RE: RAM and swap partition

RE: RAM and swap partition

[james miller]

Let me pose the RAM question in another way to see if it can elicit a 
generic, "rule-of-thumb" response this way. If a person uses their 
computer as a sort of personal workstation using a fairly recent distro 
and requires that it have an Xwindows gui, using applications like web 
browsers, email clients, wordprocessing software and maybe Gimp on 
occassion, at what point would such a person need to have a swap 
partition? In other words, can it be stated in somewhat generic terms 
"if said user had less than X MB RAM, they will definitely need a swap 
partition"? And what about guidelines for swap partition size in such a 
case: can such be stated as well? Like, say, "if this individual has 
only 32 MB RAM, he should have a 64 MB swap partition" or "if he has 64 
MB RAM he'll only need a 64 MB swap partition"?

Thanks, James

>===== Original Message From Chuck Gelm <nc8q@gelm.net> =====
>Ditto to what Ray said.
>
> Perhaps you could run your system with a 'swap file' and see
>how big it ever gets.  Then make a swap partition just that size
>or a little larger.  ;-)
>
> My current firewall-router (aDSL to 100 Mb LAN) has 32 megabytes
>  of RAM and has not used any swap memory, AFAICR.
> Another workstation with 64 M of RAM has used 3 M of swap.
> Another workstation with 160 M of RAM has used 2 M of swap.
> Another laptop with 16 M of RAM, XFfree86 v4.0.3, and I just
>  ran Netscape v4.77 under fvwm95, loaded a small web page,
>  has used 2.6 M of swap.
>
> IMHO, it depends.  ;-)
>
>HTH, Chuck
>
>Ray Olszewski wrote:
>>
>> At 01:15 PM 12/8/02 +0000, Rolf Edlund wrote:
>> >Originally to: james niland
>> >
>> >
>> >  jn> I know some people who run happily without a swap at all.
>> >
>> >How low RAM can I use, without running a swap ? Can I for example
>do it on
>> >a 486
>> >with 4 MB RAM ?
>>
>> The way you ask this question, it has no real answer. How little
>memory a
>> system can run with depends on what tasks it is doing. And the
>choice of
>> CPU is pretty much irrelevant to this question (its only slight
>relevance
>> is in the smaller size of CPU-specific kernels).
>>
>> That said ... running any sort of Linux system in less than 8 MB of
>real
>> (not swap) RAM poses special challenges ... most modern distros
>can't even
>> install on such systems (only Slackware, I think, still offers a
>"low
>> memory" install option) and you won't be able to do much with such
>a
>> system. In practice, the smallest systems I've ever run without
>swap were
>> 486s with 16 MB of RAM, and that was for special purpose systems
>like
>> routers. While these days I routinely run my workstations without a
>swap
>> partition, they have at least 256 MB of RAM.
>>
>> --
>> -------------------------------------------"Never tell me the
>odds!"--------
>> Ray Olszewski                                   -- Han Solo
>> Palo Alto, California, USA                        ray@comarre.com
>>
>-----------------------------------------------------------------------------
--
>>
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RE: RAM and swap partition

[Ray Olszewski]

At 01:22 PM 12/9/02 -0500, james miller wrote:
>Let me pose the RAM question in another way to see if it can elicit a
>generic, "rule-of-thumb" response this way. If a person uses their
>computer as a sort of personal workstation using a fairly recent distro
>and requires that it have an Xwindows gui, using applications like web
>browsers, email clients, wordprocessing software and maybe Gimp on
>occassion, at what point would such a person need to have a swap
>partition? In other words, can it be stated in somewhat generic terms
>"if said user had less than X MB RAM, they will definitely need a swap
>partition"? And what about guidelines for swap partition size in such a
>case: can such be stated as well? Like, say, "if this individual has
>only 32 MB RAM, he should have a 64 MB swap partition" or "if he has 64
>MB RAM he'll only need a 64 MB swap partition"?

I cannot help you with "definitely" answers. But I can tell you the rules 
of thumb I've used when setting up workstations (which don't exactly use 
the mix of stuff you ask about, but come close).

If I am setting up a system with 256 MB or less of  RAM, I include a swap 
partition. If the system is using a modern hard disk (that is, one that is 
20 GB or more), I make swap twice the size of RAM; if I is using a small, 
old hard disk, I make it equal to RAM for sizes close to 256, twice RAM for 
significantly smaller sizes (trading off filesystem space against swap 
space is itself a judgment call for 128 and 192 MB systems).

If I were setting up a system with more than 256 MB of RAM and a modern 
hard disk (and this is all I really do these days for workstations), I 
*create* a swap partition equal in size to RAM, but I do not make it 
active. I have never actually found a need for a swap partition on a 
workstation with 256 MB of RAM or more, but that way I have one in reserve 
if I need it.

As a general matter, if you are running a system that uses swap regularly 
(rather than very rarely, say just when you custom compile apps or 
kernels), the performance hit you are taking probably justifies paying the 
relatively small cost of adding RAM if you can (of course, some older mobos 
still in circulation, such as older E-Machine Celeron boards, won't take 
more than 256 MB, limiting your options). And I've seen occasional 
segfaults that *seem* to be associated with swap access in recent 2.4.x 
kernels, so I try to avoid even rare uses of swap on my newer (512+ MB RAM) 
systems.

