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Nexus 6 Performance With Android 5.1

Storage Performance

The specific issue vexing the latest Nexus is that the hardware encryption engine provided by its Snapdragon 805 SoC is disabled, forcing all file system encryption/decryption to be executed in software on the CPU.

In November and early December of last year, during the development of the 5.1 update, there was a series of software commits enabling and disabling the hardware based encryption engine. Ultimately, hardware encryption was disabled again for the Nexus 6 5.1 update. We asked Google about this decision, but they would not provide an answer.

Even though file encryption is still funneled through the CPU, the update should still improve storage performance. The encryption engine can now utilize NEON instructions and has additional threads at its disposal. Previously, with only two CPU cores online, the encryption driver was allocated only two threads to handle file read and write requests. The 5.1 update however, keeps all four cores active all the time, which means the encryption driver now has up to four threads to perform its work.

AndEBench Pro Storage Test

512BSW512BRW4KBSR4KBSW4KBRR4KBRW16KBRR256KBSR256KBRR
Galaxy Note 4 (5.0.1)449102520877334020425799256653125891127268
Nexus 6 (5.0)2097239084132274495951129692310724857
Nexus 6 (5.1)169636871498261165676150603093232646
Nexus 6% Diff-18.9%-12.0%-4.1%-25.7%-17.9%-4.6%16.1%33.9%31.3%
First letter: S=sequential, R=randomSecond letter: R=read, W=writeValues in KB/s - Higher is betterFile Size: 5, #Folders: 3, #Files/Folder: 1

The results from the AndEBench Pro storage test show nice gains reading larger blocks of data, just over 30%. Unfortunately, reading and writing smaller blocks of data generally show a performance regression. Increasing the file size parameter does improve the numbers, causing a few negatives to flip positive, but the overall trend remains. Based on these results, it appears that disabling Qualcomm’s thread migration boost feature has a greater impact on file encryption performance than adding more threads or using NEON instructions.

What this test fails to capture, however, is the storage performance in real-world scenarios. Reading and writing to storage does not happen in isolation. Instead, the encryption driver must fight threads from the active program, background tasks, operating system, user interface, etc. for CPU time. Having all four cores active all the time means more resources are available to the system and eliminates the latency involved in bringing the other cores online. In theory at least, storage performance in these noisy scenarios should at least be more consistent with the 5.1 update.

Even with the uplift in some scenarios, the Nexus 6 running Android 5.1 still trails the Galaxy Note 4 by a significant margin. If FDE is going to be a viable option, which it needs to be, then Google needs to resolve the issues surrounding full hardware encryption.

  • ZolaIII
    Just to point out how CPU clocking logic effect busses on Qualcomm SoCs. For instance if 1 core CPU frequency fell down under the minimum frequently than is tied to max bus frequency it will narrow & memory bandwidth & this will impact GPU performance badly under GPU intensive tasks. For me it looks like that on-demand scheduler is working more as it should under 5.1. Including patch sets from Linux kernel 3.12~3.21 (on demand to use more mid frequencies) should be just enough to address performance regressions still savings (even litle more) juice. They should really disable file encryption on any ARM V7 build. Switching to last stable GCC should increase user experience greatly, it's funny they still use 4.6. To address possible fluctuations & determine real impact of changes do the tests again with performance governor & disable MP decision (hot plug) for GPU tests.
    Reply
  • zodiacfml
    Ouch. Glad I bought the N5 last year.
    Reply
  • endeavour37a
    I have an old LG G2 and it does not even have filters :(
    Reply
  • theusual
    Be sure to upgrade 'Android System WebView' through Google Play as well as for me it didn't upgrade automatically and was causing app issues.
    Reply
  • Plyro109
    Sorry. Browser seems to be autofilling and submitting in every comment thread I visit.
    Reply
  • Tracy Kohler
    Get that stupid bar off the top of my screen please! It takes up a whole INCH of screen space (and vertical space is LIMITED already on this wide CRAP they call monitors today).

    I guess I'll have to come up with a way to kill it and still be able to navigate, other than scrolling. Go back to pages with a bar at top or bottom for index. While your at it FIRE the guy/gal who decided an inch of real estate on a monitor is OK to block all day. He/she will only piss off users over and over (hired from win8 team?...LOL).
    Reply
  • Senecaz
    TL, DR : Lollipop s*cks! next update please...
    Reply
  • musical marv
    15881932 said:
    TL, DR : Lollipop s*cks! next update please...
    Why do you say Loliipop sucks?

    Reply
  • musical marv
    15881932 said:
    TL, DR : Lollipop s*cks! next update please...
    Back Up what you post here and do not ignore it.

    Reply
  • endeavour37a
    I thought Tom's was a place we could have opinions and points of view we could share and express freely, how does one back up what they like and don't like? I sort of like 5.0 but it's just fine if some else does not, I ignore a lot of stuff myself.
    Reply