The Pixel uses a RAM cache

[tipoo]

http://arstechnica.com/gadgets/2016...ew-bland-pricey-but-still-best-android-phone/



" We reached out to the developers of Androbench about this and were told that some shenanigans seem to be happening where the "Direct I/O" calls on the Pixel are actually not that direct. Calls to storage end up going to a RAM cache instead, so you end up with ridiculously high scores of 1GB/s in some cases. Hopefully the storage benchmark developers will be able to get to the bottom of this situation, and we'll update our results when they do."



Despite breaking benchmarks, that sounds like it would add a lot to immediacy of app launches and resumes. Curious to see something like a phonebuff comparison on it, especially with the reigning champ of the iPhone 7 on that speed test.

Now, any OS, or at least consumer facing OS worth its salt should be using idle RAM to keep likely files and applications in it as long as it can. However that cached memory is flagged as purgeable should anything ever need it.

In the Pixels case, it looks like some of the 4GB is a persistent RAM cache which will always be accessed first on a directIO call.

I’d love for this to be investigated more (cough Anandtech cough)

 

[Red Storm]

I’d love for this to be investigated more (cough Anandtech cough)

Maybe when Anand was here, but I don't expect it anymore unfortunately.

 

[lothar]

Likely a thing with Nougat or the benchmarking app. Some Nexus 6P and Nexus 5X have that same issue I hear.
Here's the exact response from the developers:

Thanks for bringing up this issue to us. Appreantly, something was wrong in Pixel. Getting the sequential read performance of 2.9GB/s is only possible when the data is read from DRAM. During the microbenchmark test, we use DIRECT_IO to bypass the page cache.Hence, we suspect that DIRECT_IO might not work properly in the Pixel device.

By the way, we have found that this problem happens not only in Pixel, but also in other devices. We have scrutinized all the results of Android 7 and 7.1 devices collected in our server. We find that about 3.5% of the results showed the sequential read performance greater than 1GB/s. Interestingly, all of them were the smartphones manufactured by Google such as Nexus 6P, Nexus 5X, and Pixel. Even in the same Nexus 6P model which uses the same kernel, most of them were OK, but several devices were reporting weird read performance.