[gentoo-user] 2GB of RAM

[gentoo-user] 2GB of RAM

[Ralph Slooten]

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Hi list,

Today I expended my RAM to 2GB (DDR) to my workstation, as apposed to
the initial 1GB I had. The RAm added is identical to the initial RAM.
Without changing the kernel (2.6.16.x) I still get 1GB available, and
digging into the kernel I found the section regarding the High Memory
Support and Memory split.

I did a bit of googeling, the first page I found (old) said to turn on
High Memory Support, however a more recent page
(http://linux-vserver.org/Step-by-Step+Guide+2.6) states to leave it off
and just change the split to 2/2 to make full use of 2GB of RAM.

I tried both ways, but either way I get poor 3D performance from UT2004
when I have this extra memory in.

Now I'm confused ;-) It's (kernel's) default is "3G/1G user/kernel
split" but there seems to be no documentation supplied with my kernel
(2.6.16.5).

Do any of you have experience with > 1GB of RAM, and efficiently getting
this to work _well_ on your systems? What ideal settings should I use in
my kernel? Are there any downsides to > 1GB?

With "3G/1G user/kernel split" selected, and "High Memory Support (off)"
I get 1GB despite 2GB in the motherboard, even when lilo boots with
append="mem=2048M". If I enable the 2/2 option instead I get 2G of RAM.
I tested the 2GB with 2x virtual machines (vmware) running each with
512MB ram (iE 1GB in use for vmware) and the system performed still
exceptionally well, however UT2004 still sucks when playing (sluggish
and screen jolts from time to time like I have too little RAM).

Any ideas?

Thanks,
Ralph

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Re: [gentoo-user] 2GB of RAM

[Steven Susbauer]

On Sun, 18 Jun 2006, Ralph Slooten wrote:

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>
> Hi list,
>
> Today I expended my RAM to 2GB (DDR) to my workstation, as apposed to
> the initial 1GB I had. The RAm added is identical to the initial RAM.
> Without changing the kernel (2.6.16.x) I still get 1GB available, and
> digging into the kernel I found the section regarding the High Memory
> Support and Memory split.
>
> I did a bit of googeling, the first page I found (old) said to turn on
> High Memory Support, however a more recent page
> (http://linux-vserver.org/Step-by-Step+Guide+2.6) states to leave it off
> and just change the split to 2/2 to make full use of 2GB of RAM.
>
> I tried both ways, but either way I get poor 3D performance from UT2004
> when I have this extra memory in.
>
> Now I'm confused ;-) It's (kernel's) default is "3G/1G user/kernel
> split" but there seems to be no documentation supplied with my kernel
> (2.6.16.5).
>
> Do any of you have experience with > 1GB of RAM, and efficiently getting
> this to work _well_ on your systems? What ideal settings should I use in
> my kernel? Are there any downsides to > 1GB?
>
> With "3G/1G user/kernel split" selected, and "High Memory Support (off)"
> I get 1GB despite 2GB in the motherboard, even when lilo boots with
> append="mem=2048M". If I enable the 2/2 option instead I get 2G of RAM.
> I tested the 2GB with 2x virtual machines (vmware) running each with
> 512MB ram (iE 1GB in use for vmware) and the system performed still
> exceptionally well, however UT2004 still sucks when playing (sluggish
> and screen jolts from time to time like I have too little RAM).
>
> Any ideas?
>
> Thanks,
> Ralph
>

What graphics card are you using? Sluggish and screen jolts sound possibly
like your graphics are too high for the card. Generally too little ram
will result in your HD doing a lot of work during gameplay.
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Re: [gentoo-user] 2GB of RAM

[Ralph Slooten]

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Steven Susbauer wrote:
> What graphics card are you using? Sluggish and screen jolts sound possibly
> like your graphics are too high for the card. Generally too little ram
> will result in your HD doing a lot of work during gameplay.

GeForce 6600/GeForce 6600 GT

No, with 1GB of RAM it worked just fine, but with 2GB of RAM it became
sluggish.

Greetings,
Ralph
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Re: [gentoo-user] 2GB of RAM

[David Klempner]

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* Ralph Slooten <axllent@gmail.com> [2006-06-18 12:52]:
> Today I expended my RAM to 2GB (DDR) to my workstation, as apposed to
> the initial 1GB I had. The RAm added is identical to the initial RAM.
> Without changing the kernel (2.6.16.x) I still get 1GB available, and
> digging into the kernel I found the section regarding the High Memory
> Support and Memory split.

