OS X startup disk has no more space available for application memory

Most operating systems (including OS X) will start using the hard drive when RAM is used up. This happens when you either don't have enough RAM, or a rogue process takes it all. This also slows down your computer big time.

Either way, Activity Monitor will tell you wich process is the culprit.

If I remember correctly the answer was "kernel_task", whatever that is, which I only found by selecting "all processes" instead of the default "my processes"

You're the first person to report an issue with kernel_task here. What version of OS X are you using? How much "Real Mem" did Activity Mon say kernel_task was using? Post a screenshot if you can.

kernel_task always takes a lot of memory which I *THINK* can be released to the system if other apps need more memory, so even though it may have been the first in your process list, it may not have been the culprit. Can you remember roughly how much memory it was using?

Whee wrote:

kernel_task always takes a lot of memory

No.

10.8.3, 8G Ram installed. System uptime 9 days.

Guess what, 650mb is a lot.

https://www.google.ca/search?q=kernel_task+memory&ie=utf-8&oe=utf-8&aq=t&rls=org .mozilla:en-US:official&client=firefox-a

I disagree

I disagree with you disagreeing.

With most apps using less than 200mb, kernel_task using 650mb in comparison is a lot. It will often be at the top of the list for memory usage. Yet, it is completely normal.

What is your Page Out number?

1.6mb

Your Mac has needed to swap 1.6mb to disk since you last restarted. That is not a problem: memory is being used effectively on your Mac. If you want to get that down to Zero add more Ram.

650mb is not alot - and clearly not enough to cause a system with gigabytes of RAM to start swapping out to disk. Check out the screen shot from a user above who's Safari process was using almost 6gb of RAM - THATS a lot. For me, it was an HP printer driver that was consuming GB of RAM, slowing down my parents computer.

After isolating Firefox (I suspect it was an addon or specific website Java scripts) I have found Sophos AV consume huge memory (any amount of free disk space can be used up) when doing a full system scan. The only alternative I have found is to stop the scan and run it some other time - and if I am lucky the full scan goes through.

Read what I said again and read it in its context.

The guy suspected kernel_task to be the culprit because it's what was using the most RAM.

kernel_task being the process that uses the most RAM is not suprising, because most apps (or I should say "processes") use less than 200MB and compared to most apps, which use less than 200MB, 650MB is a lot. It's especially "a lot" considering that over 80% of processes use less than 100MB. And my point was that even if it used a lot of RAM relative to the other processes, that doesn't make it the culprit.

I'm not saying "650mb is a lot for kernel_task" or even "650mb is a lot relative to total RAM", I'm saying "650mb is a lot compared to most processes" and that it's not uncommon for it to be the process that uses the most RAM. Again, read again.

Hey yeah I think you are right, it is currently using 846 MB and maybe (i can't recall) I had already shut down safari and turned off wireless when I looked at the activity monitor. It's pretty crap that an application that came in teh box, so to speak, could cause such problems. Thre was another process which was using 100% of my CPU but I can't remember what it was called.