Re: 4GB Physical. Less than 3GB in Linux.

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* Re: 4GB Physical. Less than 3GB in Linux.
       [not found] <fa.wZS4ieAkOMvNOj61QiUn9aS+YeM@ifi.uio.no>
@ 2007-04-16 14:33 ` Robert Hancock
  2007-04-16 14:52   ` Jeff Chua
  0 siblings, 1 reply; 10+ messages in thread
From: Robert Hancock @ 2007-04-16 14:33 UTC (permalink / raw)
  To: Jeff Chua; +Cc: lkml

Jeff Chua wrote:
> I've noticed that with 4GB physical ram, I'm only see 3098000 MB on
> the Dell 745, and 3107056MB on the IBM X60s.
> 
> I've tested with CONFIG_HIGHMEM4G=y, CONFIG_HIGHMEM64G=y,
> CONFIG_X86_PAE=y, but nothing makes any difference.

Chipset limitation. It uses up most of the MMIO region above 3GB 
preventing RAM from being mapped there, and doesn't support remapping 
the covered RAM to above 4GB. Nothing the kernel can do about it.

-- 
Robert Hancock      Saskatoon, SK, Canada
To email, remove "nospam" from hancockr@nospamshaw.ca
Home Page: http://www.roberthancock.com/


^ permalink raw reply	[flat|nested] 10+ messages in thread

* Re: 4GB Physical. Less than 3GB in Linux.
  2007-04-16 14:33 ` 4GB Physical. Less than 3GB in Linux Robert Hancock
@ 2007-04-16 14:52   ` Jeff Chua
  2007-04-16 19:56     ` Stefan Richter
  2007-04-17 18:26     ` Jasper Spaans
  0 siblings, 2 replies; 10+ messages in thread
From: Jeff Chua @ 2007-04-16 14:52 UTC (permalink / raw)
  To: Robert Hancock; +Cc: lkml

On 4/16/07, Robert Hancock <hancockr@shaw.ca> wrote:
> Jeff Chua wrote:
> > I've noticed that with 4GB physical ram, I'm only see 3098000 MB on
> > the Dell 745, and 3107056MB on the IBM X60s.
> >
> > I've tested with CONFIG_HIGHMEM4G=y, CONFIG_HIGHMEM64G=y,
> > CONFIG_X86_PAE=y, but nothing makes any difference.
>
> Chipset limitation. It uses up most of the MMIO region above 3GB
> preventing RAM from being mapped there, and doesn't support remapping
> the covered RAM to above 4GB. Nothing the kernel can do about it.

Well, I guess I learned the hard way. So it's better not to buy 4GB
... it turns out to be the same as buying one with just 3GB RAM.

Thanks,
Jeff.

^ permalink raw reply	[flat|nested] 10+ messages in thread

* Re: 4GB Physical. Less than 3GB in Linux.
  2007-04-16 14:52   ` Jeff Chua
@ 2007-04-16 19:56     ` Stefan Richter
  2007-04-17 18:26     ` Jasper Spaans
  1 sibling, 0 replies; 10+ messages in thread
From: Stefan Richter @ 2007-04-16 19:56 UTC (permalink / raw)
  To: Jeff Chua; +Cc: Robert Hancock, lkml

Jeff Chua wrote:
> On 4/16/07, Robert Hancock <hancockr@shaw.ca> wrote:
>> Chipset limitation. It uses up most of the MMIO region above 3GB
>> preventing RAM from being mapped there, and doesn't support remapping
>> the covered RAM to above 4GB. Nothing the kernel can do about it.
> 
> Well, I guess I learned the hard way. So it's better not to buy 4GB
> ... it turns out to be the same as buying one with just 3GB RAM.

