[Q] Would enabling swap boost real world performance? - HTC Incredible S

I'm interested in any real world experiences of people using a swap partition on the SD card or similar solutions. I mostly see guides about how you enable swap, which isn't that hard, but any quantifiable or subjective reports of improved performance is lacking.
My only experience using swap was using an openwrt router (with very limited resources) where it was vital for some stuff to function at all, but I couldn't see any general speed improvements, and when swap was used it was terribly slow.
Do you use swap or tried it, does it help? How much?

PremiumMediocre said:
Do you use swap or tried it, does it help? How much?
Click to expand...
Click to collapse
Apparently this is not something that interest people, but in case someone searches for swap and finds this post I can say it definitely helps with multitasking. Currently my phone uses over 100MB of swap space, and lags due to apps being terminated due to low memory is a more rare occurrence nowadays.

Just some interesting reading about this:
http://zerocredibility.wordpress.com/2009/08/24/why-android-swap-doesnt-make-sense/
http://android.stackexchange.com/questions/2310/how-will-a-swap-partition-file-affect-the-system
If you're still interested, read these two links. A bit old though, but the only difference might be that Google has put an effort into making Android's way of freeing memory better. In that case, from what they say, I'd say there's a chance that swap will increase your performance.

Thank you, I've been reading up on swap as well, and it's not completely clear cut.
From your first link the argument:
"Having swap actually prevents the native Android memory management scheme from activating. The system sees memory and doesn't distinguish between physical and virtual. It will therefore prefer swap over the native Android memory management scheme, and won’t activate the native scheme until swap is full."
I believe this is just plain inaccurate. Even if you set swappiness to 100 android will terminate apps without filling the swap space, and swap is never treated as plain ram as far as I know.
Some real benchmarks is sourly needed though.

PremiumMediocre said:
Thank you, I've been reading up on swap as well, and it's not completely clear cut.
From your first link the argument:
"Having swap actually prevents the native Android memory management scheme from activating. The system sees memory and doesn't distinguish between physical and virtual. It will therefore prefer swap over the native Android memory management scheme, and won’t activate the native scheme until swap is full."
I believe this is just plain inaccurate. Even if you set swappiness to 100 android will terminate apps without filling the swap space, and swap is never treated as plain ram as far as I know.
Some real benchmarks is sourly needed though.
Click to expand...
Click to collapse
I tried to find done benchmarks, but it seems like there are none...
And like I said, old links so Google might have done something about the issues they're talking about
Sent from my Incredible S using xda app-developers app

Also have a look in the desire Z section for this. They only have 512mb ram (we have 768) so they are always looking for ways to free up ram
There is a lot of discussion about swap so have a look there They might know a lot more compared with us

markj338 said:
Also have a look in the desire Z section for this. They only have 512mb ram (we have 768) so they are always looking for ways to free up ram
There is a lot of discussion about swap so have a look there They might know a lot more compared with us
Click to expand...
Click to collapse
I think the speed of the processor is also important in this context since the native way to save memory is letting programs recreate the last state they were in before they were shut down. A fast processor would make swap less attractive.
In case you anyone wants to try, I'm using the Hunterwu kernel and used swapper 2 to activate the swap partition. The only hang up setting it up was that swapper 2 identified the wrong partition as swap but that could be manually changed.

PremiumMediocre said:
I think the speed of the processor is also important in this context since the native way to save memory is letting programs recreate the last state they were in before they were shut down. A fast processor would make swap less attractive.
In case you anyone wants to try, I'm using the Hunterwu kernel and used swapper 2 to activate the swap partition. The only hang up setting it up was that swapper 2 identified the wrong partition as swap but that could be manually changed.
Click to expand...
Click to collapse
Tell us if its any better, I might do the same

