Difference between revisions of "Swap on video ram"

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{{out of date}}
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{{accuracy}}
 
[[Category:Graphics]]
 
[[Category:Graphics]]
[[Category:Other hardware]]
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'''Warning:''' unless your X11 driver can be made to use less ram than exists (can be detected) your X server will tend to crash when you try to use the same section of RAM to store textures (even Qt does it) as swap. Using a video driver that allows you to override videoram should increase stability (vga and radeon (xf86-video-ati) do at least). Even then, you or I might have made mistakes and you can still get crashes or freezes (that do not listen to ctrl-alt-backspace; use the magic sysrq).
{{stub}}
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This is a work in progress
+
  
The fast memory on your graphics card (if you have one) can be used as general ram by using the MTD subsystem of the kernel. At the moment that part is not included in the stock arch kernel, so you have to build your own kernel, using [[ABS]] is probably the easiest way.
+
==Why Do it==
 +
The fast memory on your graphics card (if you have one) can be used as general ram (actually swap) by using the MTD subsystem of the kernel. If you have lots of videoram (256 MiB) this can increase system responsiveness (if you have around 256 MiB main ram too :).
 +
 
 +
Agp has slow reads; ~8 M/s. Making this less desirable.
  
 
==How To==
 
==How To==
 
===Kernel Stuff===
 
===Kernel Stuff===
you could rebuild the whole kernel like shown here. The modules can probabally be built separately though (perhaps with a pkgbuild)
+
MTD is now included in the kernel as of 2.6.23.1-6.
# Get the [[ABS]] tree
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# copy the /var/abs/kernels/kernel26 to /var/abs/local/kernel26-mtd, that will be your working directory
+
# change the name of the package to something else ie. from kernel26 to kernel26-mtd or something like that
+
# get and extract the sources with <pre>makepkg -o</pre>
+
# modify the configuration of the kernel, adding
+
## mtd_block (maybe mtd_char)
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## mtd_slram
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## mtd_phram (alternative and sucessor to slram)
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## mtd_ram probably too.
+
## other settings that go with those choices:
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<pre>CONFIG_MTD_MAP_BANK_WIDTH_1=y
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CONFIG_MTD_MAP_BANK_WIDTH_2=y
+
CONFIG_MTD_MAP_BANK_WIDTH_4=y
+
# CONFIG_MTD_MAP_BANK_WIDTH_8 is not set
+
# CONFIG_MTD_MAP_BANK_WIDTH_16 is not set
+
# CONFIG_MTD_MAP_BANK_WIDTH_32 is not set
+
CONFIG_MTD_CFI_I1=y
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CONFIG_MTD_CFI_I2=y</pre>
+
  
what the mtd section of my config ends up looking like (you could add this (almost?) anywhere in the config, just search for MTD, and replace the '#CONFIG_MTD= # is not set' with something else:
+
===Post-Kernel Stuff===
<pre>
+
When you are running a kernel with MTD modules, you have to load the modules specifying  the pci address ranges that correspond to the ram on your video card.
# Memory Technology Devices (MTD)
+
#
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CONFIG_MTD=m
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# CONFIG_MTD_DEBUG is not set
+
# CONFIG_MTD_CONCAT is not set
+
CONFIG_MTD_PARTITIONS=y
+
# CONFIG_MTD_REDBOOT_PARTS is not set
+
  
#
+
check the ranges with
# User Modules And Translation Layers
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lspci -vvv
#
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CONFIG_MTD_CHAR=m
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# CONFIG_MTD_BLKDEVS is not set
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CONFIG_MTD_BLOCK=m # is not set
+
# CONFIG_MTD_BLOCK_RO is not set
+
# CONFIG_FTL is not set
+
# CONFIG_NFTL is not set
+
# CONFIG_INFTL is not set
+
# CONFIG_RFD_FTL is not set
+
# CONFIG_SSFDC is not set
+
  