Note that without doing *anything*, with a normal 3G/1G split, you'll
actually get 896M. Recent kernels added in a config option to have a
2.75G/1.25G split, which solves this problem; it makes sense to use that
if you have 1G of RAM.

> I did a bit of googeling, the first page I found (old) said to turn on
> High Memory Support, however a more recent page
> (http://linux-vserver.org/Step-by-Step+Guide+2.6) states to leave it off
> and just change the split to 2/2 to make full use of 2GB of RAM.

My understanding is that the performance hit from enabling high memory
support is actually fairly small; if you have more than 1G (where the
fix is unlikely to break anything) it's not worth worrying about.

> I tried both ways, but either way I get poor 3D performance from UT2004
> when I have this extra memory in.
> 
> (snip)
> 
> however UT2004 still sucks when playing (sluggish and screen jolts
> from time to time like I have too little RAM).
> 
> Any ideas?

My guesses is, as has already been suggested, that something is messed
up with your video driver. Did you recompile it when you recompile your
kernel? Is acceleration still working at all? Do you get the current
performance issues either without the extra RAM with a highmem kernel or
with the extra RAM without a highmem or 2G/2G kernel?

-- 
David Klempner

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Re: [gentoo-user] 2GB of RAM

[Ralph Slooten]

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Hi David,

David Klempner wrote:
 > Note that without doing *anything*, with a normal 3G/1G split, you'll
> actually get 896M. Recent kernels added in a config option to have a
> 2.75G/1.25G split, which solves this problem; it makes sense to use that
> if you have 1G of RAM.

This option must be really new because I don't have it. I have two 3/1
options, a 2/2 option and a 1/3 option. Either way, I'm now using 2GB.

> My understanding is that the performance hit from enabling high memory
> support is actually fairly small; if you have more than 1G (where the
> fix is unlikely to break anything) it's not worth worrying about.

> My guesses is, as has already been suggested, that something is messed
> up with your video driver. Did you recompile it when you recompile your
> kernel? Is acceleration still working at all? Do you get the current
> performance issues either without the extra RAM with a highmem kernel or
> with the extra RAM without a highmem or 2G/2G kernel?

Maybe this is the case, I'm not sure. For testing some other software I
upgraded to 2.16.6.16 2 weeks ago (when I still had 1GB) which resulted
in the same problem. I then went back to the previous-compiled 2.6.16.5
version which worked flawlessly. It is only now that I have actually
rebuilt the 2.6.16.5 kernel (due to RAM upgrade) and am having the same
problem. The NVidial kernel and glx (to be sure) were also rebuilt.

I did a bit of testing last night before I went to bed and it seems that
no matter what options I use in the kernel I'm getting bad performance
now from the graphics card. It still gets > 4000 fps with glxgears
though, so I'm not 100% sure it is the graphics card.

The question I was meaning to ask is what the ideal kernel settings
should be for 2GB of RAM... from there I'll look for other explanations
why the 3d isn't performing well.

Should I use 2/2 *and* highmem, or just 2/2 ? You suggest the highmem
does very little, but it's there for a valid reason I take it.

Thanks for the answers,
Ralph
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Re: [gentoo-user] 2GB of RAM

[David Klempner]

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* Ralph Slooten <axllent@gmail.com> [2006-06-19 00:25]:
> David Klempner wrote:
>  > Note that without doing *anything*, with a normal 3G/1G split, you'll
> > actually get 896M. Recent kernels added in a config option to have a
> > 2.75G/1.25G split, which solves this problem; it makes sense to use that
> > if you have 1G of RAM.
> 
> This option must be really new because I don't have it. I have two 3/1
> options, a 2/2 option and a 1/3 option. Either way, I'm now using 2GB.

It's one of the two "3/1" options; one of them is a PAGE_OFFSET of
0xC0000000 (3G) and the other is 0xB0000000 (2.75G); the latter is
suggested for someone using 1GB. (I was making that change myself by
hand until they added that option.)

In fact, the 2G option is slightly lower than 2G, which is why it works
with 2G of RAM.

