Here's how Pixel's ‘seamless updates’ became seamless

Google has recently rolled out the Android 14 QPR2 Beta 1 update, which brings considerably faster installation speeds to seamless updates on the last two generations of Pixel devices. Notably, it has reduced the installation time from an average of 30 minutes (sometimes it would take nearly an hour) down to nearly 10 minutes or sometimes even less than that.

Of course, there are some noteworthy optimizations under the hood, that has helped reducing the installation time. Artem Russakovskii on X has explained the Google managed to accelerate the installation process.

A closer look at seamless updates’ acceleration on Pixel devices

There are three primary improvements in the installation process that contribute to the faster speeds, one of which is the parallelization of compression operations. The installation process requires the compression of thousands of small blocks. Parallelizing this step made the whole process 26% faster, says Russakovskii.

Additionally, Android now batches operations for those small data blocks during the update process. Previously, the OS would perform separate writes for all individual blocks, but it now executes a single write combining all the blocks. This alteration led to a 24% reduction in install time, contributing to the efficiency of the update mechanism.

The compression and parallelizing process mentioned above is part of general AOSP improvement. But there’s another trick that is exclusive to the latest Pixel devices and brings most of the benefits.

It is the transition from the older GZ compression method to the LZ4 method. Described by Google as “extremely fast compression,” the LZ4 method delivers a notable 50% reduction in install time. This enhancement is exclusive to the Pixel 7 and Pixel 8 series including the Pixel Fold and Pixel tablet.

The shift to LZ4 appears to leverage multi-core CPUs, with Tensor G3’s mid-cores aiding in speeding up the process, particularly noted during the installation of Android 14 QPR2 Beta 1 on the Pixel 8 Pro.

Google’s success in optimizing OTA update installation speed is expected to guide other OEMs to implement the same.