It's hard for me to think sensibly about what I'd do on a system with, say, 
16 or 32 MB of RAM, because I can't seriously imagine setting up such a 
system as a workstation today (though I use such systems for specialized 
purposes ... routers, mainly). Back when I ran such systems, I used swap 
that was twice the size of RAM, and that's probably what I'd do today up to 
64 MB, maybe even up to 128 MB.

Bottom line, though ... there are no hard and fast guidelines these days 
for "best practice" swap setup.


--
-------------------------------------------"Never tell me the odds!"--------
Ray Olszewski					-- Han Solo
Palo Alto, California, USA			  ray@comarre.com
-------------------------------------------------------------------------------

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Re: RAM and swap partition

[ichi]

Ray Olszewski wrote:
> 
> It's hard for me to think sensibly about what I'd do 
> on a system with, say, 16 or 32 MB of RAM, because I 
> can't seriously imagine setting up such a system as a 
> workstation today 

You might be surprised at the number of people today trying
to install Linux on computers with less than 32mb RAM.  It
not unusual for Windows users to try Linux on a dusty old PC 
(rather than risk their precious Windows machine).  Also, 
there are still quite a few laptops in regular use with less 
than 32mb RAM.  

One of the advantages of Linux is that it still quite usable
on old hardware.  A light X runs pretty well on 12mb RAM -- 
I even know of some people running X with 4mb RAM (*shudder*).

Cheers,
Steven

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Re: RAM and swap partition

[Chuck Gelm]

It depends.

james miller wrote:
> 
> Let me pose the RAM question in another way to see if it can elicit a
> generic, "rule-of-thumb" response this way. If a person uses their
> computer as a sort of personal workstation using a fairly recent distro
> and requires that it have an Xwindows gui, using applications like web
> browsers, email clients, wordprocessing software and maybe Gimp on
> occassion, at what point would such a person need to have a swap
> partition?

 You would need to have a swap partition when your system 
'runs out of' real memory.  It depends on how much memory 
the applications request/need.  There are many, many window
managers from tiny 'twm' to huge KDE & GNOME.  I would guess
that there are small and large 'word processing' software.

 I can run Xwindows, fvwm95, netscape v4.77, in 48 Megabytes
of virtual memory.  It would run much faster if 32 or more
magabytes were real RAM. ;-) However, it does run. 

>             In other words, can it be stated in somewhat generic terms
> "if said user had less than X MB RAM, they will definitely need a swap
> partition"? 

 It depends on what is requesting memory.

>            And what about guidelines for swap partition size in such a
> case: can such be stated as well? Like, say, "if this individual has
> only 32 MB RAM, he should have a 64 MB swap partition" or "if he has 64
> MB RAM he'll only need a 64 MB swap partition"?

  It depends.

 Tell the list what you plan to run and you will probably 
get many suggestions.  ;-)

HTH, Chuck

> Thanks, James
> 
> >===== Original Message From Chuck Gelm <nc8q@gelm.net> =====
> >Ditto to what Ray said.
> >
> > Perhaps you could run your system with a 'swap file' and see
> >how big it ever gets.  Then make a swap partition just that size
> >or a little larger.  ;-)
> >
> > My current firewall-router (aDSL to 100 Mb LAN) has 32 megabytes
> >  of RAM and has not used any swap memory, AFAICR.
> > Another workstation with 64 M of RAM has used 3 M of swap.
> > Another workstation with 160 M of RAM has used 2 M of swap.
> > Another laptop with 16 M of RAM, XFfree86 v4.0.3, and I just
> >  ran Netscape v4.77 under fvwm95, loaded a small web page,
> >  has used 2.6 M of swap.
> >
> > IMHO, it depends.  ;-)
> >
> >HTH, Chuck
> >
> >Ray Olszewski wrote:
> >>
> >> At 01:15 PM 12/8/02 +0000, Rolf Edlund wrote:
> >> >Originally to: james niland
> >> >
> >> >
> >> >  jn> I know some people who run happily without a swap at all.
> >> >
> >> >How low RAM can I use, without running a swap ? Can I for example
> >do it on
> >> >a 486
> >> >with 4 MB RAM ?
> >>
> >> The way you ask this question, it has no real answer. How little
> >memory a
> >> system can run with depends on what tasks it is doing. And the
> >choice of
> >> CPU is pretty much irrelevant to this question (its only slight
> >relevance
> >> is in the smaller size of CPU-specific kernels).
> >>
> >> That said ... running any sort of Linux system in less than 8 MB of
> >real
> >> (not swap) RAM poses special challenges ... most modern distros
> >can't even
> >> install on such systems (only Slackware, I think, still offers a
> >"low
> >> memory" install option) and you won't be able to do much with such
> >a
> >> system. In practice, the smallest systems I've ever run without
> >swap were
> >> 486s with 16 MB of RAM, and that was for special purpose systems
> >like
> >> routers. While these days I routinely run my workstations without a
> >swap
> >> partition, they have at least 256 MB of RAM.
> >>
> >> --
> >> -------------------------------------------"Never tell me the
> >odds!"--------
> >> Ray Olszewski                                   -- Han Solo
> >> Palo Alto, California, USA                        ray@comarre.com
> >>
> >-----------------------------------------------------------------------------
> --
> >>
> >-
> >To unsubscribe from this list: send the line "unsubscribe linux-newbie" in
> >the body of a message to majordomo@vger.kernel.org
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Re: RAM and swap partition

[Chuck Gelm]

It depends.

james miller wrote:
> 
> Let me pose the RAM question in another way to see if it can elicit a
> generic, "rule-of-thumb" response this way. If a person uses their
> computer as a sort of personal workstation using a fairly recent distro
> and requires that it have an Xwindows gui, using applications like web
> browsers, email clients, wordprocessing software and maybe Gimp on
> occassion, at what point would such a person need to have a swap
> partition?