> Maybe this is the case, I'm not sure. For testing some other software I
> upgraded to 2.16.6.16 2 weeks ago (when I still had 1GB) which resulted
> in the same problem. I then went back to the previous-compiled 2.6.16.5
> version which worked flawlessly. It is only now that I have actually
> rebuilt the 2.6.16.5 kernel (due to RAM upgrade) and am having the same
> problem. The NVidial kernel and glx (to be sure) were also rebuilt.
> 
> I did a bit of testing last night before I went to bed and it seems that
> no matter what options I use in the kernel I'm getting bad performance
> now from the graphics card. It still gets > 4000 fps with glxgears
> though, so I'm not 100% sure it is the graphics card.
> 
> The question I was meaning to ask is what the ideal kernel settings
> should be for 2GB of RAM... from there I'll look for other explanations
> why the 3d isn't performing well.

Do you have performance problems with any other applications? It
wouldn't surprise me too much if it's some random library issue that
specifically affects that game.

> Should I use 2/2 *and* highmem, or just 2/2 ? You suggest the highmem
> does very little, but it's there for a valid reason I take it.

If you're doing 2/2, then don't bother with highmem. Without highmem,
the kernel maps all of physical memory into its address space; this is
naive and fast, but it means that normal processes don't get use of that
space. This isn't a problem for most applications, but there are a few
that expect the extra address space to be available. A direct result of
the 2/2 split is that no single process can, even in theory, (directly)
use more than 2G of RAM, because it can't even *address* more than 2G.

This would be a more noticeable issue if you had 3G of RAM and did the
1/3 split; at that point, no process could use more than 1G. I've seen
long running processes (for example, firefox after a month with several
dozen open tabs) use more than that.

Highmem adds an extra layer of indirection to solve this problem; it's
slightly slower (but, I understand, the cost is minimal) but lets you
have your address space back while still being able to use all of your
RAM.

My suggestion is to use 3/1 with highmem. If you want, you could also
use 2/2 without highmem; it would probably be just slightly faster, but
could break stuff. Using 2/2 with highmem is (I think) pointless.

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Re: [gentoo-user] 2GB of RAM

[Ralph Slooten]

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Thanks David for the clear answers.... I'll investigate further. As for
the rest of the PC.... running great with extra RAM ~ it's just UT2004 I
have discovered to have an issue here.

The 2/2 is what I'm running with at the moment ... seems to be fine.

Thanks again,
Ralph

David Klempner wrote:
> * Ralph Slooten <axllent@gmail.com> [2006-06-19 00:25]:
>> David Klempner wrote:
>>  > Note that without doing *anything*, with a normal 3G/1G split, you'll
>>> actually get 896M. Recent kernels added in a config option to have a
>>> 2.75G/1.25G split, which solves this problem; it makes sense to use that
>>> if you have 1G of RAM.
>> This option must be really new because I don't have it. I have two 3/1
>> options, a 2/2 option and a 1/3 option. Either way, I'm now using 2GB.
> 
> It's one of the two "3/1" options; one of them is a PAGE_OFFSET of
> 0xC0000000 (3G) and the other is 0xB0000000 (2.75G); the latter is
> suggested for someone using 1GB. (I was making that change myself by
> hand until they added that option.)
> 
> In fact, the 2G option is slightly lower than 2G, which is why it works
> with 2G of RAM.
> 
>> Maybe this is the case, I'm not sure. For testing some other software I
>> upgraded to 2.16.6.16 2 weeks ago (when I still had 1GB) which resulted
>> in the same problem. I then went back to the previous-compiled 2.6.16.5
>> version which worked flawlessly. It is only now that I have actually
>> rebuilt the 2.6.16.5 kernel (due to RAM upgrade) and am having the same
>> problem. The NVidial kernel and glx (to be sure) were also rebuilt.
>>
>> I did a bit of testing last night before I went to bed and it seems that
>> no matter what options I use in the kernel I'm getting bad performance
>> now from the graphics card. It still gets > 4000 fps with glxgears
>> though, so I'm not 100% sure it is the graphics card.
>>
>> The question I was meaning to ask is what the ideal kernel settings
>> should be for 2GB of RAM... from there I'll look for other explanations
>> why the 3d isn't performing well.
> 
> Do you have performance problems with any other applications? It
> wouldn't surprise me too much if it's some random library issue that
> specifically affects that game.
> 
>> Should I use 2/2 *and* highmem, or just 2/2 ? You suggest the highmem
>> does very little, but it's there for a valid reason I take it.
> 
> If you're doing 2/2, then don't bother with highmem. Without highmem,
> the kernel maps all of physical memory into its address space; this is
> naive and fast, but it means that normal processes don't get use of that
> space. This isn't a problem for most applications, but there are a few
> that expect the extra address space to be available. A direct result of
> the 2/2 split is that no single process can, even in theory, (directly)
> use more than 2G of RAM, because it can't even *address* more than 2G.
> 
> This would be a more noticeable issue if you had 3G of RAM and did the
> 1/3 split; at that point, no process could use more than 1G. I've seen
> long running processes (for example, firefox after a month with several
> dozen open tabs) use more than that.
> 
> Highmem adds an extra layer of indirection to solve this problem; it's
> slightly slower (but, I understand, the cost is minimal) but lets you
> have your address space back while still being able to use all of your
> RAM.
> 
> My suggestion is to use 3/1 with highmem. If you want, you could also
> use 2/2 without highmem; it would probably be just slightly faster, but
> could break stuff. Using 2/2 with highmem is (I think) pointless.
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Re: [gentoo-user] 2GB of RAM