#
+
Then you look for the sections that name your video card as an example mine is here:
# RAM/ROM/Flash chip drivers
+
#
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# CONFIG_MTD_CFI is not set
+
# CONFIG_MTD_JEDECPROBE is not set
+
CONFIG_MTD_MAP_BANK_WIDTH_1=y
+
CONFIG_MTD_MAP_BANK_WIDTH_2=y
+
CONFIG_MTD_MAP_BANK_WIDTH_4=y
+
# CONFIG_MTD_MAP_BANK_WIDTH_8 is not set
+
# CONFIG_MTD_MAP_BANK_WIDTH_16 is not set
+
# CONFIG_MTD_MAP_BANK_WIDTH_32 is not set
+
CONFIG_MTD_CFI_I1=y
+
CONFIG_MTD_CFI_I2=y
+
# CONFIG_MTD_CFI_I4 is not set
+
# CONFIG_MTD_CFI_I8 is not set
+
CONFIG_MTD_RAM=m
+
# CONFIG_MTD_ROM is not set
+
# CONFIG_MTD_ABSENT is not set
+
# CONFIG_MTD_OBSOLETE_CHIPS is not set
+
  
#
 
# Mapping drivers for chip access
 
#
 
# CONFIG_MTD_COMPLEX_MAPPINGS is not set
 
# CONFIG_MTD_TS5500 is not set
 
CONFIG_MTD_PLATRAM=m
 
 
#
 
# Self-contained MTD device drivers
 
#
 
# CONFIG_MTD_PMC551 is not set
 
# CONFIG_MTD_DATAFLASH is not set
 
# CONFIG_MTD_M25P80 is not set
 
CONFIG_MTD_SLRAM=m
 
CONFIG_MTD_PHRAM=m
 
# CONFIG_MTD_MTDRAM is not set
 
# CONFIG_MTD_BLOCK2MTD is not set
 
 
#
 
# Disk-On-Chip Device Drivers
 
#
 
# CONFIG_MTD_DOC2000 is not set
 
# CONFIG_MTD_DOC2001 is not set
 
# CONFIG_MTD_DOC2001PLUS is not set
 
 
#
 
# NAND Flash Device Drivers
 
#
 
# CONFIG_MTD_NAND is not set
 
 
#
 
# OneNAND Flash Device Drivers
 
#
 
# CONFIG_MTD_ONENAND is not set
 
</pre>
 
===Post-Kernel Stuff===
 
When you are running the new kernel with those modules built you choose the pci address ranges where the device goes and then add something the following to your rc.local or similar:
 
 
<pre>
 
<pre>
# for using vram as swap
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01:00.0 VGA compatible controller: ATI Technologies Inc RV350 AR [Radeon 9600] (prog-if 00 [VGA controller])
modprobe slram map=VRAM,0xSTART RANGE HERE,+0xGOING THIS MUCH FARTHER
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modprobe mtdchar #probably unnecessary
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modprobe mtdblock
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mkswap /dev/mtdblock0
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swapon /dev/mtdblock0 -p 10 #higher priority gets used before disk
+
</pre>
+
you get the whole range you can take from lspci -vvv, looking for something that names your video card.
+
 
+
Learn hex aritmetic, or use a calculator (qalculate). You leave a certain space at the beginning of the address range, so that you graphics card can still function which is at least 4MiB if you decide to use the vga driver (at up to 1280x1024).
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====Example====
+
<pre>
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lspci -vvv
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01:00.0 VGA compatible controller: ATI Technologies Inc RV350 AR [Radeon 9600] (prog-if 00 [VGA])
+
 
Subsystem: PC Partner Limited Unknown device 0830
 
Subsystem: PC Partner Limited Unknown device 0830
Control: I/O+ Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR+ FastB2B-
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Control: I/O+ Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR+ FastB2B- DisINTx-
Status: Cap+ 66MHz+ UDF- FastB2B+ ParErr- DEVSEL=medium >TAbort- <TAbort- <MAbort- >SERR- <PERR-
+
Status: Cap+ 66MHz+ UDF- FastB2B+ ParErr- DEVSEL=medium >TAbort- <TAbort- <MAbort- >SERR- <PERR- INTx-
 
Latency: 64 (2000ns min), Cache Line Size: 32 bytes
 
Latency: 64 (2000ns min), Cache Line Size: 32 bytes
 
Interrupt: pin A routed to IRQ 11
 
Interrupt: pin A routed to IRQ 11
'' Region 0: Memory at e0000000 (32-bit, prefetchable) [size=256M]''
+
Region 0: Memory at e0000000 (32-bit, prefetchable) [size=256M]
 
Region 1: I/O ports at c800 [size=256]
 
Region 1: I/O ports at c800 [size=256]
 
Region 2: Memory at ff8f0000 (32-bit, non-prefetchable) [size=64K]
 