 You would need to have a swap partition when your system 
'runs out of' real memory.  It depends on how much memory 
the applications request/need.  There are many, many window
managers from tiny 'twm' to huge KDE & GNOME.  I would guess
that there are small and large 'word processing' software.

 I can run Xwindows, fvwm95, netscape v4.77, in 48 Megabytes
of virtual memory.  It would run much faster if 32 or more
magabytes were real RAM. ;-) However, it does run. 

>             In other words, can it be stated in somewhat generic terms
> "if said user had less than X MB RAM, they will definitely need a swap
> partition"? 

 It depends on what is requesting memory.

>            And what about guidelines for swap partition size in such a
> case: can such be stated as well? Like, say, "if this individual has
> only 32 MB RAM, he should have a 64 MB swap partition" or "if he has 64
> MB RAM he'll only need a 64 MB swap partition"?

  It depends.

 Tell the list what you plan to run and you will probably 
get many suggestions.  ;-)

HTH, Chuck

> Thanks, James
> 
> >===== Original Message From Chuck Gelm <nc8q@gelm.net> =====
> >Ditto to what Ray said.
> >
> > Perhaps you could run your system with a 'swap file' and see
> >how big it ever gets.  Then make a swap partition just that size
> >or a little larger.  ;-)
> >
> > My current firewall-router (aDSL to 100 Mb LAN) has 32 megabytes
> >  of RAM and has not used any swap memory, AFAICR.
> > Another workstation with 64 M of RAM has used 3 M of swap.
> > Another workstation with 160 M of RAM has used 2 M of swap.
> > Another laptop with 16 M of RAM, XFfree86 v4.0.3, and I just
> >  ran Netscape v4.77 under fvwm95, loaded a small web page,
> >  has used 2.6 M of swap.
> >
> > IMHO, it depends.  ;-)
> >
> >HTH, Chuck
> >
> >Ray Olszewski wrote:
> >>
> >> At 01:15 PM 12/8/02 +0000, Rolf Edlund wrote:
> >> >Originally to: james niland
> >> >
> >> >
> >> >  jn> I know some people who run happily without a swap at all.
> >> >
> >> >How low RAM can I use, without running a swap ? Can I for example
> >do it on
> >> >a 486
> >> >with 4 MB RAM ?
> >>
> >> The way you ask this question, it has no real answer. How little
> >memory a
> >> system can run with depends on what tasks it is doing. And the
> >choice of
> >> CPU is pretty much irrelevant to this question (its only slight
> >relevance
> >> is in the smaller size of CPU-specific kernels).
> >>
> >> That said ... running any sort of Linux system in less than 8 MB of
> >real
> >> (not swap) RAM poses special challenges ... most modern distros
> >can't even
> >> install on such systems (only Slackware, I think, still offers a
> >"low
> >> memory" install option) and you won't be able to do much with such
> >a
> >> system. In practice, the smallest systems I've ever run without
> >swap were
> >> 486s with 16 MB of RAM, and that was for special purpose systems
> >like
> >> routers. While these days I routinely run my workstations without a
> >swap
> >> partition, they have at least 256 MB of RAM.
> >>
> >> --
> >> -------------------------------------------"Never tell me the
> >odds!"--------
> >> Ray Olszewski                                   -- Han Solo
> >> Palo Alto, California, USA                        ray@comarre.com
> >>
> >-----------------------------------------------------------------------------
> --
> >>
> >-
> >To unsubscribe from this list: send the line "unsubscribe linux-newbie" in
> >the body of a message to majordomo@vger.kernel.org
> >More majordomo info at  http://vger.kernel.org/majordomo-info.html
> >Please read the FAQ at http://www.linux-learn.org/faqs
> 
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Re: RAM and swap partition

[ichi]

james miller wrote:
> 
> Let me pose the RAM question in another way to see if
> it can elicit a generic, "rule-of-thumb" response 

I'm happy to give you my personal "rule-of-thumb", 
but that's all it is.  It's not an absolute truth.

Every system gets at least 16mb of total memory.
So, a system with 4mb RAM gets 12mb swap.

Light X installations with slim wm (*not* KDE or Gnome) 
get at least 32mb total memory.  So, a system with 12mb RAM 
gets 24mb swap.

Heavy X installations need RAM.  Lots of RAM.  Swap is
less relevant on such systems.

Cheers,
Steven

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Re: RAM and swap partition

[Heimo Claasen]

Chuck - that swapfile: has it to be created anew just before any
prog/app is run ? Or could I just leave it "on" ?

Well, and then - can I conclude from this that a swap _partition_ is
basically used like a file ?
(Or else: would programs which need swap create their _specific_ files
in a swap partition ?)

