JayotisDiggory
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| The reason for this swap setup is to eliminate using a slow, mechanical, Hard Drive(HD) as a swap device. The HD is a bottleneck due to a physical arm that needs to move to each bit of data before it can be sent to RAM. With USB flash memory devices, memory is accessed in RAM fashion and no movement(aside from electrons) is required; this also means that __fragmentation of the page file does not effect data access times__. Data read speeds on these devices are far faster then that of a conventional HD. When a page is requested to be placed into physical memory, it happens almost instantly. Since the write operations are slower then read, multiple devices are used to multi-task the process on a hardware level. | The reason for this swap setup is to eliminate using a slow, mechanical, Hard Drive(HD) as a swap device. The HD is a bottleneck due to a physical arm that needs to move to each bit of data before it can be sent to RAM. With USB flash memory devices, memory is accessed in RAM fashion and no movement(aside from electrons) is required; this also means that __fragmentation of the page file does not effect data access times__. When a page is requested to be placed into physical memory, it happens almost instantly. Since the write operations are slower then read, multiple devices are used to multi-task the process on a hardware level. |
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| ''only 4 USB2.0 ports & 4 identical make/model USB2.0 storage devices are needed'' | ''Only 4 USB2.0 ports & 4 identical make/model USB2.0 Flash memory storage devices 256MB or more are needed. You can get away with a 4 port hub although I've never tried. Also, the use of more devices may improve performance even further...'' |
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| 1. Partition and format the 4 USB2.0 storage devices as linux swap.[[BR]] | 1. Partition and format the 4 storage devices as linux swap.[[BR]] |
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| 7. Edit '''''/etc/init.d/bootmisc.sh''''' and look for {{{ # Remove bootclean's flag files. # Don't run bootclean again after this! rm -f /tmp/.clean}}} [[BR]] add these lines below it {{{ echo 1024 > /sys/block/sda/device/max_sectors echo 1024 > /sys/block/sdb/device/max_sectors echo 1024 > /sys/block/sdc/device/max_sectors echo 1024 > /sys/block/sdd/device/max_sectors swapon -a}}} Note1: This is my device layout, your device names(sd*) maybe different. A hub ''may'' also need its max_sector changed. Note2: I am not sure if bootmisc.sh is best place for these commands, it seems max_sectors gets overwritten anywhere before this script. If you know of a better way(not udev rule) then please let me know. |
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| 8. Check to see if your swap devices are activated with `swapon -s` ; if yes then your done... if no then please read the known bugs. | 8. Check to see if your swap devices are activated with `swapon -s` ; if yes then your done... if no then please contact me. |
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| === Known bugs === On restart Ubuntu did not turn on the new swap devices for me, if this happen to you as well you can turn them on manually with `swapon -a` or place the command inside a startup script which runs before the desktop is loaded. I inserted a syslink '''''S04swapsys''''' into '''''rc5.d''''' pointing to a script called '''''swapsys''''' located at '''''/etc/init.d''''' which looked like this {{{#! /bin/sh # PATH=/bin:/usr/bin:/sbin:/usr/sbin swapon -a exit 0}}} |
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'''Warning'''[[BR]] I have noticed that my fans (GPU, CPU or both) rev up to a pitch I've never heard before. While my system has hardware fail-safes built into them, I don't want to find them and only run all programs for a couple of minutes. [[BR]] |
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| `man swapon(2)` priority option | `man swapon(2)` -p priority |
ContentsBRTableOfContents |
Introduction
I am very interested in the paging functions of the kernel. This is due to several blown hard drives which I believe where thrashed to death by page swapping and system file reads... (i.e. swap partition and root/data on same device.) So I decided to replace the typical swap set up with one that didn't rely on a mechanical device which is prone to failure. In doing so I have increased the performance of my system by 50% overall, and an astounding 200% in some cases of heavy paging activity.
How to Manage Swap Space
The reason for this swap setup is to eliminate using a slow, mechanical, Hard Drive(HD) as a swap device. The HD is a bottleneck due to a physical arm that needs to move to each bit of data before it can be sent to RAM. With USB flash memory devices, memory is accessed in RAM fashion and no movement(aside from electrons) is required; this also means that fragmentation of the page file does not effect data access times. When a page is requested to be placed into physical memory, it happens almost instantly. Since the write operations are slower then read, multiple devices are used to multi-task the process on a hardware level.
Setup procedure
Only 4 USB2.0 ports & 4 identical make/model USB2.0 Flash memory storage devices 256MB or more are needed. You can get away with a 4 port hub although I've never tried. Also, the use of more devices may improve performance even further...
1. Partition and format the 4 storage devices as linux swap.BR 2. Reboot.BR 3. Open gparted, check the devices are present, in proper format and their names.BR 4. Edit /etc/fstab and add the following lines
{{{/dev/sda1 none swap sw,pri=10 0 0 /dev/sdb1 none swap sw,pri=10 0 0 /dev/sdc1 none swap sw,pri=10 0 0 /dev/sdd1 none swap sw,pri=10 0 0}}}
- Note: the device names should match what is shown by gparted.
5. You should also see the original swap partition with a pri= value, change that too pri=0 if it is not already. You want to have a Hard Disk swap partition as a fall back measure. {{{#example /dev/hdc2 none swap sw,pri=0 0 0 }}}
6. Save fstab.BR 7. Edit /etc/init.d/bootmisc.sh and look for {{{ # Remove bootclean's flag files.
- # Don't run bootclean again after this!
rm -f /tmp/.clean}}} BR
add these lines below it {{{ echo 1024 > /sys/block/sda/device/max_sectors
echo 1024 > /sys/block/sdb/device/max_sectors echo 1024 > /sys/block/sdc/device/max_sectors echo 1024 > /sys/block/sdd/device/max_sectors swapon -a}}}
Note1: This is my device layout, your device names(sd*) maybe different. A hub may also need its max_sector changed. Note2: I am not sure if bootmisc.sh is best place for these commands, it seems max_sectors gets overwritten anywhere before this script. If you know of a better way(not udev rule) then please let me know.
7. Restart machine. BR 8. Check to see if your swap devices are activated with swapon -s ; if yes then your done... if no then please contact me.
Testing
WarningBR I have noticed that my fans (GPU, CPU or both) rev up to a pitch I've never heard before. While my system has hardware fail-safes built into them, I don't want to find them and only run all programs for a couple of minutes. BR
I have been testing this setup with excellent results using the following software:
-Wine-> World of Warcraft(windowed mode)
-Firefox->flash & graphic pages
-Azureus-> large file download.
-Mplayer-> playing movie
-xmms->music stream
These are all running at the same time and I am focus switching back and forth with no problems, very fast results.
WoW running by itself is where I get the 200% value. It is based on how long it takes to reload large areas and how long it takes move when entering populated cities and areas. The game runs smoother, faster and is more stable then running it on the OS it was designed for.
Also see
man swapon(2) -p priority
JayotisDiggory (last edited 2008-08-06 17:00:40 by localhost)