[TWEAK][APK][CWM] [update2.0.0] Seeder entropy generator to provide lag reduction

Hey everyone,

So, I was experiencing significant lag as we all do from time to time, and decided I was going to get to the bottom of it.

After tracing and debugging for hours, I discovered the source of 90% of Android's lag. In a word, entropy (or lack thereof).

Google's JVM, like Sun's, reads from /dev/random. For all random data. Yes, the /dev/random that uses a very limited entropy pool.

Random data is used for all kinds of stuff.. UUID generation, session keys, SSL.. when we run out of entropy, the process blocks. That manifests itself as lag. The process cannot continue until the kernel generates more high quality random data.

So, I cross-compiled rngd, and used it to feed /dev/urandom into /dev/random at 1 second intervals.

Result? I have never used an Android device this fast.

It is literally five times faster in many cases. Chrome, maps, and other heavy applications load in about 1/2 a second, and map tiles populate as fast as I can scroll. Task switching is instantaneous. You know how sometimes when you hit the home button, it takes 5-10 seconds for the home screen to repopulate? Yeah. Blocking on read of /dev/random. Problem solved. But don't take my word for it .. give it a shot!

Update!
I've built a very simple Android app that bundles the binary, and starts/stops the service (on boot if selected). I'll be adding more instrumentation, but for now, give it a shot! This APK does not modify /system in any way, so should be perfectly safe.

This is my first userspace Android app, so bear with me!

Note that this APK is actually compatible with all Android versions, and all (armel) devices. It's not at all specific to the Captivate Glide.

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Ryuinferno said:

Before doing anything, please read the first post of this thread to understand how this thing functions!
Read it here: First post

First things first I am not the OP but things need to be sorted out...Ok...this thread is starting to get more and more attention, which is good because with more people to test things out, the more feedbacks and the more improvements can be done...however, the thread is now cluttered by tons on unhelpful posts, like "how to use this", "do I need root" etc...useful posts get pushed wayyy behind, until it is hard for people who are really trying to discuss to keep track...so I am here to answer the basic questions:

Do you need root for the app?:
Yes

Can it work on xxx device?:
Yes, as long as your device is arm based

Where to download the app?:
Here: http://xdaforums.com/attachment.php?attachmentid=1640660&d=1358063993
Or search Play Store for a donate version...
The other 2 attachments are the rngd binary and a diff patch, which are not really required for end users...

How do I know that it is working?
Prior to starting seeder entropy generator through the app (v1.2.4 onwards), the bar below will only show numbers around 100-200++. After you start it, if the bar fills up and the value shoots up to 4000++, then it is working.

Do I have a risk of bricking my device?
No because the app won't modify system files at all...anything just uninstall...
For the zip, it only adds files to your system partition...does not modify any, so if you want to stop using this, you can disable it via the extended menu script...

It does not do anything/It is placebo/I see no improvements/It is awesome!/Wow!:
Well, this is not constructive or helpful...NOT AT ALL...keep in mind that this is still a WIP...research and discussions are still going on...if it is not working or you feel no change or a great improvement, please describe more and explain...which a lot of others are already doing so......keep it up!

Seems that certain people are so bugged by the app...so...for those who prefer to run this via a script and init.d, read on...(the script works the same as the app, but with a few extra features)


=======================================================================================================================
UPDATE: Seeder_v7 is out, as suggested by pepoluan, it now detects for qrngd (built in rngd for Qualcomm Snapdragon-based devices), if it is there, then it will not start as rngd may conflict with it...the rngd binary is also using the latest version (it is turned off when screen is off)...users of previous versions can just flash it over...

INSTALLING
You need init.d support for this!
Download and flash:

http://www.androidfilehost.com/?fid=9390248398092764755

How to use this script?:
After flashing, launch terminal emulator and type

Code:

su
seeder

You will get a menu like this:

NOTE: There will be NO app after flashing! This only installs the necessary binaries and scripts...


For those who cannot install via recovery:
You get a status 0 error -> replace the update-binary in Seeder_v6.zip with one from another zip that works with your device

OR

Use the new installation method!

Instructions:
1. Download Seeder_v7_non-CWM.zip from here:

http://www.androidfilehost.com/?fid=9390248398092764756

2. Extract the zip, you will get a folder named "install"
3. Place the folder in the root of your sdcard (/sdcard)
4. Launch terminal emulator, type:

Code:

su
cd /sdcard/install
sh install.sh

5. Ignore any error messages (those are only warnings, only happens to current users)
6. You are done! The script will auto-delete the "install" folder as it is not required anymore...