-heimo
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Re: RAM and swap partition

[Chuck Gelm]

Heimo Claasen wrote:
> 
> Chuck - that swapfile: has it to be created anew just before any
> prog/app is run ? Or could I just leave it "on" ?

 A swap file, once created, can be left.
However, you will need to restart swap upon each boot.
Perhaps a rc.local script command will do.


> Well, and then - can I conclude from this that a swap _partition_ is
> basically used like a file ?

 Well, maybe a swap file is used more like a partition.  :-|

> (Or else: would programs which need swap create their _specific_ files
> in a swap partition ?)

 A swap file and a swap partition behave as virtual memory,
not as a file.  So let us not try to assign file attributes
to virtual memory (swap) or file attributes to virtual
memory (ramdisk).  User applications do not create swap
or ramdisk.  User applications request memory or create
scratch pad files.  ;-)

 I think.

HTH, Chuck

> 
> -heimo
> -
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Re: RAM and swap partition

[Heimo Claasen]

Ok, ok, Chuck - sure "it depends" ;)
(and oops, hwo do I use a swap _file_ instead of the "prescribed"
partition ?)

From your list, I conclude that it depends on all those six-and-a-half
factors, even if I'm not soooo convinced what for instance, "distro
AND version" (on top of the kernel number), the BogoMIPS or even the
HD speed, would have to do with it.

And then I have this experience with one (notabene experimental) sound
application which just doesn't care for how much swap there is - but
it is a darn memhog in itself: it crashes if the data file (or too many
together) loaded need too much _RAM_, regardless of how large I dimension
the swap.
So this real and practical example would tell me: no swap partition
needed (EXACTLY for this one app.)

Another real-life case is with that not-so-brandnew laptop and its
"small" HD of 2 GB and "poor" RAM (48 MB) installed, where Linux has
to share space with a windoze and a small DOS partition. This runs
vanilla apps in Linux - a GUI + a browser (including the connectivity
gears) + a plug-in pic viewer at most, simultaneously. Here, seen HD
space and RAM available (both hugely enormous, seen from my past-&-present
DOS uses; all real work, including almost all net-work needed, is done
in text mode and in the miniscule DOS compartment), the volume to set
aside for a swap partition is even a "critical" decision.

Then there is one factor which you did not mention but which might be
of decisive importance: if a unit is used by one person, it would most
probably have just one user (and a very few "user accounts" only) and
simultaneous use of different apps would be probably limited or rather,
the user-"system-owner-administrator" could be enabled to establish a
reasonable estimate of the real need for swap space on the perhaps
not-so-enormously-new/big-HD -- _if_ s/he had some ways or indications
for calculating it.

I think this is a reasonable demand, and I'm looking for some means to
answer to this.  So, how would I measure how much swap this kernel or
that application (in combination with what GUI, for instance) would
need, in fact ?

> it may be suggested EXACTLY how much swap space you will need.

Hmm, for that laptop for instance, running yet a much too FAT Mandrake 8.2
with kernel 2.4.18 (because Debian would not find the good video driver
for the trickish LCD). I would gladly dish the mem-(and how much swap-?)
hogging KDE and Nutsrape with it; though, regrettably, it must be able to
run X and a SSL-capable net connection.

I understood James' earlier questions quite similar to what I would ask
for this example; and feel the are still not answered:
> "if said user had less than X MB RAM, they will definitely need a swap
> partition"? And what about guidelines for swap partition size in such a
> case: can such be stated as well? Like, say, "if this individual has
> only 32 MB RAM, he should have a 64 MB swap partition" or "if he has 64
> MB RAM he'll only need a 64 MB swap partition"?

<besides>IMNSO too many of the posts especially on this list here -
where I suppose are precisely quite a lot of "single-users" listening,
and quite some who did or want to change away from Winno$ with their
existing, "old" PCs - are geared towards conditions of illimited means
(e.g., permanent/broadband net connection, units with huge mem and dito
HDs); which might well be a misconception.</besides>

// Heimo Claasen // <hammer at revobild dot net> // Brussels 2002-12-14
The WebPlace of ReRead - and much to read  ==>  http://www.revobild.net

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Re: RAM and swap partition

[Chuck Gelm]

Hi, Heimo:  

I am glad that you saw my 'tongue in cheek' humor.  ;-)


Heimo Claasen wrote:
> 
> Ok, ok, Chuck - sure "it depends" ;)
> (and oops, hwo do I use a swap _file_ instead of the "prescribed"
> partition ?)

# create and enable a 16 Megabyte swap file
dd if=/dev/zero of=/swap bs=1024 count=16384
mkswap /swap 16384
swapon /swap
#
# swapoff /swap


> >From your list, I conclude that it depends on all those six-and-a-half
> factors, even if I'm not soooo convinced what for instance, "distro
> AND version" 

 Some distributions automatically install large window managers
 Gnome|KDE and some small WMs, swafish|twm|fvwm2 and some console
 only.  Knowing the distribution might enlighten us about how much
 virtual RAM it would need.

>           (on top of the kernel number), the BogoMIPS or even the

 If a 100 bogoMIPS system ran two applications via 'at' or 'crond';
one at the hour and one at the half hour and each took 59 minutes
to run and each consumed 51% of available memory, then swap would
be needed.  If the bogoMIPS were doubled, each would finish 30
seconds before the other started and no swap would be needed.

