Battery Life - A Stark Contrast

We extensively covered the performance of the Snapdragon and Exynos Galaxy S9’s – what remains to be seen is how that performance affects battery life in our standard tests. Performance between the regular and larger Galaxy S9 doesn’t change, however battery life may differ based on the variant as the regular S9 sports a 3000mAh (11.55Wh) battery versus the 16% higher 3500mAh (13.47Wh) of the Galaxy S9+. Naturally the 14.2% bigger screen area of the S9+ offsets some of that advantage.

Unfortunately for this review we couldn’t get identical variants of the different SoC Galaxy S9s – our S9+ is a Snapdragon 845 unit while our S9 is an Exynos 9810 unit, so we weren’t able to execute a true apples-to-apples comparisons between the SoC variant, however as we’ll see the delta between the units is large enough that it won’t change the conclusion.

Our web browsing test tries to mimic real-world usage patterns of browsing websites. This includes iterating through a list of websites and scrolling through them. In this test, screen efficiency and battery size play a role, but also we balanced it so that it also sufficiently stresses the SoC (CPU, GPU and display pipeline) as well.

Web Browsing Battery Life 2016 (WiFi)

The Snapdragon 845 Galaxy S9+ posted excellent battery life in our test and lands only third to the iPhone 8 Plus and the Mate 9. Unfortunately we never tested the S8+ to see the generational difference, but it shouldn’t be too different from the S835 regular S8 at around the 10 hour mark.

The Exynos 9810 Galaxy S9 absolutely fell flat on its face in this test and posted the worst results among our tracking of the latest generation devices, lasting 3 hours less than the Exynos 8895 Galaxy S8. This was such a terrible run that I redid the test and still resulted in the same runtime.

I investigated the matter further to try to see if this was caused by the high energy usage of the M3 cores – and it seems it is. Enabling the “CPU limiter” (S9 PS result in the graphs) which is found in the battery optimisation options of Samsung’s firmware greatly throttles the M3 cores down to 1469 MHz, memory controller to half speed and also seemingly changes some scheduler settings to make them more conservative. This results in peak performance equal to the Exynos 8895- however the scheduler alterations also noticeably slow down UI responsiveness so it’s actually a worse experience. Nevertheless, backing off on performance results in regaining almost 3 hours.

This is such a terrible battery performance of the Exynos 9810 variant that it again puts even more clout into the new SoC. My theory as to why this happens is that not only do the higher frequency state require more energy per work done than competing SoCs – because this is a big CPU complex there’s also lots of leakage at play. The DVFS system being so slow might actually be bad for energy here as we might be seeing the opposite of race-to-sleep, walk-to-waste. The fact that Apple’s SoCs don’t have any issues with battery life in this test showcases that it’s not an inherent problem of having a high-power micro-architecture, but rather something specific to the Exynos 9810.

PCMark Work 2.0 - Battery Life

In PCMark the disadvantage of the Exynos 9810 S9 isn’t as pronounced as in the web test, however it’s again a regression to the Exynos 8895 S8 – all while not posting a meaningful performance advantage over its predecessor that might explain the lower battery life.

The Snapdragon 845 Galaxy S9+ fared relatively well, even though it’s not quite as good as other devices.

In my personal every-day usage I can’t saw that I noticed a massive disadvantage in battery life on the Galaxy S9, however my everyday usage is relatively light and I haven’t had enough time with the phone yet as a daily driver to make a final judgment. I did notice that the Exynos 9810 does shows signs of suffering in heavy tasks. Instances of Gmail syncing my inbox with a new account did once result in a warm phone while the Snapdragon 845 Galaxy S9 did not showcase this characteristic.

I can’t fault the Snapdragon S9+ in the time I had it, but again I haven’t had enough real time with it to really judge it subjectively. As far as AnandTech testing goes, the data speaks for itself and based on what I’ve seen I strongly do not recommend the Exynos variant of the Galaxy S9 in its current state, especially if you’re a regular user of heavy apps.

Over the coming weeks I’m planning to try to dive into the workings of the Exynos 9810 and post a follow-up article on whether it’s possible to improve both in terms of performance as well as battery life if one changes the way the SoC’s scheduler and DVFS works. In the eventuality that Samsung updates its firmware to resolve these large issues with the Exynos Galaxies, then we’ll revisit the matter as soon as possible.

Display Evaluation & Power Camera Architecture & Video Performance
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  • Andrei Frumusanu - Monday, March 26, 2018 - link

    I literally uploaded a 4K60 video on the S845 S9+. They always had it.

    https://youtu.be/9g88TIi-p2U
    Reply
  • N Zaljov - Monday, March 26, 2018 - link

    This article, as always, is some top-quality stuff. Really enjoyed reading it, Andrei!

    As for the CPU: Ah! Hotplugging! We finally meet again after all these years! How's it going ever since you've been banned from this planet? ;-)

    Honestsly: I don't think that a company like S.LSI would seriously start fiddling around with deprecated mechanics like hot-plugging and slow asf DVFS scheduler settings, if there wouldn't be a major architectural/implementational flaw within the M3 cores.

