Do Small Memory Leaks Matter Anymore?

Question

With RAM typically in the Gigabytes on all PC\'s now, should I be spending time hunting down all the small (non-growing) memory leaks that may be in my program? I\'m talking abo

Answer 1

A memory leak really depends on several things:

• How often the leak happens
• How much memory is lost each time
• How long is the program going to run

For example, if you lose 40 bytes every time a task happens, and that task happens when the program starts, then nobody cares. If you lose 40Mb every time the program starts, then it should be investigated. If you lose 40 bytes every frame in your video or game engine, then you should look into that, because you'll lose 1.2kB each second, and after an hour you would have lost almost 4Mb.

It also depends on how long the program is going to stick around for. For example, I have a small calculator app, that I open, run a calculation in, and then close again. If that app loses 4Mb in it's run, then it doesn't really matter, because the OS will reclaim that lost memory once I close it. If the hypothetical video/game engine mentioned earlier lost 4Mb an hour, and it ran a demo unit, for several hours a day at a stand at a convention, then I'd look into it.

An example of a famous memory leak is Firefox, which lost a lot of memory in it's earlier versions. If your browser leaked memory 10 years ago, then you probably wouldn't care. You shut down the computer every day, and you while running the browser you only had one page up at a time. Today I just let my laptop go to standby, and I never close Firefox. It is open for weeks at a time, and I have at least 10 tabs open at any given time. If memory leaks every time a tab is closed, then that is going to build up to a larger leak now than it did 10 years ago, and so it is more important.

Answer 2

Memory leaks are never OK in any program, however small it may be. Slowly they will add up to fill up your entire memory. Suppose you have a calling system which leaks about 4 bytes of memory per call it handles. You can handle say, 100 calls a second (this is a very small number), so you end up leaking 400 bytes a second or 400x60x60(1440000B) an hour. So, even a small leak is not acceptable. And if you dont know the source of the leak then it may be some real big issue and you end up having buggy software. But, essentially it boils down to the questions like, for how much time the program runs and what number of times the leak happens. So, it may be ok it leaks a very small amount and is not repeated but still the leak may be a small part of a bigger problem. So, I feel that memory leaks are never ok.

Answer 3

It depends on the nature of your application. I work primarily with web sites and web applications. So by most definitions, my application "runs" once per request. Code that leaks a few bytes per request on a high volume site can be catastrophic. From experience, we had some code which leaked a few kb per request. Added up, that caused our web server worker processes to restart so often it caused minute-long outages throughout the day.

But web applications (and many other kinds) have an indefinite lifespan - they run continuously, forever. The shorter-lived your application, the better. If each session of your application has a finite and reasonably predictable end point, there's of course a reasonable amount of leakage you can tolerate. It's all about the ROI.

Answer 4

Leaks are bugs.

You probably have other bugs too.

When you ship a product, you ship it with known bugs. When you choose which (of the known) bugs to "fix" versus "ship with", you do so based on the cost and risk to fix versus the customer benefit.

Leaks are no different. If it's a small leak that happens during an infrequent operation in a non-server app (e.g. an app that runs for minutes or hours and then shuts down), it might be "ok" in the same way any other bug is ok.

Actually, leaks can be kinda different in one important way, which is that if you are shipping a library/API, you really should fix them, because the customer benefit is enormous (otherwise all your customer 'inherit' your leak, and will be phoning you just as you have to do to talk to 3rd party vendor now).

Answer 5

That's like asking if there was a crack in a dam is it ok? NO! NEVER! Avoid memory leaks as if your life depends on it because when your application grows and gets more use that leak is going to turn into a flood and sooner or later someone or something is going to drown in it. Just because you can have lots of memory doesn't mean that you can take shortcuts with your code. Once you find a leak do what you can to resolve it and if you can't solve it make sure you keep coming back to it until it's fixed.

If you can't resolve the leak then try to see if you can clean up after it. The bigger issues come when the leak is repetitive.

Last note: if you ever hand the software to someone else and that leak is still there it may be a long time before someone else finds and/or fixes it.

Answer 6

Yes. Leaks matter. If your apps runs 24x7x365 and handles a few thousands transactions per second, a few bytes turns into gigabytes rapidly.