> HD speed, would have to do with it.

 Uh, never mind about the HD speed. :-|

> And then I have this experience with one (notabene experimental) sound
> application which just doesn't care for how much swap there is - but
> it is a darn memhog in itself: it crashes if the data file (or too many
> together) loaded need too much _RAM_, regardless of how large I dimension
> the swap.
> So this real and practical example would tell me: no swap partition
> needed (EXACTLY for this one app.)
> 
> Another real-life case is with that not-so-brandnew laptop and its
> "small" HD of 2 GB and "poor" RAM (48 MB) installed, where Linux has
> to share space with a windoze and a small DOS partition. This runs
> vanilla apps in Linux - a GUI + a browser (including the connectivity
> gears) + a plug-in pic viewer at most, simultaneously. Here, seen HD
> space and RAM available (both hugely enormous, seen from my past-&-present
> DOS uses; all real work, including almost all net-work needed, is done
> in text mode and in the miniscule DOS compartment), the volume to set
> aside for a swap partition is even a "critical" decision.

 If you mount the DOS partitions, you could create swap files on
their unused HD space.

> Then there is one factor which you did not mention but which might be
> of decisive importance: if a unit is used by one person, it would most
> probably have just one user (and a very few "user accounts" only) and
> simultaneous use of different apps would be probably limited or rather,
> the user-"system-owner-administrator" could be enabled to establish a
> reasonable estimate of the real need for swap space on the perhaps
> not-so-enormously-new/big-HD -- _if_ s/he had some ways or indications
> for calculating it.
> 
> I think this is a reasonable demand, and I'm looking for some means to
> answer to this.  So, how would I measure how much swap this kernel or
> that application (in combination with what GUI, for instance) would
> need, in fact ?

 I have been wondering this also.  I often run 'top' and watch the 
top several lines of the 'top' display.  I need to understand more
about what each value means.  Actually, 'free' displays the same
information.  'top' is fancier to watch.  ;-)

 If I knew how to 'flush' all swap space,
I could 'flush', run some applications,
then see how much swap was used.

> > it may be suggested EXACTLY how much swap space you will need.
> 
> Hmm, for that laptop for instance, running yet a much too FAT Mandrake 8.2
> with kernel 2.4.18 (because Debian would not find the good video driver
> for the trickish LCD). I would gladly dish the mem-(and how much swap-?)
> hogging KDE and Nutsrape with it; though, regrettably, it must be able to
> run X and a SSL-capable net connection.

 I can run Netscape under fvwm95 and XFree86 v4.2.1 on my laptop
with 16 Megabytes of RAM, 32 Megabytes of swap, Slackware v8.0,
kernel 2.2.19.  So that much will squeeze into 48 Megabytes of
virtual RAM.  Perhaps XFree86 v4.2.0, 4.1.x, or 3.3.x would
consume less memory.  :-|

HTH, Chuck
> 
> I understood James' earlier questions quite similar to what I would ask
> for this example; and feel the are still not answered:
> > "if said user had less than X MB RAM, they will definitely need a swap
> > partition"? And what about guidelines for swap partition size in such a
> > case: can such be stated as well? Like, say, "if this individual has
> > only 32 MB RAM, he should have a 64 MB swap partition" or "if he has 64
> > MB RAM he'll only need a 64 MB swap partition"?
> 
> <besides>IMNSO too many of the posts especially on this list here -
> where I suppose are precisely quite a lot of "single-users" listening,
> and quite some who did or want to change away from Winno$ with their
> existing, "old" PCs - are geared towards conditions of illimited means
> (e.g., permanent/broadband net connection, units with huge mem and dito
> HDs); which might well be a misconception.</besides>
> 
> // Heimo Claasen // <hammer at revobild dot net> // Brussels 2002-12-14
> The WebPlace of ReRead - and much to read  ==>  http://www.revobild.net
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RE: RAM and swap partition

[Heimo Claasen]

It's still not really clear for my when and if, how much swap space is
needed.

There had been two opinions in this thread which clearly pointed to
none at all - surely qualified, one from own experience re
"workstations", the other (and that was the first time I heard about
this at all) that swap is (only?) needed when compiling and in order
to save a crash log.

The definition of "total (virtual) memory needed" for a/one programm
appears logical (and "natural"); but then, there should be some means
of measurement of precisely this, in order to do some reasonable -
and economic - decision on that workspace indeed needed.

Furthermore, it seems rational to approach this in function of the
actual use of (or installed) applications - i.e., to define, or even
to resize if necessary (when a memory hog is added), the swap partition
_after_ the otherwise complete installation of the "system".

// Heimo Claasen // <hammer at revobild dot net> // Brussels 2002-12-12
The WebPlace of ReRead - and much to read  ==>  http://www.revobild.net

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Re: RAM and swap partition

[Chuck Gelm]

Dear Heimo:

 If you will tell the list:
EXACTLY which distribution and version of linux and
EXACTLY which kernel and
EXACTLY which applications you will be using concurrently and
EXACTLY what your system's bogo MIPS is and
EXACTLY how fast your hard drive is and
EXACTLY how much RAM you have and
EXACTLY how much data your applications will be processing,
 it may be suggested EXACTLY how much swap space you will need.

 Until then, IMHO, the answer to this topic is,

 it depends.

