Database Develop

Question about swap and swapper 2 (recreate/reformat swap)

Hi!
I have a question about swap and swapper 2. Under advanced tab in swapper 2 there are two options: "recreate swap file" and "reformat swap". Is there any benefit in keeping these two options on? Don't they make enabling swap take longer and additionally decrease SD card life (since the file is constantly being removed and recreated)?
Sorry if it's already been mentioned somewhere but I couldn't find a satisfying answer. I only found some posts telling to tick these two options but without telling why they should be ticked.

Well? Does anyone know the answer?

For the sd life, You just answered your very own question
and for the "recreate swap file" and "reformat swap" options, it brings no differences at all. Because when the phone reboot, it contain previous swap memory intact, but when you open an application (use the swap) it will automatically cleared with an unnoticable delay. While the option "recreate swap file" and "reformat swap" will increase booting time
i used kernel embedded swap, so doesn't very sure

What about swappiness? I currently have 256mb of swap and I tried both 10 and 100 swappiness. From what I've read 100 is supposed to result in some major system performance hit but I didn't notice anything bad happening. Would setting it to 10 mean that the phone will eventually run out of RAM and force close foreground app (like it often happens without swap)?
When we consider only the foreground active app (e.g. a RAM demanding game) is it better to have 10 or 100 swappiness? Also how much swap is too much and why?

CuriousJack said:
What about swappiness? I currently have 256mb of swap and I tried both 10 and 100 swappiness. From what I've read 100 is supposed to result in some major system performance hit but I didn't notice anything bad happening. Would setting it to 10 mean that the phone will eventually run out of RAM and force close foreground app (like it often happens without swap)?
When we consider only the foreground active app (e.g. a RAM demanding game) is it better to have 10 or 100 swappiness? Also how much swap is too much and why?
Click to expand...
Click to collapse
well, swappiness value alter the system which memory to use the most,
e.g. 0 will use ram until it full then slowly fill the swap, otherwise 100 inverted result.
it is recommended to set swap between 30-90, as the ram have lesser latency and for normal usage(i can play angry grand with 49 swappiness, starting lag abit then it smoothed).
for heavy gamer, you will need set from 60 to 100 as you needed.
and for swap capacity, the more the good . if your swap are more enough, android tend to keep most of the application you used the most keep in memory so, the next time you open that app, it will be fast
and for need of swap capacity more than 256mb, you'll need use partition wizard to make it

[Q] Now, what is it with the free ram?

So here I am running Infinitum (AOKP) v2.1 with Devil2 0.72, 402 MB edition.
So this is the amount of free ram I have:
~20 MB. *click*
NO WAIT! its 150 MB! *click*
errr... no... its still just ~20 MB *click*
So why would android tell me I got 150 MB of free ram and 'free' command tells me something quiet different? I really don't get it, hope some1 can enlighten me :/
Thanks!

Many apps are cached/pre-buffered like in Windows, so in reality RAM is used more. This 150MB physically is not free, but it's available for apps that needs RAM - memory from this 150MB will be 'cleared' instantly.

So I am not running critically low on memory?
But I guess more ram would anyway benefit the overall performance since android could cache/pre-buffer even more, right?

You can check Memory usage with the SystemPanel app: it will list all active applications / system processes and services / cached applications , showes what amout of ram they're using and can kill the unnecesserary apps on the spot with it!

[Q] zRam vs Swap

which is the better option for performance (with respect to speed and multitasking)
As I understand it zRam compresses unused apps within the system RAM. So there is a CPU cost as well as reduced available RAM for other apps.
Swap files don't restrict available RAM but writing to the sdcard impacts the speed of opening apps.
Can both be used at the same time? I don't think so, but maybe I'm wrong. And perhaps using both has a negative impact on performance.
If only one is a viable option, which one should I use?

for me swap is better

[Q]most great set for SDCard

Just simply question guys,but I confuse about this
*swap enable/using swap partition
*using ext partition over moving apps2SD normally
Is this could be better than normal/standard SDCard?
I have Transcend 16GB Class 10 using fat32+ext4 (using link2sd)
But I felt not different with my VGen Class4 8GB
Please guys if you have experience about this,,tell whats wrong n what were I missed for
Thanks
Sent from my Spice Mi-410 using Tapatalk 2

