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!
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.
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?:
Can it work on xxx device?:
Yes, as long as your device is arm based
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...
You need init.d support for this!
Download and flash:
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:
4. You are done! Everything gets cleaned up, including uninstall.sh...
There has been a lot of controversy about Seeder/rngd. In newer versions of Dalvik, nothing touches /dev/random, and yet many users (including myself) still notice a lag reduction. There are theories ranging from kernel lock contention to UI polling load when crediting the entropy pool to simply kicking the governor. And many who believe it's all placebo. I'm trying my best to figure out what exactly is happening, and others are as well.
Someone asked how I arrived at the conclusion I did when I started the thread back in November, and I posted this; I think it might be better served here:
A while back one of the webapps I was hosting on Tomcat (server-side) was experiencing some inexplicable latency and while stracing java I saw it frequently hanging on read()'s from /dev/random. I checked the available entropy, and it was constantly under 250 or so. It was a VM, no HWRNG, so I decided to use rngd to push urandom->random.
Dropped session creation times under load from 5-10 seconds to less than a second.
It's worth noting that Linux is one of very few OSes that have a blocking RNG device. Free/OpenBSD, Windows, etc.. essentially only provide urandom. It's generally considered secure, even for long-term crypto keys, so long as the initial seed is big (and random) enough.
Checked on my device, and saw a few processes grabbing /dev/random. /proc/sys/kernel/random/entropy_avail reporting depleted input pool. Figured it was worth a shot, so I rebuilt rngd for arm (with a few patches, linked on first page), and tried it out. It made a significant difference. Posted it up on this thread, and had a lot of positive feedback. Wanted to get into Android development, so figured.. why not wrap a little UI around it. More positive feedback, so I threw it on the market as well.
I had no idea it would take off like this and was shocked when I saw it Thursday morning. I'm in the awkward position now of explaining why it seems to work for some people, and not for others, especially given the fact Dalvik doesn't have references to /dev/random as of ICS. Theories abound, but it looks like it might be an issue of polling the UI for input events when the entropy pool drops (which never happens so long as rngd is running).
I'm doing this as a hobby. I'm a *nix admin by trade, and can only spend time working on this stuff on evenings and weekends, and the last few weeks have been kinda nuts.
I want to stress to everyone that:
a) It doesn't work the way I thought it did on later Android builds, but it does reduce latency for me and many others even on these builds,
b) I'm offering (and always will offer) Seeder for free to everyone on XDA,
c) Like I say in the market description, if anyone has purchased it and it isn't working, PLEASE email me for a refund (and let me know what device you're on if you're willing).
I was one of the first to root the Captivate glide (my first Android phone), and submitted the A2DP bitpool patch; I was active in the n900 community. I hope everyone understands that I'm doing my best here!
I hope the technique proves useful to people, and if there is in fact contention at the kernel level, I hope it's solved so we all benefit.
Version 2.0.0 attached. No changes.
Version 2.0.0b1 attached. New performance profile selector, I/O queue extender, and power saving control. Improved root checking.
Version 1.4.0 attached. Major refactoring. Service control now fully asynchronous.
Version 1.3.1 attached. No changes from 1.3.1-beta.
Version 1.3.1-beta released. New root check method during ANR-sensitive code.
Version 1.3.0 attached. Proper IntentServices for process control, and notification on upgrade / loss of root / autostart failure.
Version 1.2.9 attached. Yet another update to the upgrade/autostart code.
Version 1.2.8 attached. Asynchronous startup of rngd during boot; this should solve the remaining autostart problems some users have reported.
Version 1.2.7 released. This version introduces a much more efficient suspend-on-sleep mode for rngd.
Version 1.2.6 released. This version reverts the suspend-on-sleep rngd change which may have been contributing to new latency. I'm sorting out a better way of implementing it.
Version 1.2.5 released. This version should fix the autostart failure some users have seen.
Version 1.2.4 released. This version implements a progress bar displaying your currently available entropy, as well as automatic rngd restart on upgrade.
Version 1.2 released. This version implements rngd suspend-on-sleep, and contains minor user interface updates, more robust process and superuser checks, and a new icon (thanks Nathanel!)
Version 1.1 released. This version uses the release signature, so you will need to uninstall the old XDA version first!
Download and flash this if you dont know what to download xD Click here!
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