Region 2: Memory at ff8f0000 (32-bit, non-prefetchable) [size=64K]
 
Expansion ROM at ff8c0000 [disabled] [size=128K]
 
Expansion ROM at ff8c0000 [disabled] [size=128K]
Capabilities: [58] AGP version 2.0
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Capabilities: <access denied>
Status: RQ=80 Iso- ArqSz=0 Cal=0 SBA+ ITACoh- GART64- HTrans- 64bit- FW+ AGP3- Rate=x1,x2,x4
+
 
Command: RQ=32 ArqSz=0 Cal=0 SBA+ AGP+ GART64- 64bit- FW- Rate=x4
+
01:00.1 Display controller: ATI Technologies Inc RV350 AR [Radeon 9600] (Secondary)
Capabilities: [50] Power Management version 2
+
Subsystem: PC Partner Limited Unknown device 0831
Flags: PMEClk- DSI- D1+ D2+ AuxCurrent=0mA PME(D0-,D1-,D2-,D3hot-,D3cold-)
+
Control: I/O+ Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR- FastB2B- DisINTx-
Status: D0 PME-Enable- DSel=0 DScale=0 PME-
+
Status: Cap+ 66MHz+ UDF- FastB2B+ ParErr- DEVSEL=medium >TAbort- <TAbort- <MAbort- >SERR- <PERR- INTx-
 +
Latency: 64 (2000ns min), Cache Line Size: 32 bytes
 +
Region 0: Memory at d0000000 (32-bit, prefetchable) [size=256M]
 +
Region 1: Memory at ff8e0000 (32-bit, non-prefetchable) [size=64K]
 +
Capabilities: <access denied>
 
</pre>
 
</pre>
So here I have an address range starting at 0xe0000000, with a size of 256MiB, aka +0x10000000.
 
  
So choose how much space you can spare, maybe it is 16MiB which is 0x01000000.
+
What's important is Region 0, (the biggest one)
  
that space has to be at the start of the address range: add 0x01000000 to 0xe00000000 to get the start, subtract that from the end to make sure that you are using the whole space.
+
Since the video card needs some ram to serve its normal purpose, so you need to do some calculations. The offsets are easy to calculate as powers of 2. The card should use the beginning of the address range as framebuffer, textures etc. when limited (otherwise you get X11 crashing).
 +
 
 +
Example: total 2^28 bytes (256M) videoram, leaving 2^24 (32M) for the normal function (less will work fine)
 +
The start range, is 2^24 bytes more than the start of the pci address range shown by lspci -vvv.
 +
 
 +
The end is your total minus the amount you left for the card.
 +
 
 +
Load the modules in /etc/rc.conf
 +
MODULES=(otherModulesYouNeed '''slram mtdblock''')
 +
 
 +
In /etc/rc.local
 +
mkswap /dev/mtdblock0 && swapon /dev/mtdblock0 -p 10 #higher priority
 +
 
 +
Add this to /etc/modprobe.d/modprobe.conf
 +
options slram map=VRAM,0xStartRange,+0xUsedAmount
 +
 
 +
===Xorg Driver Config===
 +
To keep X stable, your video driver needs to be told to use less than the detected videoram. In the Device section of your /etc/X11/xorg.conf the declaration
 +
<pre>
 +
Section "Device"
 +
    Driver "radeon" # or whichever other driver you use
 +
    VideoRam 32768
 +
#other stuff
 +
EndSection
 +
</pre>
 +
specifies that you use 32 MiB of ram. Other drivers might take the number for videoram as being in MiB (I think vga does), check manpages.
 +
 
 +
==Checking the Swap space being used==
 +
The following command may help you getting the used swap in the different spaces like disk partitions, flash disks and possibly this example of the swap on video ram
 +
 
 +
<pre>
 +
swapon -s
 +
</pre>
  
 
==External Links==
 
==External Links==
[http://www.linux-mtd.infradead.org MTD website]
+
*[http://www.linux-mtd.infradead.org MTD website]
[http://gentoo-wiki.com/TIP_Use_memory_on_video_card_as_swap Gentoo Wiki]
+
*[http://en.gentoo-wiki.com/wiki/Using_Graphics_Card_Memory_as_Swap Gentoo Wiki]

Revision as of 12:06, 23 April 2012

Tango-view-refresh-red.pngThis article or section is out of date.Tango-view-refresh-red.png