Related

Getting Android to USE swap (Cyanogen 5.0.7) 32B

I know this is as beaten as a dead horse, but I have to ask it anyways.
I've setup both Compcache and a swap partition on my Class 6 SD card, but I'm finding myself endlessly frustrated by the fact that Android is still killing stuff after just dipping it's toes in the swap.
Someone at HTC should be shot for making these phones with this little memory.
I'm aware the performance may be terrible and it may (will) murder my SD card, but how can I force Android to see all of the memory space as available?
As far as Linux is concerned there's 52MB of free memory (Meaning Android hasn't allocated it at all), including 16MB of physical swap that hasn't been touched (of 16MB). Android's still killing stuff (like my terminal session).
I'm aware that Android's management is supposedly more elegant, but I'm finding many apps and programs don't properly save their state and don't restore seamlessly, and I tend to multitask a lot and, well, this isn't working well. I at least want to see what a swap-heavy setup runs like, but Android won't let me!
There is a search button. There are plenty of howto's.
Hint: userinit.sh
-------------------------------------
Sent via the XDA Tapatalk App

Using NAND as RAM?

After many tests I think that we really suffer from a lack of RAM. But the internal memory (NAND) should be the same speed as RAM I think. So why we don't use another 128Mb of NAND as additional RAM? A sort of swap part, but used as RAM and not as normal swap....
If someone related to the kernel would answer is it possible or not, it would be good)
DiMiK said:
After many tests I think that we really suffer from a lack of RAM. But the internal memory (NAND) should be the same speed as RAM I think. So why we don't use another 128Mb of NAND as additional RAM? A sort of swap part, but used as RAM and not as normal swap....
If someone related to the kernel would answer is it possible or not, it would be good)
Click to expand...
Click to collapse
Using it as RAM would propably require major changes to the kernel if it is even possible which I doubt it is. Using it as swap would be the possible alternative and I pretty sure that is very possible and would help performance but at a cost.
1. You would either have very little left for system and data or you would have to put system and/or data on the SD-card and that alone may make you lose anything you gain from putting swap on NAND.
2. I actually asked the swap-on nand question myself and well, we can't replace our NAND, at least not easily and swap is I/O intensive and intesive I/O will sooner or later wear out the NAND. So basicly this is not a good alternative unless you want to turn your phone into a paperweight sooner than you had planned.
So what we can do is using compcache and/or swap on SD-card. The easiest thing is to just enable some compcache. It uses RAM as swap and uses compression on the contents so we can hold more things in RAM that we would usually be able to. This means Android can keep more apps in "sleep" allowing for faster switching between apps but it will also decrease the possible amount of available RAM for the active app. I usually turn on compcache with the default setting which is to use 25% of the RAM for compressed swap. It might be placebo but IMHO it feels a it "smoother" to use after that.
Another alternative is to use a swap partition in the sdcard. Just using swap means you do not need to load any compcache kernel modules and there is no compression taking place so it's a good alterantive. However you need know your way around partitioning SD-cards to get this running so it's not as easy as just enabling compcache (assuming the build supports compcache).
For the really advanced you can enable compcache with backing swap. It means it uses a certain amount of compressed swap i RAM and when it runs out of space there it starts putting stuff on the SD-card swap partition. Once again, a bit tricky to setup but may be the best alternative.
Read more about it here: http://wiki.cyanogenmod.com/index.php/Compcache
kallt_kaffe said:
I usually turn on compcache with the default setting which is to use 25% of the RAM for compressed swap. It might be placebo but IMHO it feels a it "smoother" to use after that.
Click to expand...
Click to collapse
It make good effect: more applications can run simultaneously.

Making g1 run faster? (10 mb hack)

