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What is "kernel_task"?
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iBBS Addict
Picture of CHunter
posted
Nowhere to be found is there an
explanation online of what this is,
and why it uses so much RAM.

Anyone really know?
 
Posts: 1619 | Registered: June 16, 2002Reply With QuoteReport This Post
iBBS Addict
Picture of James R. Cutler
posted Hide Post
The kernel task is the heart of OS X on your Mac. Think of it as the conductor directing various instruments which make up the processes on the computer. It starts and stops various operations, manages the allocation of CPU time to each process or thread, and manages real and virtual memory, controlling which is used by what. It also contains all of the kernel extensions (kexts) which are specialized pieces of code responsible for specific devices or actions like connecting I/O devices.

Every process or thread running on your system runs in a system context which includes, among other things, real and virtual memory, stack (short term memory used when changing context within a process or thread), and, various administrative items like the current user of the process. The kernel keeps track of all this in tables. Virtual Memory is the way each Process is allocated blocks of memory addresses which are then assigned real memory as required to actually run code. Swapping is done by the kernel when there is insufficient real memory to contain all the requested real memory space to continue running a process. The kernel memory manager component may need to swap as it changes context between processes. The possible simultaneous threads running is limited by the CPU and multi-threading capabilities of the hardware.

Some significant things to remember about the kernel task are, in simplified terms:

  • Without the kernel task, nothing happens.
  • The kernel keeps track of everything using tables which amount to lists which may point to other lists.
  • The more process and threads running, the more list space is needed in the kernel.
  • The more physical memory there is, the more list space is needed in the kernel.
  • The more virtual memory there is, the more list space is needed in the kernel.
  • The more I/O is active, the more list space is needed in the kernel.


You can see the effect of multiple processes on kernel memory and CPU time by watching it in Activity Monitor as you launch Safari and open multiple simultaneous windows. After quitting Safari, the usage drops back to about where it was before launching Safari.

Another discussion of the OS X Kernel is http://apple.stackexchange.com...-does-kernel-task-do

Enjoy.
 
Posts: 1968 | Registered: January 02, 2003Reply With QuoteReport This Post
iBBS Addict
Picture of CHunter
posted Hide Post
Jim,
Thanks for this perfect answer.
There are a few million Mac users online
looking for this explanation.
 
Posts: 1619 | Registered: June 16, 2002Reply With QuoteReport This Post
iBBS Addict
Picture of CHunter
posted Hide Post
Ah, Jim, Smile
What function is com.apple.IconsServicesAgent?
It is a RAM hog as well.
 
Posts: 1619 | Registered: June 16, 2002Reply With QuoteReport This Post
iBBS Addict
Picture of James R. Cutler
posted Hide Post
quote:
What function is com.apple.IconsServicesAgent?

com.apple.IconServicesAgent part of the new caching mechanisms in Mavericks. Per user instances run to manage caching of icons for each login and some system processes. You can see the effect of applications on IconServicesAgent CPU and memory by watching the Activity Monitor while launching Safari and opening lots of new windows and then quitting Safari.

In the absence of some fault, CPU usage should remain small and, for accounts not logged in or otherwise active, memory consumption should also be small. Once a program like Safari downloads lots of pages with lots of icons, memory usage might increase from 2-3 MB to 320 MB, depending on exactly which pages have been viewed. I've been logged on for a few days and used Safari repeatedly on a relatively constant set of web sites. Currently com.apple.IconServicesAgent is using 0% CPU and 317.1 MB memory.

.
 
Posts: 1968 | Registered: January 02, 2003Reply With QuoteReport This Post
iBBS Addict
Picture of CHunter
posted Hide Post
Thanks.
As I normally have lots of tabs open
in Safari, this process balloons to
the 500MB+ range at any given time.
Very Helpful.
 
Posts: 1619 | Registered: June 16, 2002Reply With QuoteReport This Post
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