3.2
...

Finally, I found myself needing a way to add up a column of numbers. A quick Google search led me to this StackOverflow question, and I picked the awk solution because I knew I could just pipe the input to awk (as opposed to having to do weird hacks to get it to work with a bash for loop):

$ ps -emv | grep -i chrome | awk '{print $12}' | awk '{for(i=1;i<=NF;i++)s+=$i}END{print s}'
60.4

Of course, you could change the last awk command to print out something fancier like

$ ps -emv | grep -i chrome | awk '{print $12}' | awk '{for(i=1;i<=NF;i++)s+=$i}END{print "Chrome is using "s"% of total memory."}'
Chrome is using 60.4% of total memory.

There you have it! Bash oneliners save the day yet again.

Update

After writing this article, I stopped using Ad Block Plus, and I noticed a significant drop in Chrome’s memory usage. Obviously, though, that came at the cost of not blocking ads! Also, from time to time I would encounter a site that seemed sluggish, presumably because of all the ads attempting to be loaded. My simple solution to this was just to disable JavaScript on that page (I use an extension called Quick JavaScript Switcher), but this wasn’t an automated solution.

Then I discovered μBlock, an “efficient blocker for Chromium and Firefox.” The fancy graphs on it’s homepage convinced me to give it a shot, and from what I can tell so far it’s responsive and effective.