Difference between revisions of "Swap on video ram"

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[[Category:Graphics]]
 
[[Category:Graphics]]
[[Category:Other hardware]]
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{{Expansion|This article may need to be expanded or revised for contemporary hardware.}}
{{stub}}
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{{Out of date|Graphics hardware referenced is quite old at this point. rconf is referenced instead of systemd. This article primarily references a now archived article from Gentoo's wiki.}}
This is a work in progress: the stuff in here is not tested that much, and it is possible that you will run out of video ram/have a conflict and your xserver will crash.
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{{Related articles start}}
 +
{{Related|Maximizing performance}}
 +
{{Related articles end}}
 +
A short article on utilizing video memory for system swap.
  
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.
+
{{Warning|This will not work with binary drivers.}}
 +
{{Warning|Unless your graphics driver can be made to use less ram than is detected, Xorg may crash when you try to use the same section of RAM to store textures as swap. Using a video driver that allows you to override videoram should increase stability.}}
  
==How To==
+
==Potential benefits==
===Kernel Stuff===
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A graphics card with GDDR SDRAM or DDR SDRAM may be used as swap by using the MTD subsystem of the kernel. Systems with dedicated graphics memory of 256 MB or greater which also have limited amounts of system memory (DDR SDRAM) may benefit the most from this type of setup.
Get a kernel version >= 2.6.23.1-6
+
 
===Post-Kernel Stuff===
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{{Warning|The accelerated graphics bus (AGP) is a legacy bus and has a limited amount of bus bandwidth. This may limit reads to approximately 8 MB per second.}}
 +
 
 +
==Kernel requirements==
 +
MTD is in the mainline kernel since version 2.6.23.
 +
 
 +
==Pre-setup==
 
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.
 
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
+
To find the available memory ranges run the following command and look for the VGA compatible controller section (see the example below).
<pre>lspci -vvv</pre>
+
 
 +
{{hc|$ lspci -vvv|<nowiki>
 +
01:00.0 VGA compatible controller: NVIDIA Corporation GK104 [GeForce GTX 670] (rev a1) (prog-if 00 [VGA controller])
 +
Subsystem: ASUSTeK Computer Inc. Device 8405
 +
Control: I/O+ Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR- FastB2B- DisINTx-
 +
Status: Cap+ 66MHz- UDF- FastB2B- ParErr- DEVSEL=fast >TAbort- <TAbort- <MAbort- >SERR- <PERR- INTx-
 +
Latency: 0
 +
Interrupt: pin A routed to IRQ 57
 +
Region 0: Memory at f5000000 (32-bit, non-prefetchable) [size=16M]
 +
Region 1: Memory at e8000000 (64-bit, prefetchable) [size=128M]
 +
Region 3: Memory at f0000000 (64-bit, prefetchable) [size=32M]
 +
Region 5: I/O ports at e000 [size=128]
 +
[virtual] Expansion ROM at f6000000 [disabled] [size=512K]
 +
Capabilities: <access denied>
 +
Kernel driver in use: nvidia
 +
Kernel modules: nouveau, nvidia</nowiki>}}
 +
 
 +
{{Note|Systems with multiple GPUs will likely have multiple entries here.}}
 +
 
 +
Of most potential benefit is a region that is prefectable, 64-bit, and the largest in size.
 +
{{Note|The graphics card used above has 2 GB of GDDR5 SDRAM, though as indicated above the full amount is not exposed or listed by the command provided above.}}
 +
 
 +
A video card needs some of its memory to function, as such some calculations are needed. The offsets are easy to calculate as powers of 2. The card should use the beginning of the address range as a framebuffer for textures and such. However, if limited or as indicated in the beginning of this article, if two programs try to write to the same sectors, stability issues are likely to occur.
 +
 
 +
{{Warning|The following example is dated and may no longer be accurate.}}
  
you then look for the sections that name your video card as an example mine is here:
+
As an example: For a total of 256 MB of graphics memory, the forumla is 2^28 (two to the twenty-eighth power). Approximately 64 MB could be left for graphics memory and as such the start range for the swap usage of graphics memory would be calculated with the formula 2^26.
  