 Tell us what you have and what you want to do with it,
and probably several fellows will suggest how much.
;-)

HTH, Chuck

Heimo Claasen wrote:
> 
> It's still not really clear for my when and if, how much swap space is
> needed.
> 
> There had been two opinions in this thread which clearly pointed to
> none at all - surely qualified, one from own experience re
> "workstations", the other (and that was the first time I heard about
> this at all) that swap is (only?) needed when compiling and in order
> to save a crash log.
> 
> The definition of "total (virtual) memory needed" for a/one programm
> appears logical (and "natural"); but then, there should be some means
> of measurement of precisely this, in order to do some reasonable -
> and economic - decision on that workspace indeed needed.
> 
> Furthermore, it seems rational to approach this in function of the
> actual use of (or installed) applications - i.e., to define, or even
> to resize if necessary (when a memory hog is added), the swap partition
> _after_ the otherwise complete installation of the "system".
> 
> // Heimo Claasen // <hammer at revobild dot net> // Brussels 2002-12-12
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RAM and swap partition

[Heimo Claasen]

As I'm increasing the RAM installed to the threefold of what there is
now, I wonder if I have to change/resize the swap partition.

(At present the swap is a small bit larger, 364 MB, than memory installed.
I sometimes read advice that the swap partitions should be _twice_ the
installed RAM; but I wonder why: wouldn't this be in function of how
many processes, and especially X-windows, are in use a a same time ?
As the single main memory hog to run on this machine is just one, 1,
application in one, again: 1, window, it dowsn't seem evident to waste
over 2 GB of HD space ?)

If resizing is adviseable: What's the best procdure ?

As it is, with this (Mdk-)install, there is quite a large, almost
empty partition devised as /home directory which would be the evident
candidate to get cut and parted, and I would prefer to not touch at all
on the other existing ones.  So I'd like best to define an all new
"swap" and likewise new "/home" from that (emptied) /home space, and
to redefine the old swap space of the HD as just some other data (or for
the "users" /homes) storage.

// Heimo Claasen // <hammer at revobild dot net> // Brussels 2002-12-07
The WebPlace of ReRead - and much to read  ==>  http://www.revobild.net

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Re: RAM and swap partition

[james niland]

The basic idea of the swap partition being double the
size of ram is that when your system has a crash it is
still capable of writing a core dump to the harddisk.
I think not many people really require that for a home
system or a system that is not critical.I know some
people who run happily without a swap at all. 
As long as you don't expect that your programs will
use more memory thant they used to before you upgraded
your memory and you don't run a critical system just
leave the swap at what it is. 
If you still want to change your swap partition, you
can make a new swap partition with eg fdisk and change
the entry for swap in /etc/fstab. 

James Niland





--- Heimo Claasen <hammer@revobild.net> wrote:
> As I'm increasing the RAM installed to the threefold
> of what there is
> now, I wonder if I have to change/resize the swap
> partition.
> 
> (At present the swap is a small bit larger, 364 MB,
> than memory installed.
> I sometimes read advice that the swap partitions
> should be _twice_ the
> installed RAM; but I wonder why: wouldn't this be in
> function of how
> many processes, and especially X-windows, are in use
> a a same time ?
> As the single main memory hog to run on this machine
> is just one, 1,
> application in one, again: 1, window, it dowsn't
> seem evident to waste
> over 2 GB of HD space ?)
> 
> If resizing is adviseable: What's the best procdure
> ?
> 
> As it is, with this (Mdk-)install, there is quite a
> large, almost
> empty partition devised as /home directory which
> would be the evident
> candidate to get cut and parted, and I would prefer
> to not touch at all
> on the other existing ones.  So I'd like best to
> define an all new
> "swap" and likewise new "/home" from that (emptied)
> /home space, and
> to redefine the old swap space of the HD as just
> some other data (or for
> the "users" /homes) storage.
> 
> // Heimo Claasen // <hammer at revobild dot net> //
> Brussels 2002-12-07
> The WebPlace of ReRead - and much to read  ==> 
> http://www.revobild.net
> 
> -
> To unsubscribe from this list: send the line
> "unsubscribe linux-newbie" in
> the body of a message to majordomo@vger.kernel.org
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> http://vger.kernel.org/majordomo-info.html
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RAM and swap partition

[Rolf Edlund]

Originally to: james niland


 jn> I know some people who run happily without a swap at all.

How low RAM can I use, without running a swap ? Can I for example do it on a 486 
with 4 MB RAM ?

... To quote or not to quote, that is the question.

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Re: RAM and swap partition

[Ray Olszewski]

At 01:15 PM 12/8/02 +0000, Rolf Edlund wrote:
>Originally to: james niland
>
>
>  jn> I know some people who run happily without a swap at all.
>
>How low RAM can I use, without running a swap ? Can I for example do it on 
>a 486
>with 4 MB RAM ?


The way you ask this question, it has no real answer. How little memory a 
system can run with depends on what tasks it is doing. And the choice of 
CPU is pretty much irrelevant to this question (its only slight relevance 
is in the smaller size of CPU-specific kernels).

That said ... running any sort of Linux system in less than 8 MB of real 
(not swap) RAM poses special challenges ... most modern distros can't even 
install on such systems (only Slackware, I think, still offers a "low 
memory" install option) and you won't be able to do much with such a 
system. In practice, the smallest systems I've ever run without swap were 
486s with 16 MB of RAM, and that was for special purpose systems like 
routers. While these days I routinely run my workstations without a swap 
partition, they have at least 256 MB of RAM.