Except for minimal performance differences if the 3GB configuration
doesn't support dual-channel mode.  (Not worth the price difference to 4GB.)
-- 
Stefan Richter
-=====-=-=== -=-- =----
http://arcgraph.de/sr/

^ permalink raw reply	[flat|nested] 10+ messages in thread

* Re: 4GB Physical. Less than 3GB in Linux.
  2007-04-16 14:52   ` Jeff Chua
  2007-04-16 19:56     ` Stefan Richter
@ 2007-04-17 18:26     ` Jasper Spaans
  2007-04-18  0:28       ` Jeff Chua
  1 sibling, 1 reply; 10+ messages in thread
From: Jasper Spaans @ 2007-04-17 18:26 UTC (permalink / raw)
  To: Jeff Chua; +Cc: lkml

On 4/16/07, Jeff Chua <jeff.chua.linux@gmail.com> wrote:
> On 4/16/07, Robert Hancock <hancockr@shaw.ca> wrote:
> > Jeff Chua wrote:
> > > I've noticed that with 4GB physical ram, I'm only see 3098000 MB on
> > > the Dell 745, and 3107056MB on the IBM X60s.
> > >
> > > I've tested with CONFIG_HIGHMEM4G=y, CONFIG_HIGHMEM64G=y,
> > > CONFIG_X86_PAE=y, but nothing makes any difference.
> >
> > Chipset limitation. It uses up most of the MMIO region above 3GB
> > preventing RAM from being mapped there, and doesn't support remapping
> > the covered RAM to above 4GB. Nothing the kernel can do about it.
>
> Well, I guess I learned the hard way. So it's better not to buy 4GB
> ... it turns out to be the same as buying one with just 3GB RAM.

Might be a setting in the bios... look for something like memory hole,
memory remapping, 4G DRAM, etc.

VrGr,
-- 
Jasper Spaans                                       http://jsp.vs19.net/

               This line was last modified 0 seconds ago.

^ permalink raw reply	[flat|nested] 10+ messages in thread

* Re: 4GB Physical. Less than 3GB in Linux.
  2007-04-17 18:26     ` Jasper Spaans
@ 2007-04-18  0:28       ` Jeff Chua
  0 siblings, 0 replies; 10+ messages in thread
From: Jeff Chua @ 2007-04-18  0:28 UTC (permalink / raw)
  To: Jasper Spaans; +Cc: lkml

On 4/18/07, Jasper Spaans <jasper@vs19.net> wrote:

> Might be a setting in the bios... look for something like memory hole,
> memory remapping, 4G DRAM, etc.

I checked. BIOS says 4GB. No memory hole setting. But I'll play around
a bit more.

Thanks,
Jeff.

^ permalink raw reply	[flat|nested] 10+ messages in thread

* 4GB Physical. Less than 3GB in Linux.
@ 2007-04-16  7:28 Jeff Chua
  2007-04-16 13:12 ` Fortier,Vincent [Montreal]
  2007-04-16 14:17 ` Stefan Richter
  0 siblings, 2 replies; 10+ messages in thread
From: Jeff Chua @ 2007-04-16  7:28 UTC (permalink / raw)
  To: lkml

I've noticed that with 4GB physical ram, I'm only see 3098000 MB on
the Dell 745, and 3107056MB on the IBM X60s.

I've tested with CONFIG_HIGHMEM4G=y, CONFIG_HIGHMEM64G=y,
CONFIG_X86_PAE=y, but nothing makes any difference.

Tested on Linux 2.6.20, Linux 2.6.21-rc7.