Hi, I was wondering if I can use the 10 mb ram hack with my g1 with CM 6.0 RC2. I noticed most of the tutoriials are using 4.xx.xx so I wanted to ask before I do it. My phone is kind of slow even though it is overclocked at 576mhz and 64 mb class 6 memory swap. Thanks.
Ties0 said:
Hi, I was wondering if I can use the 10 mb ram hack with my g1 with CM 6.0 RC2. I noticed most of the tutoriials are using 4.xx.xx so I wanted to ask before I do it. My phone is kind of slow even though it is overclocked at 576mhz and 64 mb class 6 memory swap. Thanks.
Click to expand...
Click to collapse
There is no 10 mb hack and won't be. It is not possible with Froyo.
As indicated above there is no 10mb hack and there never will be.
I am currently using the latest nightly and it is super fast and stable. As fast as donut (no ****).
3D Gallery works perfectly and there have been a bunch of small cool features added to the nightly.
I highly recommend it.
Awesome work has been done by Cyanogen and Crew.
ok thanks for the reply guys. Is there any other way to make my rom faster? Thanks.
Ties0 said:
ok thanks for the reply guys. Is there any other way to make my rom faster? Thanks.
Click to expand...
Click to collapse
Of course reduce or remove swap,
android has it's own swap mechanism that causes little ram to actually be least recently used, thus if swap is enabled the phone will be constantly swapping it in/out!
In addition to reducing the life of the SD card its slow. I understand a very little bit of swap *may* allow some edge cases where a *little* more ram is needed or to offload something like launcher that may be configured to stay in ram to work faster.. however you can't forget the speed issue.
Try this enter console on your phone and run:
dd if=/dev/zero of=/sdcard/swapspeedtest bs=1048576 of=64
Note the time it takes, that is the time to write 64mb on a swap out operation.. if it seems too long to wait for a task its too much swap. 12mb is almost acceptable. I just stick to comp cache only. . Upped it from the default 12 to 15 MB since I had one or two tasks that just needed a tad more memory to play nice.
Also what is slow, returning to home? A particular app? I doubt its everything, usually its launcher and there are ways of locking it in home, upgrades to awd, and alternative launchers. These may help.
ezterry said:
Of course reduce or remove swap,
android has it's own swap mechanism that causes little ram to actually be least used, thus if swap is enabled the phone will be constantly swapping it in/out
In addition to reducing the life of the SD card its slow. I understand a very little bit of swap to allow some edge cases where a little more ram is needed or to offload something like launcher that may be configured to stay in ram.. however you can't forget the speed issue.
Try this enter console on your phone and run:
dd if=/dev/zero of=/sdcard/swapspeedtest bs=1048576 of=64
Note the time it takes, that is the time to write 64mb on a swap out operation.. if it seems too long to wait for a task its too much swap. 12mb is almost acceptable. I just stick to comp cache only. . Upped it from the default 12 to 15 MB since I had one or two tasks that just needed a tad more memory yo play nice.
Also what is slow, returning to home? A particular app? I doubt its everything, usually its launcher and there are ways of locking it in home, upgrades to awd, and alternative launchers. These may help.
Click to expand...
Click to collapse
Thanks for the detailed response! I will try lowering the swap partition, I always thought it would be fast because of the class 6 speeds. Does putting all my apps on SD make it slow as well? Also, returning to home is the main lag I'm talking about as it takes quite a while to see my apps. Thank you!
ezterry said:
Of course reduce or remove swap,
android has it's own swap mechanism that causes little ram to actually be least used, thus if swap is enabled the phone will be constantly swapping it in/out
In addition to reducing the life of the SD card its slow. I understand a very little bit of swap to allow some edge cases where a little more ram is needed or to offload something like launcher that may be configured to stay in ram.. however you can't forget the speed issue.
Try this enter console on your phone and run:
dd if=/dev/zero of=/sdcard/swapspeedtest bs=1048576 of=64