Reason: please use the first argument of the template to provide a brief explanation. (Discuss in Talk:Swap on video ram#)

Tango-inaccurate.pngThe factual accuracy of this article or section is disputed.Tango-inaccurate.png

Reason: please use the first argument of the template to provide a brief explanation. (Discuss in Talk:Swap on video ram#)

Warning: unless your X11 driver can be made to use less ram than exists (can be detected) your X server will tend to crash when you try to use the same section of RAM to store textures (even Qt does it) as swap. Using a video driver that allows you to override videoram should increase stability (vga and radeon (xf86-video-ati) do at least). Even then, you or I might have made mistakes and you can still get crashes or freezes (that do not listen to ctrl-alt-backspace; use the magic sysrq).

Why Do it

The fast memory on your graphics card (if you have one) can be used as general ram (actually swap) by using the MTD subsystem of the kernel. If you have lots of videoram (256 MiB) this can increase system responsiveness (if you have around 256 MiB main ram too :).

Agp has slow reads; ~8 M/s. Making this less desirable.

How To

Kernel Stuff

MTD is now included in the kernel as of 2.6.23.1-6.

Post-Kernel Stuff

When you are running a kernel with MTD modules, you have to load the modules specifying the pci address ranges that correspond to the ram on your video card.

check the ranges with

lspci -vvv

Then you look for the sections that name your video card as an example mine is here:

01:00.0 VGA compatible controller: ATI Technologies Inc RV350 AR [Radeon 9600] (prog-if 00 [VGA controller])
	Subsystem: PC Partner Limited Unknown device 0830
	Control: I/O+ Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR+ FastB2B- DisINTx-
	Status: Cap+ 66MHz+ UDF- FastB2B+ ParErr- DEVSEL=medium >TAbort- <TAbort- <MAbort- >SERR- <PERR- INTx-
	Latency: 64 (2000ns min), Cache Line Size: 32 bytes
	Interrupt: pin A routed to IRQ 11
	Region 0: Memory at e0000000 (32-bit, prefetchable) [size=256M]
	Region 1: I/O ports at c800 [size=256]
	Region 2: Memory at ff8f0000 (32-bit, non-prefetchable) [size=64K]
	Expansion ROM at ff8c0000 [disabled] [size=128K]
	Capabilities: <access denied>

01:00.1 Display controller: ATI Technologies Inc RV350 AR [Radeon 9600] (Secondary)
	Subsystem: PC Partner Limited Unknown device 0831
	Control: I/O+ Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR- FastB2B- DisINTx-
	Status: Cap+ 66MHz+ UDF- FastB2B+ ParErr- DEVSEL=medium >TAbort- <TAbort- <MAbort- >SERR- <PERR- INTx-
	Latency: 64 (2000ns min), Cache Line Size: 32 bytes
	Region 0: Memory at d0000000 (32-bit, prefetchable) [size=256M]
	Region 1: Memory at ff8e0000 (32-bit, non-prefetchable) [size=64K]
	Capabilities: <access denied>

What's important is Region 0, (the biggest one)

Since the video card needs some ram to serve its normal purpose, so you need to do some calculations. The offsets are easy to calculate as powers of 2. The card should use the beginning of the address range as framebuffer, textures etc. when limited (otherwise you get X11 crashing).

Example: total 2^28 bytes (256M) videoram, leaving 2^24 (32M) for the normal function (less will work fine) The start range, is 2^24 bytes more than the start of the pci address range shown by lspci -vvv.

The end is your total minus the amount you left for the card.

Load the modules in /etc/rc.conf

MODULES=(otherModulesYouNeed slram mtdblock) 

In /etc/rc.local

mkswap /dev/mtdblock0 && swapon /dev/mtdblock0 -p 10 #higher priority

Add this to /etc/modprobe.d/modprobe.conf

options slram map=VRAM,0xStartRange,+0xUsedAmount

Xorg Driver Config

To keep X stable, your video driver needs to be told to use less than the detected videoram. In the Device section of your /etc/X11/xorg.conf the declaration

Section "Device"
    Driver "radeon" # or whichever other driver you use
    VideoRam 32768
	#other stuff
EndSection

specifies that you use 32 MiB of ram. Other drivers might take the number for videoram as being in MiB (I think vga does), check manpages.

Checking the Swap space being used

The following command may help you getting the used swap in the different spaces like disk partitions, flash disks and possibly this example of the swap on video ram

swapon -s 

External Links