[Vladimir G. Ivanovic]

What are the names of the config options that change the memory split?
I'm running gentoo-sources-2.6.17, and for the life of me, I can't find
any config option that deal with memory (and I know they existed: I've
set them before.)

Thanks.

--- Vladimir

-- 
Vladimir G. Ivanovic <vgivanovic@comcast.net>
-- 
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Re: [gentoo-user] 2GB of RAM

[Justin R Findlay]

On Tue, Jun 20, 2006 at 09:01:26AM -0700, Vladimir G. Ivanovic wrote:
> What are the names of the config options that change the memory split?
> I'm running gentoo-sources-2.6.17, and for the life of me, I can't find
> any config option that deal with memory (and I know they existed: I've
> set them before.)

Are you running a 64 bit kernel?  I believe 64 bit architectures don't
have this memory limit so low.  I can't find it in my kernel config
either.


Justin
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Re: [gentoo-user] 2GB of RAM

[Mike Huber]

Yea, What architecture are you running on?  Is it possible that you
have some kind of memory interleaving option turned on in your bios
that isn't working right because of slight timing differences in the
manufacturing of each stick of ram?  Are they exactly the same spec
(CAS,NS, etc..)?  What's the processor?

On 6/20/06, Justin R Findlay <justin@jfindlay.us> wrote:
> On Tue, Jun 20, 2006 at 09:01:26AM -0700, Vladimir G. Ivanovic wrote:
> > What are the names of the config options that change the memory split?
> > I'm running gentoo-sources-2.6.17, and for the life of me, I can't find
> > any config option that deal with memory (and I know they existed: I've
> > set them before.)
>
> Are you running a 64 bit kernel?  I believe 64 bit architectures don't
> have this memory limit so low.  I can't find it in my kernel config
> either.
>
>
> Justin
> --
> gentoo-user@gentoo.org mailing list
>
>
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Re: [gentoo-user] 2GB of RAM

[Justin Piszcz]

# CONFIG_HIGHMEM64G is not set
CONFIG_VMSPLIT_3G=y
# CONFIG_VMSPLIT_3G_OPT is not set
# CONFIG_VMSPLIT_2G is not set
# CONFIG_VMSPLIT_1G is not set
CONFIG_PAGE_OFFSET=0xC0000000
CONFIG_HIGHMEM=y


On Tue, 20 Jun 2006, Vladimir G. Ivanovic wrote:

> What are the names of the config options that change the memory split?
> I'm running gentoo-sources-2.6.17, and for the life of me, I can't find
> any config option that deal with memory (and I know they existed: I've
> set them before.)
>
> Thanks.
>
> --- Vladimir
>
> -- 
> Vladimir G. Ivanovic <vgivanovic@comcast.net>
> -- 
> gentoo-user@gentoo.org mailing list
>
-- 
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Re: [gentoo-user] 2GB of RAM

[Graham Murray]

Justin Piszcz <jpiszcz@lucidpixels.com> writes:

> # CONFIG_HIGHMEM64G is not set
> CONFIG_VMSPLIT_3G=y
> # CONFIG_VMSPLIT_3G_OPT is not set
> # CONFIG_VMSPLIT_2G is not set
> # CONFIG_VMSPLIT_1G is not set
> CONFIG_PAGE_OFFSET=0xC0000000
> CONFIG_HIGHMEM=y

Is that with x86 and 2.6.17? I had those config options with 2.6.16,
but they are not present in 2.6.17. Though looking at
/usr/src/linux/arch/i386/Kconfig I cannot see why the option was not
offered.
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Re: [gentoo-user] 2GB of RAM

[David Klempner]

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* Graham Murray <graham@gmurray.org.uk> [2006-06-20 12:55]:
> Justin Piszcz <jpiszcz@lucidpixels.com> writes:
> 
> > # CONFIG_HIGHMEM64G is not set
> > CONFIG_VMSPLIT_3G=y
> > # CONFIG_VMSPLIT_3G_OPT is not set
> > # CONFIG_VMSPLIT_2G is not set
> > # CONFIG_VMSPLIT_1G is not set
> > CONFIG_PAGE_OFFSET=0xC0000000
> > CONFIG_HIGHMEM=y
> 
> Is that with x86 and 2.6.17? I had those config options with 2.6.16,
> but they are not present in 2.6.17. Though looking at
> /usr/src/linux/arch/i386/Kconfig I cannot see why the option was not
> offered.

For whatever reason, they made prompting about VMSPLIT dependent on
CONFIG_EMBEDDED.

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Re: [gentoo-user] 2GB of RAM

[Vladimir G. Ivanovic]

On Tue, 2006-06-20 at 14:05 -0500, David Klempner wrote:
> * Graham Murray <graham@gmurray.org.uk> [2006-06-20 12:55]:
> > Justin Piszcz <jpiszcz@lucidpixels.com> writes:
> > 
> > > # CONFIG_HIGHMEM64G is not set
> > > CONFIG_VMSPLIT_3G=y
> > > # CONFIG_VMSPLIT_3G_OPT is not set
> > > # CONFIG_VMSPLIT_2G is not set
> > > # CONFIG_VMSPLIT_1G is not set
> > > CONFIG_PAGE_OFFSET=0xC0000000
> > > CONFIG_HIGHMEM=y

I do not see *any* of these by grepping through .config.

        $ for string in highmem vmsplit page_offset; do 
        > fgrep -i $string /usr/src/linux-2.6.17-gentoo/.config
        > done
        $

Since I'm currently running a kernel & modules built (yesterday) with
this config, I'm pretty confident that the config is OK.

> > 
> > Is that with x86 and 2.6.17? I had those config options with 2.6.16,
> > but they are not present in 2.6.17. Though looking at
> > /usr/src/linux/arch/i386/Kconfig I cannot see why the option was not
> > offered.
> 
> For whatever reason, they made prompting about VMSPLIT dependent on
> CONFIG_EMBEDDED.

This does not seem to be the case on my system

        Linux scarlatti 2.6.17-gentoo #1 PREEMPT Mon Jun 19 15:28:07 PDT
        2006 x86_64 AMD Turion(tm) 64 Mobile Technology MT-32
        AuthenticAMD GNU/Linux.

All I get when I check CONFIG_EMBEDDED in gconfig is a bunch of
questions, which all default to yes, about using futexes, eventpoll,
etc. Nothing about memory.

Regardless, I'd expect to see those config options listed (but not set)
irrespective of whether CONFIG_EMBEDDED is or is not set.

The only thing I can conclude is that these configuration options have
been removed. (I checked the config resulting from 'make defconfig' as
well.) But that doesn't explain why I can't find them in older .configs.

        $ ls /usr/src/configs/*
         /usr/src/configs/2.6.14-archck7     /usr/src/configs/2.6.15-ck1
        /usr/src/configs/2.6.15-ck1-r1      /usr/src/configs/2.6.15-ck3-r1
        /usr/src/configs/2.6.15-gentoo-r4   /usr/src/configs/2.6.15-gentoo-r7
        /usr/src/configs/2.6.16-ck2         /usr/src/configs/2.6.16-gentoo-r1
        /usr/src/configs/2.6.16-gentoo-r10  /usr/src/configs/2.6.16-gentoo-r2
        /usr/src/configs/2.6.16-gentoo-r4   /usr/src/configs/2.6.16-gentoo-r6
        /usr/src/configs/2.6.16-gentoo-r8
        $ for string in highmem vmsplit page_offset; do  
        > fgrep -i $string /usr/src/configs/*
        > done
        $

I *know* I've seen them before (on my Fedora system?) I must be going
mad, or is this what Alzheimer's feels like?