Note the time it takes, that is the time to write 64mb on a swap out operation.. if it seems too long to wait for a task its too much swap. 12mb is almost acceptable. I just stick to comp cache only. . Upped it from the default 12 to 15 MB since I had one or two tasks that just needed a tad more memory yo play nice.
Also what is slow, returning to home? A particular app? I doubt its everything, usually its launcher and there are ways of locking it in home, upgrades to awd, and alternative launchers. These may help.
Click to expand...
Click to collapse
I have about 3-5 apps that I would like to be running at one time? Should I be using CompCache or Swap? Currently I am on SuperD 1.9.3 WGK. I have been reluctant to run Froyo roms because they are so much more memory hungry in my experiences. My current rom runs pretty fast with a 96mb swap. If I were to fun a Froyo rom, what can I do to be able to run the 3-5 apps and retain speed?
Ties0 said:
Thanks for the detailed response! I will try lowering the swap partition, I always thought it would be fast because of the class 6 speeds. Does putting all my apps on SD make it slow as well? Also, returning to home is the main lag I'm talking about as it takes quite a while to see my apps. Thank you!
Click to expand...
Click to collapse
If you are using BOTH SWAP & have applications installed to the sdcard, then it will ****REALLY**** be slow.
With just applications on the sdcard, your speed should be fine.
Ties0 said:
Also, returning to home is the main lag I'm talking about as it takes quite a while to see my apps. Thank you!
Click to expand...
Click to collapse
This is a symptom of launcher being evicted from ram, try the stay in ram option in settings->adw launcher->system settings->system persistent in the more recent versions of adequate (I think included with rc2 if my memory serves me)
It may not be perfect as it will still get killed if a very large application is loaded.
Either you need a launcher that behaves as a good android application, and can quickly reload it's last state, even if it was not in ram when you requested it.. or launcher needs to be considered outside the usual android memory management and to be kept in ram.
These persistent processes are where you may depending on your usage of the phone find comp cache or swap in low amounts (32mb combined is probably the absolute max) may help as they will have allocated ram that is rarely used and not automatically freed as they are persistent..
ezterry said:
This is a symptom of launcher being evicted from ram, try the stay in ram option in settings->adw launcher->system settings->system persistent in the more recent versions of adequate (I think included with rc2 if my memory serves me)
It may not be perfect as it will still get killed if a very large application is loaded.
Either you need a launcher that behaves as a good android application, and can quickly reload it's last state, even if it was not in ram when you requested it.. or launcher needs to be considered outside the usual android memory management and to be kept in ram.
These persistent processes are where you may depending on your usage of the phone find comp cache or swap in low amounts (32mb combined is probably the absolute max) may help as they will have allocated ram that is rarely used and not automatically freed as they are persistent..
Click to expand...
Click to collapse
Thanks for the detailed response! I just changed the adw launcher and deleted my swap partition... It seems to be much slower when pressing home (icons are taking a while to load) so I might just use 32 mb for swap.
EDIT: question, what exactly does ext4 do? I know swap is like external ram, but what does ext4/ext3/etc exactly do? and how much should I put in? I tried googling but could not find the answer. Thanks!
Ties0 said:
EDIT: question, what exactly does ext4 do? I know swap is like external ram, but what does ext4/ext3/etc exactly do? and how much should I put in? I tried googling but could not find the answer. Thanks!
Click to expand...
Click to collapse
On CM6, nothing. On CM 4 & 5, it was used for Apps2Ext (formerly known as Apps2SD - before Google came out with their own flavor). However, CM6 does not have Apps2Ext. It has been indicated that it will be targeted for 6.1.

