Is swap really needed when RAM's aplenty

Andrew Haley aph at
Fri Aug 20 14:57:20 UTC 2010

On 08/20/2010 03:36 PM, Aaron Konstam wrote:
> On Thu, 2010-08-19 at 16:15 -0500, Michael Hennebry wrote:
>> On Thu, 19 Aug 2010, JD wrote:
>>> Problem comes as Michael explains, that when a process needs a large
>>> "physically contiguous" chunk of memory, it might not be available.
>>> That said, usually, requests for physically contiguous memory is only
>>> needed when wanting to map very large number of DMA pages for
>>> doing direct physical I/O.
>>> Otherwise, a process itself does not need to have physically contiguous
>>> pages. Only the virtual space allocated to that "malloc" or large buffer
>>> declaration in a program, is contiguous.
>> Why would malloc or a large buffer declaration
>> require physically contiguous memory?
> I have te equally interesting question? Why you think malloc allocates
> memory blocks in the swap area.

JD didn't say that.

He said that when a process needs a large physically contiguous chunk of memory,
you may need to use swap space to move other processes out of the way.


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