--- Vladimir

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-- 
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Re: [gentoo-user] 2GB of RAM

[David Klempner]

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* Vladimir G. Ivanovic <vgivanovic@comcast.net> [2006-06-20 14:45]:
> > > 
> > > Is that with x86 and 2.6.17? I had those config options with 2.6.16,
> > > but they are not present in 2.6.17. Though looking at
> > > /usr/src/linux/arch/i386/Kconfig I cannot see why the option was not
> > > offered.
> > 
> > For whatever reason, they made prompting about VMSPLIT dependent on
> > CONFIG_EMBEDDED.
> 
> This does not seem to be the case on my system

It's still in the same place as it was before, and is *definitely* there
in both 2.6.17 and 2.6.17-gentoo. (the actual change occurred in rc4)

Processor type and features -> Memory split

Note that CONFIG_EMBEDDED is not in the same place.

General setup -> Configure standard kernel features

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Re: [gentoo-user] 2GB of RAM

[Vladimir G. Ivanovic]

On Tue, 2006-06-20 at 15:01 -0500, David Klempner wrote:
> * Vladimir G. Ivanovic <vgivanovic@comcast.net> [2006-06-20 14:45]:
> > > > 
> > > > Is that with x86 and 2.6.17? I had those config options with 2.6.16,
> > > > but they are not present in 2.6.17. Though looking at
> > > > /usr/src/linux/arch/i386/Kconfig I cannot see why the option was not
> > > > offered.
> > > 
> > > For whatever reason, they made prompting about VMSPLIT dependent on
> > > CONFIG_EMBEDDED.
> > 
> > This does not seem to be the case on my system
> 
> It's still in the same place as it was before, and is *definitely* there
> in both 2.6.17 and 2.6.17-gentoo. (the actual change occurred in rc4)
> 
> Processor type and features -> Memory split
> 
> Note that CONFIG_EMBEDDED is not in the same place.
> 
> General setup -> Configure standard kernel features

I figured it out. The VMSPLIT options are *not* available on 64-bit
systems. (Phew. It's neither encroaching madness nor Alzheimer's.)

--- Vladimir

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Vladimir G. Ivanovic <vgivanovic@comcast.net>
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Re: [gentoo-user] 2GB of RAM

[David Klempner]

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* Vladimir G. Ivanovic <vgivanovic@comcast.net> [2006-06-20 16:51]:
> I figured it out. The VMSPLIT options are *not* available on 64-bit
> systems. (Phew. It's neither encroaching madness nor Alzheimer's.)

Yeah... I suppose I wasn't paying close enough attention to what you
were saying. :-)

The VMSPLIT options are about how the kernel uses the 32 bit address
space (specifically, what fraction of the address space of each process
it reserves for its own use). A large portion of what a 64 bit system
gets you is more than 32 bits worth of address space, so I'm fairly sure
the entire issue is moot. :-)

(On the other hand, I have still yet to look really closely at the gory
details of how AMD64 works, and how linux uses it. I had a decent idea,
way back when the only implementations available were simulators, but
that was a while ago and I've forgotten a lot of it. As such, I might be
wrong.)

-- 
David Klempner

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Re: [gentoo-user] 2GB of RAM

[Vladimir G. Ivanovic]

On Wed, 2006-06-21 at 01:21 -0500, David Klempner wrote:
> * Vladimir G. Ivanovic <vgivanovic@comcast.net> [2006-06-20 16:51]:
> > I figured it out. The VMSPLIT options are *not* available on 64-bit
> > systems. (Phew. It's neither encroaching madness nor Alzheimer's.)
> 
> Yeah... I suppose I wasn't paying close enough attention to what you
> were saying. :-)

Well, it took way longer than I would have wished for me to catch on.
You'd think the total absence of any VMSPLIT options in *any* of my
saved config files would have been a sufficient hint, but no....

> 
> The VMSPLIT options are about how the kernel uses the 32 bit address
> space (specifically, what fraction of the address space of each process
> it reserves for its own use). A large portion of what a 64 bit system
> gets you is more than 32 bits worth of address space, so I'm fairly sure
> the entire issue is moot. :-)

You're most certainly right.

