Improving The Exynos 9810 Galaxy S9: Part 2 - Catching Up With The Snapdragon
by Andrei Frumusanu on April 20, 2018 9:00 AM EST- Posted in
- Mobile
- Samsung
- Smartphones
- Exynos 9810
- Exynos M3
- Galaxy S9
Conclusion
With these pieces I wanted to see what’s possible with the Exynos 9810. There’s definitely still room for improvement; I’m still sure a properly tuned WALT configuration like on the Snapdragon 845 S9 or the Pixel 2 would further improve the performance or battery life of the Exynos S9. I didn’t want to go down that rabbit hole for a custom kernel, for now the improved PELT changes are just as good as it reasonably gets.
One thing I did discover is the performance discrepancy between the M3 and Kryo 385 when it comes to synthetic benchmarks versus some of the web benchmarks. While 1794 MHz is enough to match the A75-based CPU cores of the Snapdragon in GeekBench or SPEC, I wasn’t able to match the higher performance in the web benchmarks unless I raised the clocks to around 2.3GHZ. I can now dismiss software as being the main culprit here, and instead there’s more fingers pointing at the micro-architecture of the M3. This has some relatively big repercussions as it begs the question of what kind of workload is actually more representative of overall Android smartphone use-cases.
The above graphic is my best guess on what the performance/power curves look like. These are based on scheduler cost tables, voltage curves and correlations to actual measured power on certain points. The big question here is what is the actual representative positioning between the two architectures in terms of performance? As we saw in part 1, the M3 can win on average in workloads such as SPEC at the same performance points as the S845. However to reach the higher performance of the 845 in web workloads we need to raise the clocks, and this of course would shift the efficiency curves around with a much bigger favour towards the Arm cores. The average is probably somewhere in-between, and Arm and Samsung hopefully have a more complete view in terms of workload characterization.
What is indisputable is that the M3 lags behind in the lower frequency states. Here, Samsung’s cores just stop scaling further down in voltage after 1170MHz, while the Snapdragon and Arm cores' power curves are just a lot steeper. Again the absolute difference is arguable depending on workloads, be it 25% or 100%. Unfortunately at this point we’re talking about insurmountable physics and there’s just no software optimisation which will overcome this.
In the end the Exynos S9 was hampered on two fronts: one being just a very unoptimised BSP (Board support package; kernel, drivers, etc) by S.LSI (With the Mobile Division also possibly being a factor), particularly the seemingly senseless chasing of higher synthetic benchmarks scores such as GeekBench. which in turn backfired very badly in any real-world workloads. Qualcomm provided Samsung with an excellent baseline BSP on the S845 S9’s – so for S.LSI not being able to do the same is just unfortunate. The other front where the Exynos S9 was hampered was that the M3 just seems oversized and power hungry, and it can’t sufficiently act as the efficient workhorse for general workloads. Compounding problems, this comes at a cost of battery life. Here there’s just a lot more to be done to fix the efficiency and the performance discrepancy relative to Arm’s cores.
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N Zaljov - Sunday, April 22, 2018 - link
For this part, Spock should‘ve used a tunnel bore instead of a mere chainsaw, because a chainsaw doesn‘t seem to accomodate the right amount of „POWER!“ that one would require in order to deal with Samsung‘s crapload of shady implementation. SCNRdjayjp - Friday, April 20, 2018 - link
Wow, amazing work. The definition of above and beyond. I would submit this data to Samsung.StormyParis - Friday, April 20, 2018 - link
Fascinating. Thank you !mad_one - Friday, April 20, 2018 - link
Lovely article!Software can still play a part in the web workloads, as the Javascript and browser engines are probably better tuned for the ARM cores. Of course tt could also be the M3 core struggling to extract enough ILP out of the branchy and cache unfriendly JS code, ARM has certainly tuned their cores for this over the years.
repoman27 - Friday, April 20, 2018 - link
Outstanding work, and much appreciated. Thank you, Andrei!I fully recognize that one only has so much time to commit to writing pieces like this, and that it requires a fair amount of personal interest in the subject matter at hand to do it right. However, it would be great to see Anandtech do a deep dive into the iPhone battery issue. Obviously Apple is intentionally opaque regarding a fair amount of the iPhone and iOS internals, which would make it somewhat more challenging. But I have yet to see anyone publish anything that even quantifies the basics of the reduced performance modes introduced by the various software updates. I can't imagine it would be too hard to figure out what the maximum clocks are with a new battery vs. what appear to be four distinct lower performance modes, or to determine what metrics are used to trigger those modes. Maybe the folks at the kiosk that does aftermarket battery replacements at the local mall would be willing to set aside a box of pulled batteries for testing? Such an article would arrive late as far as the media cycle is concerned, but this is an issue that continues to affect hundreds of millions of people worldwide.
