[ale] Anyone know if this is true?

Thu Oct 13 11:51:34 EDT 2011

So can you consider a presentation of your findinds and perhaps some
testing?
:-)
On Oct 13, 2011 10:52 AM, "Ron Frazier" <atllinuxenthinfo at c3energy.com>
wrote:

> **
> Hi guys,
>
> This thread has prompted me to do a bit of research to try to see if I can
> find a consensus on the swap size issue.  At the moment, it seems like ask
> 100 people and get 100 different opinions.  I haven't uncovered enough data
> to tabulate and summarize it at this point.  I'm pretty sure my linux
> machines have plenty of swap for applications.  I have 8 GB of swap on two
> machines which have 8 GB of RAM.  If I look at the system monitor program in
> Gnome, it looks like the swap is rarely ever touched.  By the way, having 8
> GB of RAM in a laptop is a nice, new, liberating experience for me.  It's
> really nice to be able to open several dozen browser tabs and a dozen or
> more applications without the machine even breathing too hard.  This is my
> first laptop capable of that.  I also have 8 GB of swap on a machine with 4
> GB of RAM, so it should be sitting pretty, so to speak.  I haven't found
> anything that says extra swap is harmful.  What I don't know, is whether the
> two 8 GB machines would be able to hibernate (suspend to disk) properly, if
> the swap is equal to the RAM.  I may have to increase the swap on those to
> 10 GB - 12 GB.  This is not an issue in Windows since it uses a separate
> hibernate file.
>
> In my research, I found this article (
> http://lukasz.szmit.eu/2009/11/compcache-swap-on-linux-desktop.html ).
> The article is a bit old, but this talks about a fascinating project called
> Compcache.  Here's a quote from the page:
>
> ---> quote on <---
>
> Compcache is an open source project implementing an innovative approach to
> swap. This has been done before, but not for swap. Users of DOS and early
> Windows versions will remember DoubleSpace/DriveSpace, which was used to
> virtually expand available disk space, by storing files in a compressed
> form. Compcache does exactly that, but for swap, by creating a new block
> device in the system which interfaces with the special compressed memory
> region in RAM. On the plus side, Compcache can also be configured to use an
> alternative swap device when the RAM swap area is full.
>
> ---> quote off <---
>
> I think that is a really cool idea for low resource machines.  While I
> don't know if I'll ever use it, since my modern machines have a decent
> amount of RAM, it could really benefit older, smaller machines.  For
> example, I have an old IBM Thinkpad with 160 MB (yes MB) of RAM.  I've
> pretty much retired the machine.  It does run a GUI based version of Linux,
> just barely, but is painfully slow.  The old 300 MHz processor doesn't help
> much either.  I think I have an old version of Lubuntu on it.  Anyway, this
> type of technology could give the machine more breathing room by compressing
> the memory, so it would be like having 256 MB of RAM.  I also have an old
> Toshiba laptop which is topped out at 1 GB or RAM.  Both Ubuntu 10.04 and
> Windows XP run pretty well.  However, I could compress 512 MB of RAM and
> then effectively have 512 MB or normal RAM and 1 GB of swap.
>
> Here's the link for the Compcache project:
> http://code.google.com/p/compcache/
>
> Here's an interesting quote from their site: "With compcache at hypervisor
> level, we can compress *any* part of *guest* memory transparently."
>
> Now, while I'll admit I don't understand all the implications of that
> statement, it looks like you could essentially compress all the RAM if
> running a lightweight hypervisor and running your OS as a guest.
>
> The project website also points out that embedded systems could benefit
> from the technology, where you have to justify every chip you put into a
> device.
>
> Finally, here is an interesting quote from the original article:
>
> ---> quote on <---
>
> On my desktop, a Dell Precision S390 with 2GB DDR2 RAM and a Maxtor Diamond
> Max 9 80GB drive, I am getting the following hdparm results (average of
> three runs) for my disk swap, and my compcache swap:
>
>    - Swap on disk: 58MB/s
>    - Compcache swap: 557MB/s
>
> An order of magnitude better bandwidth at no expense? I like that.
>
> ---> quote off <---
>
> I like that idea too.  I'd like to know what you guys think of this
> concept.
>
> Sincerely,
>
> Ron
>
> On 10/13/2011 8:58 AM, Rich Faulkner wrote:
>
> For me depends upon the system as to swap size, but if I plan on using
> hibernation features I have swap just over the size of RAM as in 1-1/2 times
> as the general (old) rule that I've followed...generally a couple of gigs
> for a desktop and I leave it at that.  Being as I'm only building desktops
> and laptops lately I'm not speaking to servers.  An interesting experiment
> is to do test installs to various system configs and see what a given distro
> will do for a default installation.  I consider this a benchmark from the
> developers on an "ideal" configuration given the hardware provided.    RinL
>
>
> On Thu, 2011-10-13 at 08:45 -0400, Scott Castaline wrote:
>
> On 10/12/2011 09:40 PM, Tavarvess Ware wrote:
> >
> > Scott I read the ram x 2= swap in my Linux classes as well and have
> > generally followed that, but with memory soaring as it has lately i am
> > starting to rethink that.  A system 48gigs of memory would be 96 in
> > swap..... I wonder if te old format has changed and I haven't heard yet.
> >
> I only go RAM x 2 = swap for the 1st 2 GB of RAM so 2GB RAM = 4GB swap.
>  From there on it's RAM x 1 = swap so 4GB RAM = 6GB swap. So your 48 GB
> of RAM = 50GB swap, and yup that's one hell of a lot of swap space.
> >
> > On Oct 12, 2011 9:32 PM, "Scott Castaline" <skotchman at gmail.com
> > <mailto:skotchman at gmail.com <skotchman at gmail.com>>> wrote:
> >
> >     On 10/12/2011 04:14 PM, planas wrote:
> >     > On Wed, 2011-10-12 at 15:13 -0400, Geoffrey Myers wrote:
> >     >> 'Just so you all know, when determining how much space to assign to
> >     >> swap: Swap isn't just used for paging or virtual memory
> >     management; swap
> >     >> is also used by power management for suspend-to-disk
> >     (hibernation). '
> >     >>
> >     >> I seriously don't know, so I'm asking.
> >     >>
> >     >
> >     > I have seen that a good swap size is ~1.5x the RAM.
> >     > --
> >     > Jay Lozier
> >     > jslozier at gmail.com <mailto:jslozier at gmail.com <jslozier at gmail.com>>
> >     >
> >     >
> >     >
> >     > _______________________________________________
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> >     > Ale at ale.org <mailto:Ale at ale.org <Ale at ale.org>>
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> >     I remember from somewhere that upto 2GB use 2.0x RAM above 2GB of
> >     RAM go
> >     with 1:1 ratio so 4Gb RAM = 6GB swap. I don't remember why 2x on the
> >     first 2GB and this goes back to when 4GB was a lot on pre-configured
> >     retail boxes. So like Geoffrey I can't see having 18GB of swap for a
> >     16GB machine.
> >
>
>
>
> --
>
> (PS - If you email me and don't get a quick response, you might want to
> call on the phone.  I get about 300 emails per day from alternate energy
> mailing lists and such.  I don't always see new messages very quickly.)
>
> Ron Frazier
> 770-205-9422 (O)   Leave a message.
> linuxdude AT c3energy.com
>
>
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