# dmesg
copy_e820_map() start: 0000000000000000 size: 000000000009f000 end:
000000000009f000 type: 1
copy_e820_map() type is E820_RAM
copy_e820_map() start: 000000000009f000 size: 0000000000001000 end:
00000000000a0000 type: 2
copy_e820_map() start: 00000000000dc000 size: 0000000000024000 end:
0000000000100000 type: 2
copy_e820_map() start: 0000000000100000 size: 00000000bf5d0000 end:
00000000bf6d0000 type: 1
copy_e820_map() type is E820_RAM
copy_e820_map() start: 00000000bf6d0000 size: 000000000000f000 end:
00000000bf6df000 type: 3
copy_e820_map() start: 00000000bf6df000 size: 0000000000021000 end:
00000000bf700000 type: 4
copy_e820_map() start: 00000000bf700000 size: 0000000000900000 end:
00000000c0000000 type: 2
copy_e820_map() start: 00000000f0000000 size: 0000000004000000 end:
00000000f4000000 type: 2
copy_e820_map() start: 00000000fec00000 size: 0000000000010000 end:
00000000fec10000 type: 2
copy_e820_map() start: 00000000fed00000 size: 0000000000000400 end:
00000000fed00400 type: 2
copy_e820_map() start: 00000000fed14000 size: 0000000000006000 end:
00000000fed1a000 type: 2
copy_e820_map() start: 00000000fed1c000 size: 0000000000074000 end:
00000000fed90000 type: 2
copy_e820_map() start: 00000000fee00000 size: 0000000000001000 end:
00000000fee01000 type: 2
copy_e820_map() start: 00000000ff800000 size: 0000000000800000 end:
0000000100000000 type: 2
 BIOS-e820: 0000000000000000 - 000000000009f000 (usable)
 BIOS-e820: 000000000009f000 - 00000000000a0000 (reserved)
 BIOS-e820: 00000000000dc000 - 0000000000100000 (reserved)
 BIOS-e820: 0000000000100000 - 00000000bf6d0000 (usable)
 BIOS-e820: 00000000bf6d0000 - 00000000bf6df000 (ACPI data)
 BIOS-e820: 00000000bf6df000 - 00000000bf700000 (ACPI NVS)
 BIOS-e820: 00000000bf700000 - 00000000c0000000 (reserved)
 BIOS-e820: 00000000f0000000 - 00000000f4000000 (reserved)
 BIOS-e820: 00000000fec00000 - 00000000fec10000 (reserved)
 BIOS-e820: 00000000fed00000 - 00000000fed00400 (reserved)
 BIOS-e820: 00000000fed14000 - 00000000fed1a000 (reserved)
 BIOS-e820: 00000000fed1c000 - 00000000fed90000 (reserved)
 BIOS-e820: 00000000fee00000 - 00000000fee01000 (reserved)
 BIOS-e820: 00000000ff800000 - 0000000100000000 (reserved)
2166MB HIGHMEM available.
896MB LOWMEM available.

Memory: 3106140k/3136320k available (2225k kernel code, 29072k
reserved, 910k data, 196k init, 2218816k highmem)
virtual kernel memory layout:
    fixmap  : 0xfff50000 - 0xfffff000   ( 700 kB)
    pkmap   : 0xff800000 - 0xffc00000   (4096 kB)
    vmalloc : 0xf8800000 - 0xff7fe000   ( 111 MB)
    lowmem  : 0xc0000000 - 0xf8000000   ( 896 MB)
      .init : 0xc0416000 - 0xc0447000   ( 196 kB)
      .data : 0xc032c513 - 0xc040ff34   ( 910 kB)
      .text : 0xc0100000 - 0xc032c513   (2225 kB)


Thanks,
Jeff.

^ permalink raw reply	[flat|nested] 10+ messages in thread

* RE: 4GB Physical. Less than 3GB in Linux.
  2007-04-16  7:28 Jeff Chua
@ 2007-04-16 13:12 ` Fortier,Vincent [Montreal]
  2007-04-16 14:17 ` Stefan Richter
  1 sibling, 0 replies; 10+ messages in thread
From: Fortier,Vincent [Montreal] @ 2007-04-16 13:12 UTC (permalink / raw)
  To: Jeff Chua, lkml

> 
> I've noticed that with 4GB physical ram, I'm only see 3098000 
> MB on the Dell 745, and 3107056MB on the IBM X60s.
> 
> I've tested with CONFIG_HIGHMEM4G=y, CONFIG_HIGHMEM64G=y, 
> CONFIG_X86_PAE=y, but nothing makes any difference.
> 
> Tested on Linux 2.6.20, Linux 2.6.21-rc7.

Got similar problem on a HP XW6200:
http://bugzilla.kernel.org/show_bug.cgi?id=7111

Tought I was the only one getting this!