Swap partition for SGS ?

Hi again guys...
In Linux we have a SWAP partition for some time if RAM (Random Access Memory) will full OR for speed up applications by buffering in swap partition.
(Recommend Linux SWAP partition size: half of RAM)
so Android is Linux based and have kernel like Linux. Is it work to make a SWAP partition for SGS with swap file system?
You don't want that...
Android doesn't wipe RAM immediately anyway, so apps which are open and shutdown can be restarted again quickly (unless the RAM has been reused).
Also, apps on Android are designed to be shut down whenever free RAM runs out (its in the development guidelines that all applications should expect to be shut down at any time). Since most Android phones use high-speed NAND memory, when properly configured, apps load quicker too
The problem with swap is that it can lead to thrashing and loss of battery life. It's good for computers (because generally, you would rather lose performance and ensure you don't lose work), but on Android, applications should be killable at any time, and should have mechanisms to protect their work anyway.
It's probably possible to create a swap partition/file if you wish (try to swapon), but I foresee some potential side-effects, especially if you don't want to spend a lot of time managing memory manually.
i didn't think about battery life.
Thank you so muchhhhhhhhhh
I was actually exploring this option last night and stumbled that the kernel does allows swapon commands. I remembered trying it earlier on a stock rom but it was not available then.
Why I need the swap was because of the frequent shutdown of my launcher pro due to apps contenting for memory. The live wallpaper and heavy Widgets like pure messenger pro aren't helping much either, after much usage the device just slows down, lags and silently kills the background apps. The "minfree" settings were also tweaked but with much less desirable results was seen...
So I downloaded an app called "swapper2" from market and tested via 2 methods; Swap file and swap partition.
The performance of a swap file that sits in the NAND is not really that great. In fact it kinda lags me when memory is being swapped in and out of it. I think its the same problem with the i/o lag problems with any other rom
Then I tried a swap partition on my class 6 SD card. Although the lifespan of the card would be shortened and the battery life would be impacted, the performance is better compared to the earlier method.
In either method, the amont of apps that can be left opened at the foreground and background had increased and doesn't lag as more apps is being launched. Not bad for me but well, I guess it's all up to the user of the device at the end. Just my 2 cents...
I'll try the swap file method again over at the ext2 partition created by the lagfix and see how it goes next. Not sure if anyone interested though...
Sent from my GT-I9000 using XDA App
It seems that using the swap partition doesn't have the lag compared to using the swap file method.
It may be due to the I/O of multiple storage (parallelism ?) is better than a single storage or writing into the raw partition is better in terms of performance than a swap file.
I'm done with my findings, the device still have 60mb free and never lags, I'm sold.
Sent from my GT-I9000 using XDA App

512Mb RAM - Getting it out ?