--
-------------------------------------------"Never tell me the odds!"--------
Ray Olszewski					-- Han Solo
Palo Alto, California, USA			  ray@comarre.com
-------------------------------------------------------------------------------

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Re: RAM and swap partition

[Chuck Gelm]

Ditto to what Ray said.

 Perhaps you could run your system with a 'swap file' and see
how big it ever gets.  Then make a swap partition just that size
or a little larger.  ;-)

 My current firewall-router (aDSL to 100 Mb LAN) has 32 megabytes
  of RAM and has not used any swap memory, AFAICR.
 Another workstation with 64 M of RAM has used 3 M of swap.
 Another workstation with 160 M of RAM has used 2 M of swap.
 Another laptop with 16 M of RAM, XFfree86 v4.0.3, and I just
  ran Netscape v4.77 under fvwm95, loaded a small web page,
  has used 2.6 M of swap.

 IMHO, it depends.  ;-)

HTH, Chuck

Ray Olszewski wrote:
> 
> At 01:15 PM 12/8/02 +0000, Rolf Edlund wrote:
> >Originally to: james niland
> >
> >
> >  jn> I know some people who run happily without a swap at all.
> >
> >How low RAM can I use, without running a swap ? Can I for example
do it on
> >a 486
> >with 4 MB RAM ?
> 
> The way you ask this question, it has no real answer. How little
memory a
> system can run with depends on what tasks it is doing. And the
choice of
> CPU is pretty much irrelevant to this question (its only slight
relevance
> is in the smaller size of CPU-specific kernels).
> 
> That said ... running any sort of Linux system in less than 8 MB of
real
> (not swap) RAM poses special challenges ... most modern distros
can't even
> install on such systems (only Slackware, I think, still offers a
"low
> memory" install option) and you won't be able to do much with such
a
> system. In practice, the smallest systems I've ever run without
swap were
> 486s with 16 MB of RAM, and that was for special purpose systems
like
> routers. While these days I routinely run my workstations without a
swap
> partition, they have at least 256 MB of RAM.
> 
> --
> -------------------------------------------"Never tell me the
odds!"--------
> Ray Olszewski                                   -- Han Solo
> Palo Alto, California, USA                        ray@comarre.com
>
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>
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RAM and swap partition

[Rolf Edlund]

Originally to: Chuck Gelm


 CG>  IMHO, it depends.  ;-)

Looks like it. I have to test and see.. :)

... To quote or not to quote, that is the question.

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Re: RAM and swap partition

[ichi]

Ray Olszewski wrote:
> 
> (only Slackware, I think, still offers a "low memory" 
> install option) 

The latest Slackware (8.1) still provides a low-mem kernel.
However the standard installation scheme is too big to run
in 8mb RAM.  The instructions say 16mb RAM is required,
although 12mb is probably enough with the low-mem kernel.
For machines with less RAM than this, the instructions
recommend ZipSlack (which runs on a DOS filesystem).

There is, however, another option for computers with 
8mb RAM or less:
-------------------------------------------
http://www.volny.cz/basiclinux/slack81.html
-------------------------------------------
This uses a special low-RAM installation script that 
installs Slackware 8.1 to an ext2 partition.

Cheers,
Steven


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Re: RAM and swap partition

[whitnl73]

[-- Attachment #1: Type: TEXT/PLAIN, Size: 1035 bytes --]

On Mon, 9 Dec 2002 ichi@ihug.co.nz wrote:

> The latest Slackware (8.1) still provides a low-mem kernel.
> However the standard installation scheme is too big to run
> in 8mb RAM.  The instructions say 16mb RAM is required,
> although 12mb is probably enough with the low-mem kernel.
> For machines with less RAM than this, the instructions
> recommend ZipSlack (which runs on a DOS filesystem).
>
> There is, however, another option for computers with
> 8mb RAM or less:
> -------------------------------------------
> http://www.volny.cz/basiclinux/slack81.html
> -------------------------------------------
> This uses a special low-RAM installation script that
> installs Slackware 8.1 to an ext2 partition.
>
> Cheers,
> Steven
>
I don't have a script for it, but the attached micro-howto is based
on my experience putting slackware 7 onto an old 386 with 4mb, a little
100mb harddrive, a floppy, a serial port, and nothing else.  I used it
as an xterm when my monitor died.  X over a serial line is _slow_.

Lawson
--
---oops---

[-- Attachment #2: Type: TEXT/PLAIN, Size: 3850 bytes --]

lowmem-install micro-howto version 0.0.1 <lawson_whitney@juno.com>
19 February 2000    Use, distribute or change at your own risk.

/* To start with, this is based on slackware, because that is what I am
most familiar with, and it is easiest for me to work with and check to
make sure I have my facts right.  Other distro's differ in detail, but
the principles are the same. */

There is nothing magic or secret about installing a linux system.  Each
distro has its own way, but they all amount to the same thing:  to
install a linux system, boot up a tiny, self-contined linux system,
prepare the target medium (partition, make filesystems,..), mount it,
and (directed by a shell script) use standard linux tools to convert
and move files from the source to the target.