> # dmesg
> copy_e820_map() start: 0000000000000000 size: 000000000009f000 end:
> 000000000009f000 type: 1
> copy_e820_map() type is E820_RAM
> copy_e820_map() start: 000000000009f000 size: 0000000000001000 end:
> 00000000000a0000 type: 2
> copy_e820_map() start: 00000000000dc000 size: 0000000000024000 end:
> 0000000000100000 type: 2
> copy_e820_map() start: 0000000000100000 size: 00000000bf5d0000 end:
> 00000000bf6d0000 type: 1
> copy_e820_map() type is E820_RAM
> copy_e820_map() start: 00000000bf6d0000 size: 000000000000f000 end:
> 00000000bf6df000 type: 3
> copy_e820_map() start: 00000000bf6df000 size: 0000000000021000 end:
> 00000000bf700000 type: 4
> copy_e820_map() start: 00000000bf700000 size: 0000000000900000 end:
> 00000000c0000000 type: 2
> copy_e820_map() start: 00000000f0000000 size: 0000000004000000 end:
> 00000000f4000000 type: 2
> copy_e820_map() start: 00000000fec00000 size: 0000000000010000 end:
> 00000000fec10000 type: 2
> copy_e820_map() start: 00000000fed00000 size: 0000000000000400 end:
> 00000000fed00400 type: 2
> copy_e820_map() start: 00000000fed14000 size: 0000000000006000 end:
> 00000000fed1a000 type: 2
> copy_e820_map() start: 00000000fed1c000 size: 0000000000074000 end:
> 00000000fed90000 type: 2
> copy_e820_map() start: 00000000fee00000 size: 0000000000001000 end:
> 00000000fee01000 type: 2
> copy_e820_map() start: 00000000ff800000 size: 0000000000800000 end:
> 0000000100000000 type: 2
>  BIOS-e820: 0000000000000000 - 000000000009f000 (usable)
>  BIOS-e820: 000000000009f000 - 00000000000a0000 (reserved)
>  BIOS-e820: 00000000000dc000 - 0000000000100000 (reserved)
>  BIOS-e820: 0000000000100000 - 00000000bf6d0000 (usable)
>  BIOS-e820: 00000000bf6d0000 - 00000000bf6df000 (ACPI data)
>  BIOS-e820: 00000000bf6df000 - 00000000bf700000 (ACPI NVS)
>  BIOS-e820: 00000000bf700000 - 00000000c0000000 (reserved)
>  BIOS-e820: 00000000f0000000 - 00000000f4000000 (reserved)
>  BIOS-e820: 00000000fec00000 - 00000000fec10000 (reserved)
>  BIOS-e820: 00000000fed00000 - 00000000fed00400 (reserved)
>  BIOS-e820: 00000000fed14000 - 00000000fed1a000 (reserved)
>  BIOS-e820: 00000000fed1c000 - 00000000fed90000 (reserved)
>  BIOS-e820: 00000000fee00000 - 00000000fee01000 (reserved)
>  BIOS-e820: 00000000ff800000 - 0000000100000000 (reserved) 
> 2166MB HIGHMEM available.
> 896MB LOWMEM available.
> 
> Memory: 3106140k/3136320k available (2225k kernel code, 
> 29072k reserved, 910k data, 196k init, 2218816k highmem) 
> virtual kernel memory layout:
>     fixmap  : 0xfff50000 - 0xfffff000   ( 700 kB)
>     pkmap   : 0xff800000 - 0xffc00000   (4096 kB)
>     vmalloc : 0xf8800000 - 0xff7fe000   ( 111 MB)
>     lowmem  : 0xc0000000 - 0xf8000000   ( 896 MB)
>       .init : 0xc0416000 - 0xc0447000   ( 196 kB)
>       .data : 0xc032c513 - 0xc040ff34   ( 910 kB)
>       .text : 0xc0100000 - 0xc032c513   (2225 kB)
> 
> 
> Thanks,
> Jeff.