<pre>
+
Using the numbers above, you can take the difference and determine a reseasonable range for usage as swap memory.
01:00.0 VGA compatible controller: ATI Technologies Inc RV350 AR [Radeon 9600] (prog-if 00 [VGA])
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leaving 2^24 (32M) for the normal function (less will work fine)
ubsystem: PC Partner Limited Unknown device 0830
+
  
ntrol: I/O+ Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR+ FastB2B-
+
==Setup==
tatus: Cap+ 66MHz+ UDF- FastB2B+ ParErr- DEVSEL=medium >TAbort- <TAbort- <MAbort- >SERR- <PERR-
+
Load the modules:
ency: 64 (2000ns min), Cache Line Size: 32 byteserrupt: pin A routed to IRQ 11
+
{{hc|# /etc/rc.conf|<nowiki>
egion 0: Memory at e0000000 (32-bit, prefetchable) [size=256M]
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MODULES=(otherModulesYouNeed '''slram mtdblock''')</nowiki>}}
egion 1: I/O ports at c800 [size=256]
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egion 2: Memory at ff8f0000 (32-bit, non-prefetchable) [size=64K]
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ion ROM at ff8c0000 [disabled] [size=128K]
+
  
ies: <access denied>
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{{hc|# /etc/rc.local|
 +
mkswap /dev/mtdblock0 && swapon /dev/mtdblock0 -p 10 #higher priority}}
  
01:00.1 Display controller: ATI Technologies Inc RV350 AR [Radeon 9600] (Secondary)
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Add the following.
ubsystem: PC Partner Limited Unknown device 0831
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{{hc|# /etc/modprobe.d/modprobe.conf|<nowiki>
 +
options slram map=VRAM,0xStartRange,+0xUsedAmount</nowiki>}}
  
ntrol: I/O+ Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR- FastB2B-
+
===Xorg driver config===
tatus: Cap+ 66MHz+ UDF- FastB2B+ ParErr- DEVSEL=medium >TAbort- <TAbort- <MAbort- >SERR- <PERR-
+
To keep X stable, your video driver needs to be told to use less than the detected videoram.
ency: 64 (2000ns min), Cache Line Size: 32 bytes
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egion 0: Memory at d0000000 (32-bit, prefetchable) [size=256M]
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egion 1: Memory at ff8e0000 (32-bit, non-prefetchable) [size=64K]
+
ies: <access denied>
+
</pre>
+
  
So what's important is the Region 0 (it seems possible to use the addresses of either the primary or secondary)
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{{hc|# /etc/X11/xorg.conf|
 +
Section "Device"
 +
    Driver "radeon" # or whichever other driver you use
 +
    VideoRam 32768
 +
#other stuff
 +
EndSection}}
 +
The above example specifies that you use 32 MB of graphics memory.
  
The video card needs some ram to function as a video card, and this space you leave at the start of the address range. Choose how much space you can spare; maybe it is 16MiB which is 0x01000000. or maybe some more.
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{{Note|Some drivers might take the number for videoram as being in MiB. See relevant manpages.}}
  
Your start of the range is then the sum of that offset and the initial address range: I would have added 0x01000000 to 0xe00000000 to get the start
+
==Troubleshooting==
 +
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>
+
{{bc|swapon -s}}
# for using vram as swap
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modprobe slram map=VRAM,0xSTART RANGE HERE,0xEND
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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
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</pre>
+
  
==External Links==
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==See also==
[http://www.linux-mtd.infradead.org MTD website]
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* [http://www.gentoo-wiki.info/TIP_Use_memory_on_video_card_as_swap Archived Gentoo Wiki articles. Note the warnings.]
[http://gentoo-wiki.com/TIP_Use_memory_on_video_card_as_swap Gentoo Wiki]
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* [http://www.linux-mtd.infradead.org MTD website]
 +
* [http://en.gentoo-wiki.com/wiki/Using_Graphics_Card_Memory_as_Swap Gentoo Wiki]{{Dead link|2013|08|17}}

Revision as of 17:36, 26 March 2014

Tango-view-fullscreen.pngThis article or section needs expansion.Tango-view-fullscreen.png

Reason: This article may need to be expanded or revised for contemporary hardware. (Discuss in Talk:Swap on video ram#)

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

Reason: Graphics hardware referenced is quite old at this point. rconf is referenced instead of systemd. This article primarily references a now archived article from Gentoo's wiki. (Discuss in Talk:Swap on video ram#)

Related articles

A short article on utilizing video memory for system swap.

