Thread: Using Micro SD Card as Virtual Ram on Nokia N900?
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Alex Atkin UK is offline Alex Atkin UK
2010-03-22 , 06:19
Posts: 716 | Thanked: 303 times | Joined on Sep 2009 @ Sheffield, UK
#16
Originally Posted by nightfire View Post
If anyone is curious, I submit that moving your swap to your microsdhc card dramatically increases performance. It offloads swap I/O from the internal MMC, which frees it up for concurrent access (ie. program/library loading).

I created a 512mb slice on my microsd card, and modified the boot scripts to use it instead (excluding the 768mb mmc swap area completely) and the device is significantly more responsive when you have more than a few processes running.

This should be an option out-of-the-box (assuming the user is fairly warned about being unable to eject the microsdhc card while running).

Also note that you need a separate partition; a swap file seems to lock /sbin/swapon (bug?), and in any case you'd lose the ability to mount the vfat partition via USB (filesystem in use).
Except, the most common programs/libraries are stored on the root partition, which is its own dedicated much faster flash memory built-in to the CPU package.

Only optified programs are stored on the eMMC, the same flash chip used for swap. So it should only make a difference in certain very specific circumstances. There is also a question of how the bus works in the N900, for all we know the microSD and eMMC have to contend for the same bandwidth.

Obviously that does not explain your positive results of moving the swap to microSD though. I usually find the N900 far more responsive after a reboot anyway, so are you sure you are not mistaking fresh boot speediness for swap speed improvement?

If it does help though, why not keep both swap partitions? Surely it being able to stripe between two separate devices should be even faster still?
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Last edited by Alex Atkin UK; 2010-03-22 at 06:23.
 

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