    This might sound like a far-flung theory, but could it be possible that there might be something wrong with the way how the M3 cores handle power-gating in a way that it just takes the CPU way too long to "warm up" cold blocks (like Register files, INT- & FP-Units etc.) that aren't utilized, which kind of translates into these terrible response times? While this might only explain the poor DVFS implementation, I don’t really find a reason why „hot-plugging“ should be the way to go for any sane semiconductor engineer or BSP developer.

    Yes: It’s easier to implement and it costs less transistors (and wiring as well), but with modern process nodes, the added transistor budget simply wouldn’t even matter when you compare it with the huge amount of logic that’s there. In fact, I wouldn’t be too surprised if the hardware actually supports a more fine-grained control (with stuff like WFI for instance...), but at some point the BSP developers simply said „well, this stuff has already been working for us in the 5410 and 5420, so let’s go!“. Duh.

    On the GPU side of things though, it doesn't look as bad as I initially suspected: S.LSI greatly increased their effort into improving perf/w of their Bifrost implementation, a big differentiationpoint between HiSilicon's last two generations and the appalling heap of junk of a GPU implementation in form of E8995's G71MP20.
    Reply
  • Andrei Frumusanu - Monday, March 26, 2018 - link

    > if the hardware actually supports a more fine-grained control (with stuff like WFI for instance...)

    WFI, core power down and cluster power down all work perfectly as intended and are being used. If they wouldn't be then this thing would melt. They use the hot-plugging just to force the scheduler. There's also no way to know which parts are of the S.LSI BSP and which parts are from the mobile division. I'm very sure all of this is likely mobile division additions however it can't be confirmed as they both use the same copyright name (Samsung Electronics) in the source files.
    Reply
  • N Zaljov - Monday, March 26, 2018 - link

    Thanks for clarifying. My apologies, I skipped the part that mentions "...to force thread migrations between the cores...".

    Another question: What software build is your S9 running on? The last update (afaik Build RC5) supposedly fixed some performance related issues and I was wondering, if they changed the bias of their governor (or at least tried it).
    Reply
  • Andrei Frumusanu - Monday, March 26, 2018 - link

    The review was done on ARC5. Reply
  • Quantumz0d - Wednesday, March 28, 2018 - link

    Thanks for this Andrei, Also this article is pure gold !!

    Loved every bit of it from the Architecture to the benches, explanation, the wording, fantastic work there sir.

    That Googles ridiculous decision to block Accessibility & the most essential 3.5mm jack mention and honest true facts about it in simplistic way yet hitting the bullseye, and the flow of the article is just marvellous art. Keep it up !!

    One more thing I would suggest is, you might consider teaming up with Supercurio from XDA who built the Voodoo sound for Wolfson chips for Audio Analysis would be a great addition !!

    Thank you again ! Looking forward for more.
    Reply
  • tuxRoller - Monday, March 26, 2018 - link

    The kernel has recently (https://lwn.net/Articles/737157/) completed a, nearly complete, rewrite of the hot-plugging core. This has made it both much faster and more reliable. So, it's very far from deprecated (though I won't speak to the way Samsung is using it here). Reply
  • Quantumz0d - Wednesday, March 28, 2018 - link

    Exactly what I thought. After the SD810 the Hotplugging is very bad and inefficient. I wasn't surprised when the initial fantastic analysis was done by Andrei, but its really bad about the Battery life regression. Also I don't get this hype around the A series chips after that massive battery fiasco, they tune them so badly and look at the iPhone internals they barely have metal plate contact for heat transfer. Yeah I agree on the GPU part too surprised to see this. But I think Samsung wanted to have similar performance between the devices and down tuned the CPU in one and GPU in another...pure speculation.

    Apple manages to cheat always and damn all these idiotic sites who only show GB and say here's the Exynos and all. I didn't like how Samsung advertised the new SoC chip likes of Apple going for peak and not sustained.

    I think that SD85x might have full custom cores like the OG Kryo from 820, I wish that to happen. Feels great to see how Adreno crushes the A11.
    Reply
  • zer0hour - Monday, March 26, 2018 - link

    Superb article, certainly of quality that lives up to the Anandtech name. I've been waiting for details of the E9810 S9 for ages, and this article is really the only one that explores the reasons for its weird real world vs synthetic performance. Reply
  • Speedfriend - Monday, March 26, 2018 - link

    After seeing the S9 initial performance impressions and being in the UK, I decided to go for a pixel 2 XL for myself and an S8 to replace my gfs iPhone 6S. Very happy with both decisions, the pixel 2 XL is so fast and the S8 was a crazy deal.

    It is a real pity that performance and battery life are so hampered in the s9810 versions as I have loved my last few Samsungs. But if Google makes another good pixel this year, I can't see myself going back.
    Reply

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