MobileRead Forums - View Single Post - Using swap on a PW-3

knc1 · 02-15-2016, 12:08 PM

On a PW-3 (G090 G1 - fw-5.6.1.1), 512Mbyte Ram, 4Gbyte eMMC ::

Using the system feature that /var/local is always mounted; either in 'main' or 'diags'.

Setup to use 1/4 of /var/local for a system swap file.

Over ssh (or telnet or serial port or from kTerm) -

Code:

[root@kindle root]# cd /var/local

[root@kindle local]# df .
Filesystem           1K-blocks      Used Available Use% Mounted on
/dev/mmcblk0p3           63461     16692     43493  28% /var/local

Note that the PW-3 has a /var/local partition twice the size of what it was on the KT.
The Busybox/Ash command line can do simple math, find number of erase blocks:

Code:

[root@kindle local]# echo $((1024*1024*16/4096))
4096

Linux swap files **must** be initialized to zeros (no sparse files allowed):

Code:

[root@kindle local]# dd if=/dev/zero of=swap bs=4096 count=4096
4096+0 records in
4096+0 records out
16777216 bytes (16.0MB) copied, 0.627486 seconds, 25.5MB/s

Interesting, the 'bulk write' on the PW-3 eMMC is 1/2 the rate as on the KT eMMC. ( ? )
The swap file requires a special format:

Code:

[root@kindle local]# mkswap ./swap
Setting up swapspace version 1, size = 16773 kB
no label, UUID=abd86682-51a1-42f6-aede-228fea736287

The above completes the (one-time) setup of a PW-3 swapfile.
Its use by the system is controlled by the swapon and swapoff commands.

Code:

[root@kindle local]# swapon ./swap
[root@kindle local]# free
             total       used       free     shared    buffers     cached
Mem:        515344     503292      12052          0     291540      54556
-/+ buffers/cache:     157196     358148
Swap:        16016          0      16016

Now open Kindle Paperwhite User's Guide

Code:

[root@kindle local]# free
             total       used       free     shared    buffers     cached
Mem:        515344     500168      15176          0     275520      60604
-/+ buffers/cache:     164044     351300
Swap:        16016       2412      13604

Browse the user's guide.
Then close Kindle Paperwhite User's Guide

Code:

[root@kindle local]# swapon -s
Filename                                Type            Size    Used    Priority
/var/local/swap                         file            16016   1556    -1

[root@kindle local]# df .
Filesystem           1K-blocks      Used Available Use% Mounted on
/dev/mmcblk0p3           63461     33148     27037  55% /var/local

For users with a lot of books, perhaps using only 8Mbyte (half the above size) for the swap file would be a better choice.
Even using only 2Mbyte of file space for the swap file reduces the kernel's page management workload.

To the end-user, the appearent change is a more responsive Kindle.

Since the above steps do not make an addition to /etc/fstab, the use of the swap file will 'go away' with the next re-boot.

That is: the 'swapon /var/local/swap' command needs to re-issued after each reboot (the normal system shutdown will take care of the 'swapoff' process).

When (IF) I get the spare time, I'll create a KUAL extension button (set) to let the non-technical user deal with all of the above.

Note 1:
If your 'main' system chokes by running out of space on /var/local -
just re-boot into 'diags' and remove the /var/local/swap file.
An easy way to do that, is to have RP (Rescue Pack) installed.
The RP re-enables the recognition of the flag file: ENABLE_DIAGS, previously last seen on the KT.

Note 2:
Other directions you find may say to put the swap file in user storage.
Not a good idea, because the Kernel can't access user storage when it is exported as mass storage over USB.
And the Kernel really, really does not like to have the backing store of its swap file suddenly disappear.

02-15-2016, 12:08 PM	#1
knc1 Going Viral Posts: 17,212 Karma: 18210809 Join Date: Feb 2012 Location: Central Texas Device: No K1, PW2, KV, KOA	Using swap on a PW-3 On a PW-3 (G090 G1 - fw-5.6.1.1), 512Mbyte Ram, 4Gbyte eMMC :: Using the system feature that /var/local is always mounted; either in 'main' or 'diags'. Setup to use 1/4 of /var/local for a system swap file. Over ssh (or telnet or serial port or from kTerm) - Code: [root@kindle root]# cd /var/local [root@kindle local]# df . Filesystem 1K-blocks Used Available Use% Mounted on /dev/mmcblk0p3 63461 16692 43493 28% /var/local Note that the PW-3 has a /var/local partition twice the size of what it was on the KT. The Busybox/Ash command line can do simple math, find number of erase blocks: Code: [root@kindle local]# echo $((1024102416/4096)) 4096 Linux swap files must be initialized to zeros (no sparse files allowed): Code: [root@kindle local]# dd if=/dev/zero of=swap bs=4096 count=4096 4096+0 records in 4096+0 records out 16777216 bytes (16.0MB) copied, 0.627486 seconds, 25.5MB/s Interesting, the 'bulk write' on the PW-3 eMMC is 1/2 the rate as on the KT eMMC. ( ? ) The swap file requires a special format: Code: [root@kindle local]# mkswap ./swap Setting up swapspace version 1, size = 16773 kB no label, UUID=abd86682-51a1-42f6-aede-228fea736287 The above completes the (one-time) setup of a PW-3 swapfile. Its use by the system is controlled by the swapon and swapoff commands. Code: [root@kindle local]# swapon ./swap [root@kindle local]# free total used free shared buffers cached Mem: 515344 503292 12052 0 291540 54556 -/+ buffers/cache: 157196 358148 Swap: 16016 0 16016 Now open Kindle Paperwhite User's Guide Code: [root@kindle local]# free total used free shared buffers cached Mem: 515344 500168 15176 0 275520 60604 -/+ buffers/cache: 164044 351300 Swap: 16016 2412 13604 Browse the user's guide. Then close Kindle Paperwhite User's Guide Code: [root@kindle local]# swapon -s Filename Type Size Used Priority /var/local/swap file 16016 1556 -1 [root@kindle local]# df . Filesystem 1K-blocks Used Available Use% Mounted on /dev/mmcblk0p3 63461 33148 27037 55% /var/local For users with a lot of books, perhaps using only 8Mbyte (half the above size) for the swap file would be a better choice. Even using only 2Mbyte of file space for the swap file reduces the kernel's page management workload. To the end-user, the appearent change is a more responsive Kindle. Since the above steps do not make an addition to /etc/fstab, the use of the swap file will 'go away' with the next re-boot. That is: the 'swapon /var/local/swap' command needs to re-issued after each reboot (the normal system shutdown will take care of the 'swapoff' process). When (IF) I get the spare time, I'll create a KUAL extension button (set) to let the non-technical user deal with all of the above. Note 1: If your 'main' system chokes by running out of space on /var/local - just re-boot into 'diags' and remove the /var/local/swap file. An easy way to do that, is to have RP (Rescue Pack) installed. The RP re-enables the recognition of the flag file: ENABLE_DIAGS, previously last seen on the KT. Note 2: Other directions you find may say to put the swap file in user storage. Not a good idea, because the Kernel can't access user storage when it is exported as mass storage over USB. And the Kernel really, really does not like to have the backing store of its swap file suddenly disappear.