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Re: Swap



Hybernate to disk.
When asking to hybernate to disk, the system does the following. It flushes all buffers, It looks to discard ram buffer space that has no open files and writes itself to disk, along with some restart information.
Your 4 gigs of ram are probably consisting of 2 gigs of available to reuse buffer space.
On restart from hybernate,
Generally the system is reloaded, the clock is corrected, and any open file pointers are reopened along with the restore of that buffer. Then space is made available for additional cacheing.

If you use Ubuntu, Fedora, Centos, SUSE, Tumbleweed, or any current system, the installer program will use an algorithm to create a separate conservative sized swap partition.

Every few weeks I delete my Linux partitions on the SSD and I reinstall (another ) system. The reason I do it that way is simple -- I look at a lot of software, and it is easier to reinstall the system with what I want to keep, than to uninstall what I do not want to keep.
And I stay with the 7.8gigs swap for my 8 gigs of ram.
 
Regards

 Leslie
Mr. Leslie Satenstein
Montréal Québec, Canada




From: Michael <codejodler@gmx.ch>
To: debian-laptop@lists.debian.org
Sent: Saturday, February 6, 2016 5:08 AM
Subject: Re: Swap

Jos,

Originally, i wantded to wrtie "if we take Stefan seriously, then something like 2/3 of RAM size should be 99.99% enough; and you'll probably never see the 0.01% worst case in your lifetime".

But then, with modern harddrives, who cares about one or two G more or less :)

* As a sidenote, what happens if we put hibernation swap on a fast external USB 3.0 pendrive device ... doesn't that mean the data is safe even if the laptop gets snatched ?


> That's right. I'm able to hibernate, suspend and run many applications (I
> didn't try things like creating a squashfs ) at the same time using 3.8 GB
> of swap and 4gb of RAM.
>
> I was thinking of using 6gb swap for my new installation. But now I think
> in the new installation in my new SSD,  I will just use a 4gb max swap
> partition. What do you say ?
> On 06-Feb-2016 7:54 AM, "Tom Dial" <tddial@comcast.net> wrote:
>
> > Thank you; I did not know that, and it makes for a significant swap size
> > reduction in nearly all cases of a desktop or laptop workstation.
> >
> > The other points, I think, are not much changed.  For the case Jos
> > Collin presented initially, (and noting his mention in another branch of
> > 175 MB actually used) 2GB swap likely is quite enough.
> >
> > Tom
> >
> >
> > On 02/04/2016 03:41 PM, Stefan Monnier wrote: 
> > >> option, swap is where the memory image is put, and it should be at least
> > >> as large as real memory. 
> > >
> > > Actually no: when hibernating, the requirement is that the currently
> > > unused swap space (which should usually be pretty much the whole swap
> > > space), be large enough to contain a *compressed* form of a *part* of
> > > the RAM (the parts that can be skipped are those which would never be
> > > moved to swap anyway, such as the caches that hold a copy of data which
> > > is already available elsewhere on disk).
> > >
> > > So it doesn't need to be as large as RAM.  In many cases, the amount of
> > > swap space used by hibernation less than 1/3 of RAM.
> > >
> > >
> > >        Stefan
> > >
> > > 
> >
> > 




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