[Nexus 7 Q&A, Help & Troubleshooting] GedBlake:
Hi, gsindl00...

Jellybean 4.3 build JWR66Y (stock rooted) is running great on my Nexus 7... no lag at all.

A question... how much free space do you have left on the internal storage of your Nexus 7?

I ask because a recent experience of mine occurred that may have some bearing on your problem.

I have a 16 Gb WiFi only 'grouper' Nexus 7... but only 13.24 Gb is available to the the user.

Now, at frequent intervals I make Nandroid backups using TWRP. These backups take up significant space, routinely clocking in at around 2.5 Gb's. Due to their size, and for this reason, I only ever keep two backups on my Nexus 7 at any one time - an 'untouched, unmodified and unrooted' backup of factory stock, should I wish to quickly (for whatever reason) restore back to pure factory (without having to pull out my laptop and resort to fastboot)... this backup clocks in at around 600 Mb. This backup never gets deleted, and remains constantly on my Nexus 7.

The second Nandroid backup is a backup of my current setup, and frequently gets deleted and made anew, roughly once a month.

Several days ago, I created a new Nandroid, BUT FORGOT TO DELETE MY OLD ONE. As I have already mentioned, these backups are quite large, and with everything else on my Nexus 7 (pics, movie clips and music), this pushed my available user space down to 1.27 Gb.

This very low available user space had a significantly deleterious effect on the performance of my Nexus 7.

After booting the device, the white-on-black Google screen would appear (as normal), after which, the pulsing luminescent 'X' boot animation would then seemingly take forever to appear, and then hesitantly:confused: (as though the device was struggling to boot).

Anyway, it did boot and upon success, my widgets (I have several), would all have to reload again, which took a good half minute or so. Normally, they just appear on the Nova launcher desktop instantly. Several reboots later, and the lag and slow boot persisted, as well as the slow loading of widgets.

This peculiar behavior went on for several days... I couldn't understand it!

I was on the verge of restoring back to stock, when I remembered the undeleted Nandroid backup.

So, booting into TWRP, I deleted the old Nandroid backup, and for good measure, I wiped Cache and Dalvik cache.

Upon reboot, I discovered I had a more healthy 4.9Gb of user space available, and the lag was gone:).

Anyway, my point is this (and it really has nothing to with Nandroids or TWRP)... make sure you have at least 4Gb of free space on your device. Delete stuff you don't need (or backup to your PC), and occasionally use a cache cleaner like

Clean Master

.

Also, if you have TWRP installed, clearing out Cache and Dalvik Cache sometimes helps.

----------------------------------

Since Jellybean 4.3, fstrim/discard has been fully implemented (it was always there in 4.2.2, but it wasn't enabled). Under 4.3, fstrim/discard now runs regularly, but only under certain conditions...

QUOTE- "The folks at AnandTech mention how TRIM will run when your tablet is idle with the screen off and sitting with a battery life of 70 percent or greater. The issue with the previous model Nexus 7 is that while TRIM support has been around since Android 4.2 — it wasn’t enabled. And regardless of how good a feature can be, if it is turned off then it will not do anything."

SOURCE -

http://androidcommunity.com/nexus-7-2012-getting-performance-boost-with-android-4-3-update-20130729

.

See also

here

for more technical and interesting info on 'fstrim'.

So, 'fstrim' is now part of Jellybean 4.3... and will run at regular intervals, providing the battery is above 70% and the Nexus 7 is 'sleeping'. But there's nothing to stop you from running 'fstrim' yourself with

this app

. Particularly after you've JUST deleted some really big files. You will need to be rooted of course.

Right... apologies for the length of this post... just wanted to reference my own experiences in the hope it might help.

Rgrds,

Ged.