--- Vladimir

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Re: [gentoo-user] 2GB of RAM

[David Klempner]

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* David Klempner <klempner@imsanet.org> [2006-06-20 14:15]:
> For whatever reason, they made prompting about VMSPLIT dependent on
> CONFIG_EMBEDDED.

Quoting http://www.kernel.org/pub/linux/kernel/v2.6/ChangeLog-2.6.17 :

---

commit 9539d4e79fae8482bc64ced03a46c7c6d711d19e
Author: Andi Kleen <ak@suse.de>
Date:   Thu Apr 27 18:39:36 2006 -0700

    [PATCH] Mark VMSPLIT EMBEDDED
    
    Running abnormal VM splits causes weird problems - people can set non-standard
    splits by accident, then lots of time gets wasted diagnosing it - see the long
    "[stable] 2.6.16.6 breaks java...  sort of" email thread.
    
    So we need to make this option harder to set.  Use CONFIG_EMBEDDED for this.
    
    CONFIG_EMBEDDED isn't really the right thing to use, but there's nothing else
    obvious and avoiding these problems is more important than Kconfig purity.
    
    Signed-off-by: Andi Kleen <ak@suse.de>
    Cc: Adrian Bunk <bunk@stusta.de>
    Signed-off-by: Andrew Morton <akpm@osdl.org>
    Signed-off-by: Linus Torvalds <torvalds@osdl.org>

---

The reasoning here seems sound. It's probably not worth the trouble
(particularly for anything more severe than the 2.75/1.25 split for 1GB)
unless you actually know what you're doing.

-- 
David Klempner

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Re: [gentoo-user] 2GB of RAM

[Ralph Slooten]

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David Klempner wrote:
> For whatever reason, they made prompting about VMSPLIT dependent on
> CONFIG_EMBEDDED.

I upgraded yesterday to 2.6.17 and also noticed that there was no split
option. Not thinking much of it I installed the kernel which works fine,
except now /proc/kcore reports 897M, and `free` something to that effect
too.

So I take it I'm only using just less than 1/2 my RAM now, correct?

With 2GB of RAM, Do I now have to enable the embedded option (which
gives me a lot more options, most likely all of which I don't need), and
then select the 2/2 split, or .... ?

I noticed too that if I select the embedded option, but unselect all new
options that come with it I still get the memory split options. Is this
the right way to go?

It's a 64bit processor compiled and running on a 32bit system.

Greetings,
Ralph
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Re: [gentoo-user] 2GB of RAM

[David Klempner]

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* Ralph Slooten <axllent@gmail.com> [2006-06-21 00:15]:
> I upgraded yesterday to 2.6.17 and also noticed that there was no split
> option. Not thinking much of it I installed the kernel which works fine,
> except now /proc/kcore reports 897M, and `free` something to that effect
> too.
> 
> So I take it I'm only using just less than 1/2 my RAM now, correct?

Right.

> With 2GB of RAM, Do I now have to enable the embedded option (which
> gives me a lot more options, most likely all of which I don't need), and
> then select the 2/2 split, or .... ?

Actually, I side with the kernel developers on this; the fact that
they're hiding the VMSPLIT options is basically a subtle hint that they
don't want people using them who don't *really* know what they're doing.

I strongly suggest using CONFIG_HIGHMEM, and sticking with the default
3/1 split. (I mean, it's *slightly* slower, but on the other hand what
caused them to do this was random breaking of java that took a long time
to diagnose.) That said...

> I noticed too that if I select the embedded option, but unselect all new
> options that come with it I still get the memory split options. Is this
> the right way to go?

NO. As in, all of those options (with the exception of
CONFIG_KALLSYMS_EXTRA_PASS) default to yes, and all of those defaults
are very important. If you disable them, you will, for example, break
most of the kernel's logging (printk), lose the ability to get core
dumps, and lose futexes (which will break a lot of modern threading).
Basically, saying no to any option option on that page (with the
exception of the KALLSYMS stuff) *WILL* break your system.

So, make sure that everything, except CONFIG_KALLSYMS_EXTRA_PASS, on
that page is enabled. (that might be what you meant in the first place,
of course, but it's worth making sure...) All you need to be able to
select the VMSPLIT options is CONFIG_EMBEDDED (that is, saying yes to
the "Configure standard kernel features (for small systems)" item) which
doesn't actually have any impact on the code.

