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Old 06-19-2008, 10:59 AM
Bruno Wolff III
 
Default Memory, swap, and limits

On Wed, Jun 18, 2008 at 09:56:25 -0400,
James Kosin <jkosin@beta.intcomgrp.com> wrote:
>>
> Having TOO much swap space can be a detriment and not an asset.
> Usually, the rule of thumb I go by is allocate about 2x the amount of
> physical memory installed on the system; for machines with < 1M. This
> number will need to approach more or less 1x for machines with 1-2M.
> With machines with > 2M; I'm not sure swap space will make much of a
> difference, unless you rely on X heavily.

Presumably you mean Gigabytes above as there haven't been desktop machines
with memory on the order of 1 megabyte in about 15 years.

There are other factors in this. If you turn off overcommit you need to
have swap space available to back memory that may be allocated but not
really being used. So rules of thumb using ratios may not always be
applicable.

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Old 06-19-2008, 12:57 PM
James Kosin
 
Default Memory, swap, and limits

Bruno Wolff III wrote:

On Wed, Jun 18, 2008 at 09:56:25 -0400,
James Kosin <jkosin@beta.intcomgrp.com> wrote:



Having TOO much swap space can be a detriment and not an asset.
Usually, the rule of thumb I go by is allocate about 2x the amount of
physical memory installed on the system; for machines with < 1M. This
number will need to approach more or less 1x for machines with 1-2M.
With machines with > 2M; I'm not sure swap space will make much of a
difference, unless you rely on X heavily.



Presumably you mean Gigabytes above as there haven't been desktop machines
with memory on the order of 1 megabyte in about 15 years.

There are other factors in this. If you turn off overcommit you need to
have swap space available to back memory that may be allocated but not
really being used. So rules of thumb using ratios may not always be
applicable.



Sorry, I'm a bit dated and now I've probably revealed my age.
I've been around since the first personal computers and remember when
64K was considered a LOT of memory.


James

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Old 06-19-2008, 03:43 PM
Gene Heskett
 
Default Memory, swap, and limits

On Thursday 19 June 2008, James Kosin wrote:
[...]
>Sorry, I'm a bit dated and now I've probably revealed my age.
>I've been around since the first personal computers and remember when
>64K was considered a LOT of memory.
>
>James

So was I James, but heck, I remember Pearl Harbor, about when the transistor was
invented & I grew up with tubes. My first computer had a whopping 256 bytes of
ram! But we should let these youngsters muddle about and learn so they can be
kind to us in our dotage.

The universal thing I widely note, except on most of these lists, is that people
seem to think 'higher' education is a 16 year thing, when in reality school is
in session every day they manage wake up still breathing.

--
Cheers, Gene
"There are four boxes to be used in defense of liberty:
soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
The rose of yore is but a name, mere names are left to us.

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Old 06-19-2008, 03:50 PM
fred smith
 
Default Memory, swap, and limits

On Thu, Jun 19, 2008 at 08:57:18AM -0400, James Kosin wrote:
> Bruno Wolff III wrote:
> >On Wed, Jun 18, 2008 at 09:56:25 -0400,
> > James Kosin <jkosin@beta.intcomgrp.com> wrote:
> >
> >>>
> >>>
> >>Having TOO much swap space can be a detriment and not an asset.
> >>Usually, the rule of thumb I go by is allocate about 2x the amount of
> >>physical memory installed on the system; for machines with < 1M. This
> >>number will need to approach more or less 1x for machines with 1-2M.
> >>With machines with > 2M; I'm not sure swap space will make much of a
> >>difference, unless you rely on X heavily.
> >>
> >
> >Presumably you mean Gigabytes above as there haven't been desktop machines
> >with memory on the order of 1 megabyte in about 15 years.
> >
> >There are other factors in this. If you turn off overcommit you need to
> >have swap space available to back memory that may be allocated but not
> >really being used. So rules of thumb using ratios may not always be
> >applicable.
> >
> >
> Sorry, I'm a bit dated and now I've probably revealed my age.
> I've been around since the first personal computers and remember when
> 64K was considered a LOT of memory.

I remember when the company where I worked (my first programming job), which
sold a product based on a Dec lsi-11 board, decided that all new systems
would go out the door with 64KB--I thought we'd died and gone to heaven, all our
problems are over now! Of course it was only a few months before 64KB wasn't
big enough either.


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heaven, but only he who does the will of my Father who is in heaven."
------------------------------ Matthew 7:21 (niv) -----------------------------
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Old 06-19-2008, 03:59 PM
Bruno Wolff III
 
Default Memory, swap, and limits

On Wed, Jun 18, 2008 at 15:58:49 +0000,
Beartooth Sciurivore <beartooth@swva.net> wrote:
>
> OK; but then there's something else I don't know, or don't
> understand. Does a Fedora machine do any swapping while it has memory
> left? I didn't think I had (or needed) any control at all over swapping,
> beyond choosing how much space to afford it.

The vm.swappiness kernel parameter has an effect on swapping. I don't
remember the details, but it should be easy to find more information
if you are interested.

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Old 06-19-2008, 04:24 PM
tom
 
Default Memory, swap, and limits

On Thu, 19 Jun 2008, Gene Heskett wrote:


On Thursday 19 June 2008, James Kosin wrote:
[...]

Sorry, I'm a bit dated and now I've probably revealed my age.
I've been around since the first personal computers and remember when
64K was considered a LOT of memory.

James


So was I James, but heck, I remember Pearl Harbor, about when the transistor was
invented & I grew up with tubes. My first computer had a whopping 256 bytes of
ram! But we should let these youngsters muddle about and learn so they can be
kind to us in our dotage.

The universal thing I widely note, except on most of these lists, is that people
seem to think 'higher' education is a 16 year thing, when in reality school is
in session every day they manage wake up still breathing.


I shouldn't encourage off topic banter by participation, but I find I need
to publically agree with you. School is in session everyday you manage to
continue breathing. Sadly, many of us are so set in our ways and fictions
that we are pretty much asleep at school.


YMMV of course.

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Old 06-19-2008, 04:44 PM
Gene Heskett
 
Default Memory, swap, and limits

On Thursday 19 June 2008, tom wrote:

>Sadly, many of us are so set in our ways and fictions
>that we are pretty much asleep at school.

Sadly, I find that is a trap I have tripped over more than once of late, which
can be embarrassing in front of all these frogs.

--
Cheers, Gene
"There are four boxes to be used in defense of liberty:
soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
Cole's Law:
Thinly sliced cabbage.

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Old 06-21-2008, 02:16 PM
Bruno Wolff III
 
Default Memory, swap, and limits

On Wed, Jun 18, 2008 at 09:50:37 -0700,
Rick Stevens <ricks@nerd.com> wrote:
>
> If your RAM is heavily fragmented or heavily used, the system may find
> it difficult to locate adequate contiguous RAM and spend a lot of time
> swapping things to disk and back as tasks compete for the free RAM.

For most things the memory only needs to be contiguous in the virtual
address space. Real memory is allocated in pages and for most things
they don't need to be allocated contiguously.

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