Arya_3RDNumber said:
Just simply question guys,but I confuse about this
*swap enable/using swap partition
*using ext partition over moving apps2SD normally
Is this could be better than normal/standard SDCard?
I have Transcend 16GB Class 10 using fat32+ext4 (using link2sd)
But I felt not different with my VGen Class4 8GB
Please guys if you have experience about this,,tell whats wrong n what were I missed for
Thanks
Sent from my Spice Mi-410 using Tapatalk 2
Click to expand...
Click to collapse
I'll try to answer base from what I know....
"*swap enable/using swap partition"
About this, we have to know what is swap, swap type and do we need it?
swap is the another partition which will be used as an extra memory. As we know, memory is been accessed VERY OFTEN in a process, both read and write.
On linux PC commonly we use one partition on disk drive for linux swap. On windows it's using a file as a virtual memory.
Swap is needed when the application need large memory to be used for a process and the current ram is not enough. Well there are some priority list to be followed. Ok, I'll give an example if we run a big game in an android. we have ~350MB total user memory but let say we have 50MB free memory. Most of android BIG 3D games will not exceed 300MB of memory, the game designer will look to target phone which will run it, and they presume all user don't have swap memory. But let say the app will need about 300MB of memory to run.
1. If we have 50 MB swap partition in sdcard
Android will never deplete the real ram, so let say it will keep 10MB of free ram, it will be use for the android system rom to keep running. In this situation the app will take 40MB of free ram, 50MB of swap... and what about another 210MB? Android will take it from the real ram by kill another apps (based on priority of low memory killer setting) to reallocate the ram. So for the game, the real ram will be taken about 250MB and 50MB from swap and free ram about 10MB. another 90MB of real ram used by the system and another hidden app like framework setting, messaging and others and for app cache. About 250MB ram used by game app is accessed very fast, but 50MB of swap if very slow because of access speed of sdcard is very much slower then ram.
When exiting from the game, some hidden apps still in memory. Android will run one or two another residen apps.
2. If we have 50 MB swap zram
Zram is swap partition in real ram, not sdcard. Any data written to the zram is compressed and decompressed on the fly. For 50MB zram, let say we can get about 80MB swap because of compression. the ratio depend on data been compressed.
Just like said in point 1, android will keep 10MB of free ram for the android system rom to keep running. The app will take 40MB of free ram, 80MB of swap. The real ram is 350MB - 50MB(zram) = 300MB, 290MB will be available for apps. The app will take 80MB from zram, and use 220MB from real ram. So 290 - 220 = 70MB of ram will used by android system and for app cache.
About speed of game between those 2 swap type, zram will be faster for sure because it use ram rather then sdcard. And one thing I feel necessary to let you know. Not as in PC which using HDD as storage which almost has unlimited write cycle. But we use SDCARD which has very limited write cycle. So consider using swap partition in your sdcard, even if it has very fast write/read speed. It will significantly affect your sdcard life.
When exited from the game, few hidden app still reside in memory. Android will run few another residen apps.
3. If we not use any swap
The game will take 300MB of ram, and let 40MB of ram used by android system. More apps have to be killed by android low memory killer system.
When exited from the game, only one or two hidden app still reside in memory. Android will run some more another residen apps.
It's your decision to use swap or not. The need is depend on your behave of use of this phone and the types of apps installed, such as more widgets, tools and some residen apps. Try every option, and you will get the result. The result could be different with another user, depend on behave and the apps installed.
*using ext partition over moving apps2SD normally
If you really have your internal storage depleted, let say you have installed hundreds of apps, then yes you will need app2SD or ext partition on sdcard.
The read and write speed of internal storage and sdcard will definitely win by internal storage (You have class 10 of sdcard? just test the write speed of internal storage).
ext partition is access directly while app2SD using 3rd app, so using ext partition should be faster then app2SD.
Just 1.5 cents....
Do you understand what I've talked about???? Well.... I don't!!!

I'm a noob and it cracks my skull. Great explanation though:good:

wow??!! great explanation agan master
well I understand very much after read 1000times
Thanks a lot gan,,I must little experiment to realize
Now I understand what is "ZRAM" (sorry I really noobie )
about all this case,,is ZIPALIGN also complicate?

Well... actually my explanation hasn't completed yet. I was mentioned about priority, I didn't explained it. It about low memory killer configuration and also the priority of using swap. You can Google that .
About zipalign, it related with apk files. It intended to make it faster to load. Apk file is a compressed file. But I don't have any further knowledge regarding this. May be someone can explain it.
Sent from my bike using Tapatalk 2