- vin

^ permalink raw reply	[flat|nested] 10+ messages in thread

* Re: 4GB Physical. Less than 3GB in Linux.
  2007-04-16  7:28 Jeff Chua
  2007-04-16 13:12 ` Fortier,Vincent [Montreal]
@ 2007-04-16 14:17 ` Stefan Richter
  2007-04-16 14:47   ` Jeff Chua
  1 sibling, 1 reply; 10+ messages in thread
From: Stefan Richter @ 2007-04-16 14:17 UTC (permalink / raw)
  To: Jeff Chua; +Cc: linux-kernel

Jeff Chua wrote:
> I've noticed that with 4GB physical ram, I'm only see 3098000 MB on
> the Dell 745, and 3107056MB on the IBM X60s.
> 
> I've tested with CONFIG_HIGHMEM4G=y, CONFIG_HIGHMEM64G=y,
> CONFIG_X86_PAE=y, but nothing makes any difference.
> 
> Tested on Linux 2.6.20, Linux 2.6.21-rc7.

The X60 most certainly contains a chipset which severely limits the
amount of accessible RAM due to issues with remapping of PCIe addresses.
 Intel explains it somewhere on their web presence.  A quick & lazy web
search turned this Intel paper up:
http://www.polywell.com/us/support/faq/4GB_Rev1.pdf
-- 
Stefan Richter
-=====-=-=== -=-- -==-=
http://arcgraph.de/sr/

^ permalink raw reply	[flat|nested] 10+ messages in thread

* Re: 4GB Physical. Less than 3GB in Linux.
  2007-04-16 14:17 ` Stefan Richter
@ 2007-04-16 14:47   ` Jeff Chua
  2007-04-16 18:25     ` Stefan Richter
  0 siblings, 1 reply; 10+ messages in thread
From: Jeff Chua @ 2007-04-16 14:47 UTC (permalink / raw)
  To: Stefan Richter; +Cc: linux-kernel, Fortier,Vincent [Montreal]

On 4/16/07, Stefan Richter <stefanr@s5r6.in-berlin.de> wrote:
> The X60 most certainly contains a chipset which severely limits the
> amount of accessible RAM due to issues with remapping of PCIe addresses.
>  Intel explains it somewhere on their web presence.  A quick & lazy web
> search turned this Intel paper up:
> http://www.polywell.com/us/support/faq/4GB_Rev1.pdf

Stefan,

That's interesting.Thanks for the pointer. I wondered if there's
anyone working on a patch for this.

I've seen this problem before, just like Vincent, I thought it's only
me. Didn't really bother me, until I got a new X60s with 4GB RAM.

Thanks,
Jeff.

^ permalink raw reply	[flat|nested] 10+ messages in thread

* Re: 4GB Physical. Less than 3GB in Linux.
  2007-04-16 14:47   ` Jeff Chua
@ 2007-04-16 18:25     ` Stefan Richter
  0 siblings, 0 replies; 10+ messages in thread
From: Stefan Richter @ 2007-04-16 18:25 UTC (permalink / raw)
  To: Jeff Chua; +Cc: linux-kernel, Fortier,Vincent [Montreal]

Jeff Chua wrote:
> On 4/16/07, Stefan Richter <stefanr@s5r6.in-berlin.de> wrote:
>> The X60 most certainly contains a chipset which severely limits the
>> amount of accessible RAM due to issues with remapping of PCIe addresses.
...
> I wondered if there's anyone working on a patch for this.

All I heard of is that the successor chipsets are supposed to lessen or
eliminate the problem.
-- 
Stefan Richter
-=====-=-=== -=-- =----
http://arcgraph.de/sr/

^ permalink raw reply	[flat|nested] 10+ messages in thread

end of thread, other threads:[~2007-04-18  0:28 UTC | newest]

Thread overview: 10+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
     [not found] <fa.wZS4ieAkOMvNOj61QiUn9aS+YeM@ifi.uio.no>
2007-04-16 14:33 ` 4GB Physical. Less than 3GB in Linux Robert Hancock
2007-04-16 14:52   ` Jeff Chua
2007-04-16 19:56     ` Stefan Richter
2007-04-17 18:26     ` Jasper Spaans
2007-04-18  0:28       ` Jeff Chua
2007-04-16  7:28 Jeff Chua
2007-04-16 13:12 ` Fortier,Vincent [Montreal]
2007-04-16 14:17 ` Stefan Richter
2007-04-16 14:47   ` Jeff Chua
2007-04-16 18:25     ` Stefan Richter

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