Hope this helps.

-- 
David Klempner

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Re: [gentoo-user] 2GB of RAM

[Ralph Slooten]

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Hi David,

David Klempner wrote:
> Actually, I side with the kernel developers on this; the fact that
> they're hiding the VMSPLIT options is basically a subtle hint that they
> don't want people using them who don't *really* know what they're doing.

Like me .. hence all the questions ;-) I just want to be able to use my
full RAM, as having 2GB and using < 1GB is just "uncool" ;-)

> I strongly suggest using CONFIG_HIGHMEM, and sticking with the default
> 3/1 split. (I mean, it's *slightly* slower, but on the other hand what
> caused them to do this was random breaking of java that took a long time
> to diagnose.) That said...

OK. I definitely will keep this in mind.

>> I noticed too that if I select the embedded option, but unselect all new
>> options that come with it I still get the memory split options. Is this
>> the right way to go?
> 
> NO. As in, all of those options (with the exception of
> CONFIG_KALLSYMS_EXTRA_PASS) default to yes, and all of those defaults
> are very important. If you disable them, you will, for example, break
> most of the kernel's logging (printk), lose the ability to get core
> dumps, and lose futexes (which will break a lot of modern threading).
> Basically, saying no to any option option on that page (with the
> exception of the KALLSYMS stuff) *WILL* break your system.
> 
> So, make sure that everything, except CONFIG_KALLSYMS_EXTRA_PASS, on
> that page is enabled. (that might be what you meant in the first place,
> of course, but it's worth making sure...) All you need to be able to
> select the VMSPLIT options is CONFIG_EMBEDDED (that is, saying yes to
> the "Configure standard kernel features (for small systems)" item) which
> doesn't actually have any impact on the code.

Sorry, but one thing remains unclear. Ignoring the fact that adding
embedded extras to your kernel on a non-embedded system just to get the
the VMSPLIT options is (in my opinion) confusing and unlogical, is this
step actually needed considering I (according to your advice) would take
the default VMSPLIT anyway?
What I mean is simply: If I enable HIGHMEM4GB to allow the kernel to use
my 2GB of RAM, do I still need to add the embedded options (as you
explain above), or is simply using HIGHMEM4GB enough? It's maybe a tough
question is ask, but you definitely seem to know exactly what you are
talking about ;-)

> Hope this helps.

Is sure does! Any advice to the above question? With that I should be
complete I think ;-) Where do you get your information from btw (I'm
curious as I didn't find much via Google explaining as clear as you did)?

Thanks again,
Ralph
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Re: [gentoo-user] 2GB of RAM

[David Klempner]

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* Ralph Slooten <axllent@gmail.com> [2006-06-21 04:12]:
> Sorry, but one thing remains unclear. Ignoring the fact that adding
> embedded extras to your kernel on a non-embedded system just to get the
> the VMSPLIT options is (in my opinion) confusing and unlogical, is this
> step actually needed considering I (according to your advice) would take
> the default VMSPLIT anyway?
> What I mean is simply: If I enable HIGHMEM4GB to allow the kernel to use
> my 2GB of RAM, do I still need to add the embedded options (as you
> explain above), or is simply using HIGHMEM4GB enough? It's maybe a tough
> question is ask, but you definitely seem to know exactly what you are
> talking about ;-)

Right; the right thing to do here is to not touch VMSPLIT at all, which
means there's no reason to be messing around with CONFIG_EMBEDDED. Just
set HIGHMEM4GB and be done with it (but, if you're editing a config
where you've already done so, make sure that you still have all of the
CONFIG_EMBEDDED dependent options set correctly before you unset it:
enable every one of the "standard kernel features" except for the extra
pass, and then make sure you have the default 3/1 VMSPLIT)

> > Hope this helps.
> 
> Is sure does! Any advice to the above question? With that I should be
> complete I think ;-) Where do you get your information from btw (I'm
> curious as I didn't find much via Google explaining as clear as you did)?

I did some googling about a year and a half ago, when I finally upgraded
my desktop from 512MB to 1GB and ran into these issues for the first
time, and I've spent some time poking around the kernel sources before.

-- 
David Klempner

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