Warning: This will not work with binary drivers.
Warning: Unless your graphics driver can be made to use less ram than is detected, Xorg may crash when you try to use the same section of RAM to store textures as swap. Using a video driver that allows you to override videoram should increase stability.

Potential benefits

A graphics card with GDDR SDRAM or DDR SDRAM may be used as swap by using the MTD subsystem of the kernel. Systems with dedicated graphics memory of 256 MB or greater which also have limited amounts of system memory (DDR SDRAM) may benefit the most from this type of setup.

Warning: The accelerated graphics bus (AGP) is a legacy bus and has a limited amount of bus bandwidth. This may limit reads to approximately 8 MB per second.

Kernel requirements

MTD is in the mainline kernel since version 2.6.23.

Pre-setup

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.

To find the available memory ranges run the following command and look for the VGA compatible controller section (see the example below).

$ lspci -vvv
01:00.0 VGA compatible controller: NVIDIA Corporation GK104 [GeForce GTX 670] (rev a1) (prog-if 00 [VGA controller])
	Subsystem: ASUSTeK Computer Inc. Device 8405
	Control: I/O+ Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR- FastB2B- DisINTx-
	Status: Cap+ 66MHz- UDF- FastB2B- ParErr- DEVSEL=fast >TAbort- <TAbort- <MAbort- >SERR- <PERR- INTx-
	Latency: 0
	Interrupt: pin A routed to IRQ 57
	Region 0: Memory at f5000000 (32-bit, non-prefetchable) [size=16M]
	Region 1: Memory at e8000000 (64-bit, prefetchable) [size=128M]
	Region 3: Memory at f0000000 (64-bit, prefetchable) [size=32M]
	Region 5: I/O ports at e000 [size=128]
	[virtual] Expansion ROM at f6000000 [disabled] [size=512K]
	Capabilities: <access denied>
	Kernel driver in use: nvidia
	Kernel modules: nouveau, nvidia
Note: Systems with multiple GPUs will likely have multiple entries here.

Of most potential benefit is a region that is prefectable, 64-bit, and the largest in size.

Note: The graphics card used above has 2 GB of GDDR5 SDRAM, though as indicated above the full amount is not exposed or listed by the command provided above.

A video card needs some of its memory to function, as such some calculations are needed. The offsets are easy to calculate as powers of 2. The card should use the beginning of the address range as a framebuffer for textures and such. However, if limited or as indicated in the beginning of this article, if two programs try to write to the same sectors, stability issues are likely to occur.

Warning: The following example is dated and may no longer be accurate.

As an example: For a total of 256 MB of graphics memory, the forumla is 2^28 (two to the twenty-eighth power). Approximately 64 MB could be left for graphics memory and as such the start range for the swap usage of graphics memory would be calculated with the formula 2^26.

Using the numbers above, you can take the difference and determine a reseasonable range for usage as swap memory. leaving 2^24 (32M) for the normal function (less will work fine)

Setup

Load the modules:

# /etc/rc.conf
 MODULES=(otherModulesYouNeed '''slram mtdblock''')
# /etc/rc.local
 mkswap /dev/mtdblock0 && swapon /dev/mtdblock0 -p 10 #higher priority

Add the following.

# /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.

# /etc/X11/xorg.conf
Section "Device"
    Driver "radeon" # or whichever other driver you use
    VideoRam 32768
	#other stuff
EndSection

The above example specifies that you use 32 MB of graphics memory.

Note: Some drivers might take the number for videoram as being in MiB. See relevant manpages.

Troubleshooting

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

See also