I have a Flash application that requires ~130Mb of RAM and I want to run it on my Galaxy S
I've installed Froyo JPK with latest flash 10.1, but just before the end of startup procedure I always get the "exclamation circle" icon which is apparently the "out-of-memory" message in flash.
I have tried to free up the memory with task killers and memory boster, but can't get it above 175 Mb, which is obviously still not enough, since probably browser and other applications/services use it back before the flash application starts completely. Or might be also some limitation my browser in Galaxy S ? -> see EDIT below
On HTC Desire this same application works like a charm.
So I wonder...
Is there any way to get more free memory ? [EDIT: Yes, with "Chuck Norris mode" app killers, but i does not always help and it's lame]
Is there any way to get more than 311-322Mb RAM used for Applications ? [EDIT: Yes, when developpers will found out the way how to get less memory used for video codecs or even found the misterious 32Mb which are yet nowhere to be found]
Can we expect to this memory issue to be solved in future Froyo releases ? [probably only Samsung knows that, but for now it seems very unlikely]
EDIT: Found out that I get out-of-memory with every single application when it reaches 128Mb of RAM usage.
This is again specific to SGS. Looks like this is some internal max memory allocation size per application/VM
So here is another question:
Is there any way to increase this limit (might be android internal or dalvik VM related)?
no
no
no
sorry to say that...
flypubec said:
I have a Flash application that requires ~130Mb of RAM and I want to run it on my Galaxy S
I've installed Froyo JPK with latest flash 10.1, but just before the end of startup procedure I always get the "exclamation circle" icon which is apparently the "out-of-memory" message in flash.
I have tried to free up the memory with task killers and memory boster, but can't get it above 175 Mb, which is obviously still not enough, since probably browser and other applications/services use it back before the flash application starts completely. Or might be also some limitation my browser in Galaxy S ?
On HTC Desire this same application works like a charm.
So I wonder...
Is there any way to get more free memory ?
Is there any way to get more than 309Mb RAM used for Applications ?
Can we expect to this memory issue to be solved in future Froyo releases ?
Click to expand...
Click to collapse
If you need that amount of memory you should use a computer.
Its not the phone thats the probem here. its what you try to run.
//Damian
I would personally put up money to get the RAM issue resolved.
People keep saying that 324~ MB is enough. That's not the point though. The point is that Samsung advertised 512MB. Any reasonable person would assume that, like other phones containing 512MB of RAM, that the phone would have 400+MB available for general usage. 324 MB for such a power phone is dismal. I consider Samsung's claim to be a form of false advertising. Yes, technically the phone has 512MB of RAM, but not according to the reasonable expectations of a consumer. Almost half of the stated RAM isn't usable to the end user for applications. This is a problem with the phone from the standpoint of delivering the expected value to the consumer.
Dear XDA Developer Legends,
Do you think it is possible that you will be able to free up ram that is allocated to the ram disk?
Yours,
Concerned Customers
Hm, maybe its applicable for a lawsuit?
andars05 said:
I would personally put up money to get the RAM issue resolved.
People keep saying that 324~ MB is enough. That's not the point though. The point is that Samsung advertised 512MB. Any reasonable person would assume that, like other phones containing 512MB of RAM, that the phone would have 400+MB available for general usage. 324 MB for such a power phone is dismal. I consider Samsung's claim to be a form of false advertising. Yes, technically the phone has 512MB of RAM, but not according to the reasonable expectations of a consumer. Almost half of the stated RAM isn't usable to the end user for applications. This is a problem with the phone from the standpoint of delivering the expected value to the consumer.
Click to expand...
Click to collapse
the phone has 512MB and you can use all. But the system use some of it.
Its only user that cant read and understand how it work hat keep asking about it.
And this phone has more ram that most have. So yes it is enough of ram.
'If you try to runt 50+ all time you will and up with low memory.
But its the same on a computer. none complain about that.
Only that you can only see 3.5GB on windows and use that on a 32.bit system. Well now you can see 4GB and all people are happy.. but they still cant use it, but its looks good.
That the same with this phone.
If samsung did show 512MB and did show how much that was free, all people that complain would be happy. but it dont change a bit what thay can use.
yaocheng said:
no
no
no
sorry to say that...
Click to expand...
Click to collapse
That make no sense
there is no reason to get less memory with the i9000 when comparable devices like the nexus one running the same OS version has 100mb+ more free ram
DamianGto said:
the phone has 512MB and you can use all. But the system use some of it.
Its only user that cant read and understand how it work hat keep asking about it.
And this phone has more ram that most have. So yes it is enough of ram.
'If you try to runt 50+ all time you will and up with low memory.
But its the same on a computer. none complain about that.
Only that you can only see 3.5GB on windows and use that on a 32.bit system. Well now you can see 4GB and all people are happy.. but they still cant use it, but its looks good.
That the same with this phone.
If samsung did show 512MB and did show how much that was free, all people that complain would be happy. but it dont change a bit what thay can use.
Click to expand...
Click to collapse
This misses the point of my original statement. The Nexus One is advertised (along with many other phones) as having 512MB of RAM. The N1 has 380-400+MB available of RAM available for applications, as do many other phones containing 512MB of RAM.