But hang on!  Linux will install onto all kinds of systems which may or
may not have all kinds of different storage media.  What do they have
in common, where the install filesystem can be rooted?  RAM!  And
indeed, all modern distro installs load the install fs to a ramdisk,
mount it on /, and take off running.  If you have a reasonably modern
system with 16mb or more, nothing could be easier.  With 12mb, you are
probably allright.  With 8mb you are just on the edge, and with 4 you
are SOL.  There just isn't room for 3822592 bytes of color.gz (that is
what color.gz from slackware 7 gunzips to) plus a kernel, plus buffers
in 4194304 bytes (less whatever the BIOS insists on using to shadow
itself with RAM, often at least 128k, perhaps as much as 412k).

No worry.  We just need to use a different device for / for the
install.  In the good old days before software got so fancy, an install
root filesystem would fit on a floppy.  Indeed, in slackware's
rootdsks/obsolete directory are some that will.  That is the simplest
way to run a low memory install:
just gzip -dc <your pet obsolete rootdisk>.gz >/dev/fd0
(If you don't have a linux system yet, in the install directory of the
distro are gzip.exe and rawrite.exe that can combine to do this with
windose)

and at the lilo prompt,

mount root=/dev/fd0

If you have some other medium to install from, a cd or a NIC or a zip
drive, you're away.  Using an obsolete install program doesn't render
the programs installed obsolete.  :-).  The install itself may not be
as slick or pretty, but if you cared about slick or pretty you wouldn't
be installing on to a machine with almost no RAM now, would you?

If you were planning to install from the floppy, don't give up hope. 
And if you wanted the newer, slicker color.gz, read on.

Go ahead and mount the obsolete root floppy.  We need it for a few
minutes.  We need another root device for the install.  If you still
have a [win]dose partition, you can use fips to shrink off 4mb to make
a new partition.  Or you can use fdisk to split off 4mb from the
partition you will install to, and mkfs -t ext2 (or mke2fs) to remake
the filesystem you wrecked by changing the partition size.  Get a block
device with about 4mb from somewhere.  I don't care where.  If you're
really strapped for space, 1440k will do, but we will have to use one
of the obsolete install roots again.

Now just install your install  root filesystem onto the new device.  If
you can get at the distro, say on a zip or cd drive, you can just

gzip -dc color.gz >/dev/<install root>
sync

If you can't, you can just use the root floppy we have been working
from:

cp /dev/fd0 /dev/<install root>
sync

if you don't like cp, use:
{dd|cat} </dev/fd0 >/dev/<install root>
sync

Now reboot:  shutdown -r now
switch back to the boot floppy.  At the LILO boot: prompt,

mount root=/dev/<install root>

Now you have a floppy drive free to install from, and enough memory for
the install programs to run from.

Have fun! 

RAM and swap partition

[Rolf Edlund]

Originally to: Ray Olszewski


 RO> While these days I routinely run my workstations without a swap
 RO> partition, they have at least 256 MB of RAM.

Ok.

... It's called Windows cuz they breake.

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Re: RAM and swap partition

[dashielljt]

The current wisdom is ram should be at most equal to memory installed and
nothing over.  Back in the early days of linux there was one system that
needed twice the ram but that's history and not valid for modern systems
and kernels.  In fact, that system was a BSD system not Linux.

Jude <dashielljt(at)gmpexpress-dot-net>

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Re: RAM and swap partition

[Heimo Claasen]

James - that's quite new to me:
> ... that when your system has a crash it is
> still capable of writing a core dump to the harddisk.

I understood it hitherto that it's needed for cases when a program needs
more mem than is free and available ?
Or asked the other way round - would any program which uses more RAM
than is available at a moment, be respeonsible care for "swapping" its
parts (or rather for instance, parts of its data) in/out by itself, and
to some own swap file ?

The second part of James' reply is precisely what I hoped for:
> (you) can make a new swap partition with eg fdisk and change
> the entry for swap in /etc/fstab.
Using an (emptied) partition to split off a part would be indeed much
less risky than a real resizeing of the swap _partition_; and much less
worksome, without GB-backups, <g>

-hc
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Re: RAM and swap partition

[whitnl73]

On 7 Dec 2002, Heimo Claasen wrote:

> James - that's quite new to me:
> > ... that when your system has a crash it is
> > still capable of writing a core dump to the harddisk.
>
> I understood it hitherto that it's needed for cases when a program needs
> more mem than is free and available ?
> Or asked the other way round - would any program which uses more RAM
> than is available at a moment, be respeonsible care for "swapping" its
> parts (or rather for instance, parts of its data) in/out by itself, and
> to some own swap file ?

For historical reasons, a pagefile is called a swap file.  It is virtual
memory.  The amount of memory available (to malloc(), FI) is the sum of
real memory and swap files, less some overhead for the page tables.  The
old swap is twice ram rule of thumb was for systems trying to run X with
4 or 8mb real memory.
>
> The second part of James' reply is precisely what I hoped for:
> > (you) can make a new swap partition with eg fdisk and change
> > the entry for swap in /etc/fstab.

Don't forget to mkswap.

> Using an (emptied) partition to split off a part would be indeed much
> less risky than a real resizeing of the swap _partition_; and much less
> worksome, without GB-backups, <g>
>
> -hc
>
Lawson
--
---oops---



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