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DChabot Author

Level 1

145 points

kernel_task consumes a lot of RAM in early 2011 MBP, sometimes Finder too

Hi,

My old MBP3,1 (late 2007, 2.4 GHz Core 2 Duo) worked quite well with 4 GB of RAM, even after weeks without restarting. In fact, I used all available RAM only on some larger analyses using R, which loads the entire dataset in memory. To be able to run these few analyses faster on my new machine (early 2011 MBP), I bought the 8 GB RAM option.

In Activity Monitor, I noticed something strange. Whereas my old MBP shows kernel_taks as using between 100 and 200 MB of RAM, the new MBP uses about 550 MB just after the machine started up and often shows over 600 after a few hours or days of use. A one year old iMac, again Core 2 Duo with 4 GB of RAM, gives a kernel_task memory usage below 200 MB after weeks of use.

I've not been able to find what kernel_task does. Is this amount (around 600 MB, but it has gone up to 800) normal? Is it managiing the additional number of cores that requires this behind the scenes amount of RAM?

Anyway, I now quite often have more than 4 GB of RAM in use even when I have only a few applications running (not even including R!), which surprises me.

Also today, after moving a lot of files back and forth between an external drive and the new MBP, after emptying the garbage can that contained a hefty number of files and doing a first Time Machine backup, the Finder ended up using 2,4 GB of RAM according to Activity Monitor. I have never seen anything like this (although I admit not having Activity Monitor on all the time). Even after the backup was finished and the external drive disconnected (in fact the machine was left idling for a few hours) cpu usage was down to nearly zero, the Finder kept its 2.4 GB of RAM. I restarted and the new RAM usage for the Finder was 26 MB. I have a screen shot showing the 2.4 GB, but I could not find a way to attach it to this message. I can send it by email on request. I don't think this Finder behavior was normal.

Somewhat worried,

Denis

MacBook Pro 2.2 GHz i7, 8 GB RAM, Mac OS X (10.6.6)

Posted on Mar 16, 2011 12:04 AM

216 replies

Jul 2, 2011 2:20 PM in response to DChabot

Has the Thunderbolt Firmware update helped this issue for anyone else? On my MBP, kernel_task was taking up ~600 MB after restarts, but "just" ~480 MB after updating.

wyager

Level 1

8 points

Jul 2, 2011 4:06 PM in response to davebwells

@LSUAMDG

I have 4 gigs. I'll probably keep it that way until 16 gigs doesn't cost so much.

@davebwells

I just updated, no difference for me.

Jul 10, 2011 8:02 AM in response to wyager

Any news here?

Got the same problem. Early MBP 2011 with 4 GB RAM.

kernel_task is always around 500-600 MB. Thundelt Firmware update is installed.

LSUAMDG

Level 1

0 points

Jul 10, 2011 11:38 AM in response to DChabot

@ rodknocker

no new news. just waiting until Lion comes out.

I wonder if people who have the sandy bridge in the new iMacs are having this same problem?

Jul 11, 2011 5:10 AM in response to LSUAMDG

Same behavior on a newly purchased MBP, 8GB RAM.

The amount of RAM doesn't concern me, it seems that the kernel uses its own algorithm for allocating it.

It is the constant CPU consumption that makes me suspect something is not optimal.

wyager

Level 1

8 points

Jul 11, 2011 11:52 AM in response to rares.azoth

Care to elaborate, rares.azoth? Most processes don't use an "algorithm" for allocating RAM-they just allocate it dynamically, whenever they create or release an object. How much CPU is your using? Mine sticks around 1-5%. IMO, a few percent of 1/8th of the processor is pretty good.

Jul 11, 2011 3:23 PM in response to wyager

kernel_task is not a regular process, it is a reporting task that represents specific kernel activities, such as allocating and releasing memory pages, task scheduling etc.

To my understanding (see apple documentation ) the amount of memory that you see in the Real Memory column of this particular process (kernel_task) includes memory pages that are releasable by the kernel (under a LRU policy) when required (by other processes).

If you add another column (Private Memory) in Activity Monitor you will actually find the memory that is allocated to that specific process alone. (in my case is 50 MB).

On my machine, the CPU consumption of the kernel_task "process" and its threads averages at 3-4% which only started to happen after upgrading to 10.6.7. It is too high and in my opinion indicative that something is not going well, perhaps a kext is not functioning well. Curious to measure it after doing a clean install of Lion in the following days.

wyager

Level 1

8 points

Jul 11, 2011 6:10 PM in response to rares.azoth

Sure, but it doesn't really plan out its ram use... it just drops whatever it's not using anymore (under LRU policy, like you said).

My kernel_task has 167 megs of private ram, and "only" 470 megs real memory. Our processes seem to be using RAM differently.

FYI, none of the loaded kexts on my computer seem to be using using more than a few megs of ram. Kextstat and USB Prober will tell you how much RAM each loaded kext is using.

LSUAMDG

Level 1

0 points

Jul 21, 2011 12:18 PM in response to DChabot

So anyone get 10.7 yet? If so, does it have any effect?

Jul 21, 2011 12:24 PM in response to LSUAMDG

No effect :-(

I upgraded to 8 GB yesterday.

wyager

Level 1

8 points

Jul 21, 2011 5:52 PM in response to rodknocker

Bummer! I'm downloading it from the app store right now, I'll see if it makes any difference. Lately, however, I haven't noticed k_t taking up more than 600 megs, so maybe a recent update helped me a bit. Still too much, of course.

Jul 21, 2011 11:46 PM in response to wyager

In my post from 10.07.2011, my MBP had 4 GB installed. With Lion GM.

Memory usage around 500-600 MB.

On 20.07.2011 i upgraded to 8 GB.

As you can see the kernel_task memory usage growed up to 800-950 MB.

For me it looks like this: The more RAM i install, the more ram takes the kernel_task 😢😢😢

wyager

Level 1

8 points

Jul 22, 2011 12:14 AM in response to DChabot

No help. Maybe a little worse, actually... Oh well, at least they added a little more hardware support to Lion. OpenCL now works on the new MBPs as far as I can tell.

Jul 22, 2011 12:17 AM in response to wyager

Maybe we could try to boot into 32-bit kernel?

eww

Level 9

53,028 points

Jul 22, 2011 7:12 AM in response to rodknocker

For me it looks like this: The more RAM i install, the more ram takes the kernel_task 😢😢😢

Yes, that has always been true. Just as running more applications benefits from more RAM, so does the OS.

kernel_task consumes a lot of RAM in early 2011 MBP, sometimes Finder too