Difference between revisions of "Swap on video ram"

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(update for inclusion of MTD to kernel26)
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{{out of date}}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}}
+
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.
+
  
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===
Get a kernel version >= 2.6.23.1-6
+
MTD is now included in the kernel as of 2.6.23.1-6.
 +
 
 
===Post-Kernel Stuff===
 
===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.
 
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  
 
check the ranges with  
<pre>lspci -vvv</pre>
+
lspci -vvv
  
you then look for the sections that name your video card as an example mine is here:
+
Then you look for the sections that name your video card as an example mine is here:
  
 
<pre>
 
<pre>
01:00.0 VGA compatible controller: ATI Technologies Inc RV350 AR [Radeon 9600] (prog-if 00 [VGA])
+
01:00.0 VGA compatible controller: ATI Technologies Inc RV350 AR [Radeon 9600] (prog-if 00 [VGA controller])
ubsystem: 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- 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>
  
ntrol: I/O+ Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR+ FastB2B-
+
01:00.1 Display controller: ATI Technologies Inc RV350 AR [Radeon 9600] (Secondary)
tatus: Cap+ 66MHz+ UDF- FastB2B+ ParErr- DEVSEL=medium >TAbort- <TAbort- <MAbort- >SERR- <PERR-
+
Subsystem: PC Partner Limited Unknown device 0831
ency: 64 (2000ns min), Cache Line Size: 32 byteserrupt: pin A routed to IRQ 11
+
Control: I/O+ Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR- FastB2B- DisINTx-
egion 0: Memory at e0000000 (32-bit, prefetchable) [size=256M]
+
Status: Cap+ 66MHz+ UDF- FastB2B+ ParErr- DEVSEL=medium >TAbort- <TAbort- <MAbort- >SERR- <PERR- INTx-
egion 1: I/O ports at c800 [size=256]
+
Latency: 64 (2000ns min), Cache Line Size: 32 bytes
egion 2: Memory at ff8f0000 (32-bit, non-prefetchable) [size=64K]
+
Region 0: Memory at d0000000 (32-bit, prefetchable) [size=256M]
ion ROM at ff8c0000 [disabled] [size=128K]
+
Region 1: Memory at ff8e0000 (32-bit, non-prefetchable) [size=64K]
 +
Capabilities: <access denied>
 +
</pre>
  
ies: <access denied>
+
What's important is Region 0, (the biggest one)
  
01:00.1 Display controller: ATI Technologies Inc RV350 AR [Radeon 9600] (Secondary)
+
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).
ubsystem: PC Partner Limited Unknown device 0831
+
  
ntrol: I/O+ Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR- FastB2B-
+
Example: total 2^28 bytes (256M) videoram, leaving 2^24 (32M) for the normal function (less will work fine)
tatus: Cap+ 66MHz+ UDF- FastB2B+ ParErr- DEVSEL=medium >TAbort- <TAbort- <MAbort- >SERR- <PERR-
+
The start range, is 2^24 bytes more than the start of the pci address range shown by lspci -vvv.
ency: 64 (2000ns min), Cache Line Size: 32 bytes
+
egion 0: Memory at d0000000 (32-bit, prefetchable) [size=256M]
+
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)
+
The end is your total minus the amount you left for the card.
  
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.
+
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.
  
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
+
==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>
 
<pre>
# for using vram as swap
+
swapon -s
modprobe slram map=VRAM,0xSTART RANGE HERE,0xEND
+
modprobe mtdchar #probably unnecessary
+
modprobe mtdblock
+
mkswap /dev/mtdblock0
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swapon /dev/mtdblock0 -p 10 #higher priority gets used before disk
+
 
</pre>
 
</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]
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*[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