Re: No swap can be dangerous (was Re: swap on RAID (was Re: swp -Re: ext3 journal on software raid))

[Jesper Juhl]

On Thu, 6 Jan 2005, Andrew Walrond wrote:

> On Thursday 06 January 2005 17:46, Mike Hardy wrote:
> >
> > You are correct that I was getting at the zero swap argument - and I
> > agree that it is vastly different from simply not expecting it. It is
> > important to know that there is no inherent need for swap in the kernel
> > though - it is simply used as more "memory" (albeit slower, and with
> > some optimizations to work better with real memory) and if you don't
> > need it, you don't need it.
> >
> 
> If I recollect a recent thread on LKML correctly, your 'no inherent need for 
> swap' might be wrong.
> 
> I think the gist was this: the kernel can sometimes needs to move bits of 
> memory in order to free up dma-able ram, or lowmem. If I recall correctly, 
> the kernel can only do this move via swap, even if there is stacks of free 
> (non-dmaable or highmem) memory.
> 
> I distinctly remember the moral of the thread being "Always mount some swap, 
> if you can"
> 
> This might have changed though, or I might have got it completely wrong. - 
> I've cc'ed LKML incase somebody more knowledgeable can comment...
> 

http://kerneltrap.org/node/view/3202


-- 
Jesper Juhl


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