Hey everyone,
On some (older) versions of Android, the JVM (and other components) read large amounts of random data from the blocking /dev/random device. On newer builds, this problem has been solved, yet depletion of the input entropy pool still seems to slow devices.
So, I cross-compiled rngd, and used it to feed /dev/urandom into /dev/random at 1 second intervals.
Result? Significant lag reduction!
Chrome, maps, and other heavy applications switch instantaneously, and map tiles populate as fast as I can scroll. 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!
Version 1.1 attached. This version uses the release signature, so you will need to uninstall the old XDA version first!
This version fixes the issue some users were seeing on later Jellybean ROMs, where the UI would misreport the RNG service status.
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.
Caveats
There is a (theoretical) security risk, in that seeding /dev/random with /dev/urandom decreases the quality of the random data. In practice, the odds of this being cryptographically exploited are far lower than the odds of someone attacking the OS itself (a much simpler challenge).
This may adversely affect battery life, since it wakes every second. It does not hold a wakelock, so it shouldn't have a big impact, but let me know if you think it's causing problems. I can add a blocking read to the code so that it only executes while the screen is on. On the other hand, many of us attribute lag to lacking CPU power. Since this hack eliminates almost all lag, there is less of a need to overclock, potentially reducing battery consumption.
There has been a large amount of speculation on why/if this actually improves performance on ICS+ devices. I'm continuing to investigate and will post updates to this thread.
If you try it, let me know how it goes.
ROM builders - feel free to integrate this into your ROMs (either the .apk / application, or just the rngd binary called from init.d)!
If anyone's interested, I've launched a paid app on the Play store for non-xda users. As I add features I'll post the new versions here as a thanks to you guys (and xda community at large for being such a great resource). But if anyone's interested in the market's auto-update feature, just thought I'd mention it.
Cheers!