[TUTORIAL] Compcache and Swap

my 2c about compcache (now "zram") and swap
Both compcache and swap are used to improve performance AND maximum number of open apps.
1)How they work:
swap is the classic way to "increase" ram on a system.
Swap is a space on a non volatile memory (="not ram") where unused ram data are parked instead of being deleted.
Swap wears(and kills) memories it is put on. It is an heavy access file. Sdcards don't like it. They are not full-featured SSD Disks. Think of your photographs
Compcache is the new way to "increase" ram on a system,
compcache :
-reserves a part of you ram (cache),
-then it looks for unused data sitting on remaining, "real", ram,
-compresses these unused data (with a very primitive,loseless, algorithm) and
- send them to its cache OR to swapfile.
Compcache's trick works well when you have lots of higly,easily, compressable data in your ram. Text is higly compressable, an executable is less compressable.
1a)
-if, after compression , data are still "big" (compressed data > original data /2), then compcache sends compressed data to swap, not to cache.
-and when compcache is full, unused compressed data are sent to swap.
2) because of compression involved, compcache uses more cpu cycles than classic swap.
3) settings of both depends on
-hardware specs of the system.
-use of the system
4) compcache+swap is better than swap alone if your ram is filled with EASILY compressable data.
4a)Remember point 1a : compcache has a simple compression algorithm, and ALWAYS first compresses data.
AFTER COMPRESSION it decides if keeping them in cache or sending them to swap. This means that
if compcache has always to work with not compressable data, it will compress them AND send to swap. this means double work: compression AND swap access.
4b) First practical conclusion :
compcache is useful for people using LOTS of text-intensive apps (forums, webpages, docs, facebook)
compcache may be useful in apps using SIMPLE still images (some games, driving assistant)
compcache is useless in multimedia activity (watching youtube, movies, photographs, listening to mp3s, playing some other games.)
5) The swap file.
As told at the beginning, swap, both improve performance(=speed) AND number of apps simultaneously open.
Lets' take a look to the PERFORMANCE thing.
5a)On "classical" (fragmented, not-SSD hard disk) systems, a swap file is always faster than retrieving datas from original disk locations. EVEN IF the swap file is on the same disk where original datas are.
This happens mainly because :
5a1)-data in swap file are less fragmented, needing less seek time.
5a2)-swap file is usually put in the external (=fast) zone of an hard disk,
5b)On SSD systems (phones included) 5a1 and 5a2 are not true, and a swapfile is USELESS IN IMPROVING PERFORMANCE EACH TIME THAT it is keeping data which are already present on its same phisycal memory.
Examples :
5b1)opera browser executable is on phone memory; but Opera-cached-webpages have been moved on sdcard via app2sd.
In this situation a swap file on sdcard is obviously useless to improve internet browsing with Opera.
5b2) i use apps (facebook, Whatsapp) which DON'T have a good caching of their own. Swap could be useful: it could avoid re-downloading data from the internet.
Now, the INCREASE MAXIMUM NUMBER OF OPEN APPS argument.
This is always true.
So:
5c)swapfile on SSD speeds up multitasking ONLY IF you use apps that
-badly manage (or don't have) a cache of their own.
-don't like force closing
Since this seems to happen very often to android apps, a swapfile is useful.
5c1)Swapfile could speed multitasking also IF an app's well-designed-cache is on a media WAY SLOWER than swapfile (but this is not LG O2x situation: it has a class10 internal memory).
So, my 2 cents about "increasing" RAM in LG O2X is :
-leave apps on phone memory, and put swap on a class10 sdcard.
-enable compcache only if you use lots of text-rich apps.

First: I think this doesn't really fit into the development section.
Then: I can't second the post you made.
mercxda said:
Both compcache and swap are used to improve performance AND maximum number of open apps.
(...)
As told at the beginning, swap, both improve performance(=speed) AND number of apps simultaneously open.
Click to expand...
Click to collapse
zRAM does NOT improve the speed of your device. Everything that's in the reserved zram storage will get compressed and decompressed, which takes some time (and cpu).
Swap is performing even worse. Instead of the fast RAM or the semi-fast compressed zRAM usage it's swapping onto the slow SD.
Sure, you can increase the maximum number of open apps, but the price is a lower performance.
So you're probably just meaning multitasking performance.
But still I can't agree to your conclusion:
mercxda said:
So, my 2 cents about "increasing" RAM in LG O2X is :
-leave apps on phone memory, and put swap on a class10 sdcard.
-enable compcache only if you use lots of text-rich apps.
Click to expand...
Click to collapse
As I wrote above zRAM is way faster than swap. So zRAM should be the first choice if you're running into low RAM situations.
If you still need more go and enable swap as well.
Last but not least:
Why are you talking about compache all the time? It's called zram nowadays, so call it that way.

tonyp said:
First: I think this doesn't really fit into the development section.
Click to expand...
Click to collapse
First : thanks for your interest in this post . I partially agree with you: this post is on the borderline beetwen Q&A and Development, because swap is not a development matter, it's standard unix's way of working.
On the other side zram's use,way of working, and even its inclusion (or not) itself in default installs, is still under development.
https://lists.ubuntu.com/archives/ubuntu-devel-discuss/2012-December/014122.html
Sure, x86/x64 is not ARM. And CM is not ubuntu.
Then: I can't second the post you made.
zRAM does NOT improve the speed of your device. Everything that's in the reserved zram storage will get compressed and decompressed, which takes some time (and cpu).
Swap is performing even worse. Instead of the fast RAM or the semi-fast compressed zRAM usage it's swapping onto the slow SD.
Sure, you can increase the maximum number of open apps, but the price is a lower performance.
So you're probably just meaning multitasking performance.
Click to expand...
Click to collapse
I, again , partially agree, i was fundamentally talking about multitasking performance. And sure, zram takes cpu cycles... I reserved a full, standalone point to say that.
But
i wouldn't be so sure about one being better than the other. My arguments are in the original post.
As I wrote above zRAM is way faster than swap. So zRAM should be the first choice if you're running into low RAM situations.
If you still need more go and enable swap as well.
Click to expand...
Click to collapse
As I wrote, and argumented, before, compcache/zram is way faster in a way limited range of situations.
Last but not least:
Why are you talking about compache all the time? It's called zram nowadays, so call it that way.
Click to expand...
Click to collapse
Because
1) I'm an old cat.
2) "Compcache" is a well chosen autodescriptive term.
3) It's been "compcache" for over 4/5 of it's life, and, well...
4) I'm an old cat. ;D
Have fun, and thanks for all your work in O2x developing.