Sample output:

UNINSTALLING:
And now for the way to clean up Seeder_7:
Via recovery:
Flash Seeder_v6&7_Uninstall.zip:

http://www.androidfilehost.com/?fid=9390248398092764753

Via terminal:
1. Download Seeder_v6&7_Uninstall_non-CWM.zip:

http://www.androidfilehost.com/?fid=9390248398092764145

2. Extract it to the root of your sdcard (/sdcard), you should get a file named uninstall.sh
3. Launch terminal emulator and type this:

Code:

su
cd /sdcard
sh uninstall.sh

4. You are done! Everything gets cleaned up, including uninstall.sh...

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Adinaky said:

This sounds nice, but can you make some clean instructions for everybody to understand?

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entro

Metallice said:

10 grand... for nothing but snake oil...

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zeppelinrox said:

So I did a bit of digging and a bit of research and a bit of testing.
I really dunno if the tweak makes that big of an effect but I did discover a nice trick to have a nice fat entropy_avail with zero overhead.

One of the first pages I skimmed was http://linux.die.net/man/4/random which mentioned at the bottom these other files:
read_wakeup_threshold contains the number of bits of entropy required for waking up processes that sleep waiting for entropy from /dev/random.
write_wakeup_threshold contains the number of bits of entropy below which we wake up processes that do a select() or poll() for write access to /dev/random.

Normally, read_wakeup_threshold is 64 and write_wakeup_threshold is 128

I also wondered why most users report that their entropy_avail was by default in the 200ish range while mine was always by default over 300.

I had also found this page at linuxinsight. I had used that site alot when researching Kick Ass Kernelizer's sysctl tweaks.

So I thought, hey I wonder if I can use sysctl to set good values and low and behold, I looked in my script and I already have settings for both lol:

Code:

busybox sysctl -e -w kernel.random.read_wakeup_threshold=128;
busybox sysctl -e -w kernel.random.write_wakeup_threshold=256;

As you can see, I had doubled the default values - and that's why my entropy_avail was always over 300.

So I decided to mess with sysctl a bit.

Connected the phone to the laptop.
In one command prompt I watched the entropy_avail with this one liner:

Code:

while :; do cat /proc/sys/kernel/random/entropy_avail; sleep 1;done

In a second command prompt I did the sysctl thing...
I found that write_wakeup_threshold didn't effect entropy_avail at all.

But read_wakeup_threshold is a totally different story

I did

Code:

busybox sysctl -w kernel.random.read_wakeup_threshold=2048

The entropy_avail just started climbing....

All the way up to 3600+ and just stayed there. Never went down at all.
Actually, the more I did stuff with the phone, the faster the level would climb.

So it would never go down and would never get used.
I thought well maybe I should lower it so it does get used.
I kept lowering read_wakeup_threshold until it got down to 1200 and finally entropy_avail dropped to 2400+ and kept climbing until 3600 and then would drop to 2400 immediately and up again and so on...

I played with different values.
Setting it to 1000... entropy would go up to 3000 and then drop to 2000 and up to 3000 again....
Setting to 750.... entropy would go up to 2250 and drop to 1500 and up to 2250 again...

So the pattern is:
max entropy_avail=read_wakeup_threshold * 3
min. entropy_avail=read_wakeup_threshold * 2 (ie. read_wakeup_threshold * 3 - read_wakeup_threshold)

So it builds up 3 times the read_wakeup_threshold and then when it hits that limit, it drops the value of read_wakeup_threshold.

If you want to lock it it at the highest possible value (4096), you'd do:

Code:

echo 1366 > /proc/sys/kernel/random/read_wakeup_threshold

Or

Code:

busybox sysctl -w kernel.random.read_wakeup_threshold=1366

You can add either of those to any init.d script.
However, on my device, it won't go over 3600 so you can test for yourself how high yours will go.
If all you can get is 3600ish just go with 1200 (ie. 3600/3)

In Kick Ass Kernelizer I'm gonna make it like so:

Code:

busybox sysctl -e -w kernel.random.read_wakeup_threshold=1024;
busybox sysctl -e -w kernel.random.write_wakeup_threshold=2048;

That will make it bounce between 3072 max and 2048 min.
I'm making write_wakeup_threshold twice the amount of read_wakeup_threshold simply because that's what it is by default.

But hey, maybe I can save battery life if I make it 1280 just so it stays locked in at 3600+ and it doesn't have to keep rebuilding entropy_avail lol

So conclusion is: since there is a definite pattern on how entropy was being built up to a pre-determined level and dropped to a pre-determined level, it wasn't actually being used. That's just how it's programmed.

If the setting isn't there to "hold" all the entropy, it just drops/flushes it and force feeding it entropy won't make it not spit it out

So at least I found the setting that will make it hold it in lol

Maybe somebody would like to give it a try and test to see if it actually saves battery by setting read_wakeup_threshold to 1366.

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