Yes, the system does reserve some for certain system functions. Even after those functions have been reserved on other 512MB models, the vast majority is still available to the end user. This is not the case on the Galaxy S series. This is evident by the original posters comment regarding his application.
To address your Windows example: Windows 32 bit actually states that only a portion of the 4GB is available for use. I don't see in the advertisements where Samsung states "Contains 512MB -- 324MB available for actual usage"
I think most consumers, like myself, would assume that the amount of RAM advertised is directly correlated to the amount usable for applications.
Otherwise, what's the difference between a phone advertised as having 384MB and the Galaxy S? They both could have the same amount of RAM available.
andars05 said:
Windows 32 bit actually states that only a portion of the 4GB is available for use.
Click to expand...
Click to collapse
But its not the case here.
+1 for the rest.
This is what i get if I run top command from adb from a freshly booted phone:
←[H←[JMem: 296300K used, 15048K free, 0K shrd, 6968K buff, 134720K cached
CPU: 1.3% usr 2.3% sys 0.0% nic 96.2% idle 0.0% io 0.0% irq 0.0% sirq
Load average: 0.99 1.33 0.59 1/351 3109
Wonder what this "cached" means.
Can somebody pls run this on HTC desire ?
I don't think our phone has 512mb of RAM physically available to the system. I think the phone has 512mb of RAM in total but it looks like 128mb of it is graphics RAM or something. Meaning we only have 384mb available to the system. The maximum amount of RAM I can ever get free is about 175mb so I don't think that it's reasonable that the system is using about 337mb of RAM. My desktop linux system uses less RAM than that on boot.
Isn't the memory allocation for graphics dynamic?
how often does the graphics really need all that ram?
any why aren't other devices affected by this? (doesn't the GPU on nexus or milestone for example need memory allocated?)
sionyboy said:
Do you think it is possible that you will be able to free up ram that is allocated to the ram disk?
Click to expand...
Click to collapse
Please explain. Which ram disk do you mean?
Also, since it runs on linux, cant we assign some space from the internal sd (or external) to make a virtual ram disk that would be used as ram when needed? some king a paging file that we know on windows...
And if this is possible, can we assign it to video so graphism will be a little slower but app will become faster?
I think there is something we can do if we can change assignation of ram, apps, and video to make this phone way much powerful.
(just an idea...)
franklin01 said:
Also, since it runs on linux, cant we assign some space from the internal sd (or external) to make a virtual ram disk that would be used as ram when needed? some king a paging file that we know on windows...
And if this is possible, can we assign it to video so graphism will be a little slower but app will become faster?
I think there is something we can do if we can change assignation of ram, apps, and video to make this phone way much powerful.
(just an idea...)
Click to expand...
Click to collapse
There's always Compcache..that worked like a charm on the G1 and Magic.
http://forum.xda-developers.com/showthread.php?t=724960
As you can see, all other Android phones reserve some memory to the system... It's just the way it is.
the sgs kernel creates amemory blackhole, that is, it starts using memory after a certain memory address.
It does that because many things in the hardware are using fixed memory addresses to allocate their own memory which is not managed by the kernel itself and the kernel will never touch or see it.
what you call "system memory" is usually memory used and seen by the kernel, for the OS's functionality: various applications, services, daemons, kernel daemons, kernel memory itself (its not much) and some time some ramdisks.
Every phone also uses that of course, which amounts for like 80-130megs. They also often use small black holes of like a couple of megs, but that's so little that no one will notice.
The sgs makes a big blackhole. To me it's more of a design fault, but not much you can do about it I guess. It would need someone who's going to read the complete hardware sheets to bypass that, if at all possible, lol. Or samsung.
I bet they fixed the design issue in the galaxy tab and either the chip has separate dedicated memory either there's no blackhole.
Another theory why the blackhole is necessary is that there's a bug in the chip and it's messing up a portion of the memory, so this portion is left unused (blackhole'd - never seen by the kernel) for stability reasons.
i hope this gives some insight.
reference from the previously linked post:
- Galaxy S [2.1] RAM = 512 MiB | Linux = 325 MiB | Reserved = 187 MiB (with I9000XWJM2 firmware)
notice the huge black hole here (187 megs)
I used to have more than 300mb free after reboot with nexus one...
DamianGto said:
the phone has 512MB and you can use all. But the system use some of it.
Its only user that cant read and understand how it work hat keep asking about it.
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No, *we* can't use it all , because we != system. The debate is not whether or not there is 512MB of physical memory; there could be , since Samsung advertises as having 512MB, but its not all user accessible memory. We don't know for what the system is utilizing that memory, I don't think its for loading some of the core system components; otherwise we should be left with more free RAM like other devices with 512MB of RAM (i.e Nexus One). Its more likely that 188MB is used by either the GPU and other hardware or as a Ram disk.
In contrast, other phones having 512MB of RAM don't use user allocated memory for system or hardware use (at least not the same way Samsung does). They are somehow handling it differently, maybe their GPU's and Other hardware software counterparts have dedicated memory. Whatever said, at the end of the day in the user's point of view, Galaxy S DOES NOT have 512MB of RAM as what we were all led to believe . That is pure deception !!
If they knew this was the case then they should have alerted this to the users. For-example a spec sheet for Samsung Fascinates says 512MB Flash/384MB RAM they should have advertised Galaxy S like that instead of lying through their teeth.

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