Difference between revisions of "Swap on video ram"

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(describe how to limit VideoRam taken by X)
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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{{Out of date|Graphics hardware referenced is quite old at this point.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.}}
Warning: the stuff in here is not tested that much, and it is possible that you may have a conflict and your xserver will crash.
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{{Article summary start}}
To be absolutely sure of stability, use an xorg driver that allows you to override videoram. At least the vga and radeon (xf86-video-ati) listen to an overide.
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{{Article summary text|A short article on utilizing video memory for system swap.}}
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{{Article summary heading|Related}}
 +
{{Article summary wiki|Maximizing Performance}}
 +
{{Article summary end}}
 +
{{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.}}
  
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. MTD is now included in kernel26.
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==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.
  
==How To==
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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 Stuff===
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Get a kernel version >= 2.6.23.1-6
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==Kernel requirements==
===Post-Kernel Stuff===
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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>
+
  
Then you look for the sections that name your video card as an example mine is here:
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{{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>}}
  
<pre>
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{{Note|Systems with multiple GPUs will likely have multiple entries here.}}
01:00.0 VGA compatible controller: ATI Technologies Inc RV350 AR [Radeon 9600] (prog-if 00 [VGA])
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ubsystem: PC Partner Limited Unknown device 0830
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ntrol: I/O+ Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR+ FastB2B-
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Of most potential benefit is a region that is prefectable, 64-bit, and the largest in size.
tatus: Cap+ 66MHz+ UDF- FastB2B+ ParErr- DEVSEL=medium >TAbort- <TAbort- <MAbort- >SERR- <PERR-
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{{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.}}
ency: 64 (2000ns min), Cache Line Size: 32 byteserrupt: pin A routed to IRQ 11
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egion 0: Memory at e0000000 (32-bit, prefetchable) [size=256M]
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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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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.
  
01:00.1 Display controller: ATI Technologies Inc RV350 AR [Radeon 9600] (Secondary)
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{{Warning|The following example is dated and may no longer be accurate.}}
ubsystem: PC Partner Limited Unknown device 0831
+
  
ntrol: I/O+ Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR- FastB2B-
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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.
tatus: Cap+ 66MHz+ UDF- FastB2B+ ParErr- DEVSEL=medium >TAbort- <TAbort- <MAbort- >SERR- <PERR-
+
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]
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ies: <access denied>
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</pre>
+
  
What's important is Region 0, (the biggest one)  
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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)
  
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 uses the begining of the address range as framebuffer, textures etc. when it is limited (pretty sure about this, but maybe your driver could be different).
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==Setup==
 +
Load the modules:
 +
{{hc|# /etc/rc.conf|<nowiki>
 +
MODULES=(otherModulesYouNeed '''slram mtdblock''')</nowiki>}}
  
Example: total 2^28 bytes (256M) videoram, leaving 2^24 (32M) for the normal function (less will work fine)
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{{hc|# /etc/rc.local|
The start range, is 2^24 bytes more than the start of the pci address range shown by lspci -vvv.
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mkswap /dev/mtdblock0 && swapon /dev/mtdblock0 -p 10 #higher priority}}
  
The end is your total minus the amount you left for the card.  
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Add the following.
 +
{{hc|# /etc/modprobe.d/modprobe.conf|<nowiki>
 +
options slram map=VRAM,0xStartRange,+0xUsedAmount</nowiki>}}
  
<pre>
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===Xorg driver config===
# for using vram as swap
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To keep X stable, your video driver needs to be told to use less than the detected videoram.
modprobe mtdblock slram map=VRAM,0xSTART RANGE,+0xWHAT IS USED
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mkswap /dev/mtdblock0
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swapon /dev/mtdblock0 -p 10 #higher priority to be swapped to before disk
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</pre>
+
  
=Xorg Driver Config=
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{{hc|# /etc/X11/xorg.conf|
To keep X stable, you have to tell your video driver to take a small part of the videoram. In the Device section of your /etc/X11/xorg.conf the declaration
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<pre>
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Section "Device"
 
Section "Device"
     Driver "radeon"
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     Driver "radeon" # or whichever other driver you use
 
     VideoRam 32768
 
     VideoRam 32768
EndSection
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#other stuff
</pre>
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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.
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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
 +
 
 +
{{bc|swapon -s}}
  
==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]{{linkrot|2013|08|17}}

Revision as of 04:30, 18 August 2013

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#)
Template:Article summary start

Template:Article summary text Template:Article summary heading Template:Article summary wiki Template:Article summary end

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