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tirsales · 11-09-2007, 08:22 AM

Hi there,

as a warning note in advance: Currently I don't own an iLiad, nor do I have access to one ATM. Thus this is a purely theoretical approach and I don't have the means needed to implement this myself (okay, I could implement this, but I couldn't test it).

My questions:

1. I have read multiple times, that enabling swap would be a nice thing. Though I know why swap sometimes is a nice thing on a normal system, I don't see the main advantage for the iLiad: CF is relatively slow, thus I can't see a big improvement through this (okay, perhaps when running multiple applications).
Same applies to SD. I don't know if the DOC is faster, problems see at the bottom, alternative 1.

With a (not too-low quality) modern CF/SD card the number of read/write cycles shouldn't be too much of a problem (a number of embedded device manufacturers actually deliever devices using CF, allowing for swap and giving a 3-year-warranty). This specifically excludes any "standard CF"-cards (like SanDisk Standard vs SanDisk Extreme, Ultra, etc) as they typically allow for only a limited number of write cycles. And even if killed after a year, cards are cheap.

2. What is the big problem?
AFAIK one can install a new kernel to the iLiad via the CF-Bootloader. Correct?
The swap-utilities themselves should be available for XScale-cpus and an ARM-architecture already. Granted, I haven't had a bigger look into this, but I know for sure that the ARM-port of debian allows for swap ...

Thus one should be (easily) able to port a swap-enabled kernel & -utility to the iLiad. For enabling swap:
Write a short shellscript that tests for a CF-card and wether partition 2 on this card (yes, CF can be partitioned) and, if present and a swap-partition, enables swapping to that partition.
Write a second shellscript that disables swapping (in case you want to extract the card).
It wouldn't even be needed to put the swap-modules into initrd, loading them sometime (when needed) is sufficient. It wouldn't even need to be a startscript but could be run when needed (thus reducing the power drain when swap is not needed).

Big drawback: Power drain. CF sucks power, swapping would be (in the worst case) a continuous writing/reading to that card and thus would kill your battery time for good.

Alternative 1: Repartition the iLiad-intern flash device, enabling an intern swap.
I wouldn't recommand this though:
CF/SD Cards are cheap, thus it is not a big problem if they scrumble after 1-3 years. ATM I don't know which DOC is used, thus I cannot say the number of write-cycles it supports (and I am too lazy to search). But ntl: Killing your DOC-chip (thus needing a new iLiad) is far more expensive than killing your CF/SD card (thus needing a new card). Not worth the (possible) gain IMO.

Alternative 2: Use a SD-card instead of CF (if they use less power). I don't even know wether SD-cards can be partitioned, but it should be possible to either use the complete card or use a swap-file.

Alternative 3: Use a swap-file on the DOC. Problems: see alternative1. Advantage: no need to repartition the DOC.

This thread is to be ignored or regarded at your own judgement

regards

Tirsales

11-09-2007, 08:22 AM	#1
tirsales MIA ... but returning som Posts: 1,600 Karma: 511342 Join Date: Nov 2007 Location: Germany Device: PRS-505 and Really not owning a PRS-700	SWAP on iLiad Hi there, as a warning note in advance: Currently I don't own an iLiad, nor do I have access to one ATM. Thus this is a purely theoretical approach and I don't have the means needed to implement this myself (okay, I could implement this, but I couldn't test it). My questions: 1. I have read multiple times, that enabling swap would be a nice thing. Though I know why swap sometimes is a nice thing on a normal system, I don't see the main advantage for the iLiad: CF is relatively slow, thus I can't see a big improvement through this (okay, perhaps when running multiple applications). Same applies to SD. I don't know if the DOC is faster, problems see at the bottom, alternative 1. With a (not too-low quality) modern CF/SD card the number of read/write cycles shouldn't be too much of a problem (a number of embedded device manufacturers actually deliever devices using CF, allowing for swap and giving a 3-year-warranty). This specifically excludes any "standard CF"-cards (like SanDisk Standard vs SanDisk Extreme, Ultra, etc) as they typically allow for only a limited number of write cycles. And even if killed after a year, cards are cheap. 2. What is the big problem? AFAIK one can install a new kernel to the iLiad via the CF-Bootloader. Correct? The swap-utilities themselves should be available for XScale-cpus and an ARM-architecture already. Granted, I haven't had a bigger look into this, but I know for sure that the ARM-port of debian allows for swap ... Thus one should be (easily) able to port a swap-enabled kernel & -utility to the iLiad. For enabling swap: Write a short shellscript that tests for a CF-card and wether partition 2 on this card (yes, CF can be partitioned) and, if present and a swap-partition, enables swapping to that partition. Write a second shellscript that disables swapping (in case you want to extract the card). It wouldn't even be needed to put the swap-modules into initrd, loading them sometime (when needed) is sufficient. It wouldn't even need to be a startscript but could be run when needed (thus reducing the power drain when swap is not needed). Big drawback: Power drain. CF sucks power, swapping would be (in the worst case) a continuous writing/reading to that card and thus would kill your battery time for good. Alternative 1: Repartition the iLiad-intern flash device, enabling an intern swap. I wouldn't recommand this though: CF/SD Cards are cheap, thus it is not a big problem if they scrumble after 1-3 years. ATM I don't know which DOC is used, thus I cannot say the number of write-cycles it supports (and I am too lazy to search). But ntl: Killing your DOC-chip (thus needing a new iLiad) is far more expensive than killing your CF/SD card (thus needing a new card). Not worth the (possible) gain IMO. Alternative 2: Use a SD-card instead of CF (if they use less power). I don't even know wether SD-cards can be partitioned, but it should be possible to either use the complete card or use a swap-file. Alternative 3: Use a swap-file on the DOC. Problems: see alternative1. Advantage: no need to repartition the DOC. This thread is to be ignored or regarded at your own judgement regards Tirsales Last edited by tirsales; 11-09-2007 at 11:21 AM.