A few years back, Brian Klug used to catch a lot of flack for being biased, before he (and Anand) left to join Apple. And maybe you'll end up at Samsung in the future, like Kristian. But while I think your tone was quite even handed and appropriate in this article, you seemed much more inclined to denounce Apple as deserving of a class-action lawsuit before doing any in-depth testing in regards to their recent power / performance issues. In your opinion, what is the appropriate response from Samsung in this situation? I mean, obviously pushing out a software update that improves performance would be a good start, but should owners of Exynos 9810 variants of the Galaxy S9 sue for damages and extract their pound of flesh?
BurntMyBacon - Monday, April 23, 2018 - link
@repoman27: "But while I think your tone was quite even handed and appropriate in this article, you seemed much more inclined to denounce Apple as deserving of a class-action lawsuit before doing any in-depth testing in regards to their recent power / performance issues."I think the difference in tone reflects the difference in situation. In Samsung's situation, the product came to market with a set level of performance and battery life. Very early in the lifecycle of the product, It was discovered that better software would improve their situation to a more or less extent on one or both fronts. In Apple's situation, the product came to market with a set level of performance and battery life. After a certain time period and as a direct result of a software update, performance suddenly and inexplicably (until it was investigated) dropped for older phones (more cycles on the battery).
Samsung's situation left their solution looking immature at best and their engineers looking incompetent at worst. In either case, their misstep appears to be unintentional and only serves to hurt sales of a new product. Apple's situation left them looking misguided at best and abusive(?) at worst. In either case, their actions appear to be intentional (well meaning or not). The actions only affect phones later in their life cycle and, whether as an unintentional side effect of their actions or as the primary goal of their actions, Apple stands to gain by virtue of prompting upgrades. Some people tend to believe the upgrades were the primary goal due to Apple's locked in ecosystem design and marketing strategy, but it could just as easily have been an (un)fortunate side effect of them trying to mitigate another potentially serious blemish to their user experience. Perhaps a case of the cure being worse than the disease. Like you, I wouldn't mind a more in depth look at the situation that could help clarify this.
In any case, I think the difference in tone comes down to the clear lack of intention on Samsung's part (they don't benefit from this) and potentially well meaning but certainly intentional actions on Apple's part.
B3an - Friday, April 20, 2018 - link
Excellent article Andrei. One of the best on here in a long time.Glad i got a import Snapdragon S9+, because it seems no software update will ever properly fix the poor battery life and *actual daily usage* performance of the Exynos version. Absolutely pathetic how poorly Samsung handled all this though. So many poor decisions. Honestly the people responsible need to be fired. People shouldn't have to go out of their way to buy imports.
serendip - Friday, April 20, 2018 - link
This article will probably be used as a chainsaw by Samsung top management to get rid of everyone who screwed up the Exynos S9. It's sad how seemingly chasing synthetic benchmarks led to bad decisions from chip design onwards.madurko - Saturday, April 21, 2018 - link
AFAIK they are comparing the smaller S9 Exynos (which has 3000mAh battery) vs. S9+ S845 US version (3500mAh). So the battery life obviously will be better with the bigger bro. But, anyway, this doesn't make the exynos version any better.mczak - Friday, April 20, 2018 - link
Very interesting article indeed.I agree the M3 core looks a bit oversized for a smartphone - but a tweaked version of it on 7nm might fare a lot better. For this generation, it definitely wasn't worth the effort over standard A75.
And, by the looks of it, recognizing the power issues, samsung made things worse with an inadequate scheduler.
I wonder if actually the SD845 could get better battery life at very little performance cost by disabling the highest frequency state - that sure looks inefficient as hell. (Albeit that could only widen the battery life gap between the two S9 versions...).
The discrepancy between web tests and microbenchmarks (and spec) in efficiency is also quite interesting - while I'd agree it might be more difficult to extract good IPC of these web tests (putting wide cores at a disadvantage) apple seems to have successfully done so, though I'm ignoring if through software or hardware means.