Hey everyone! For the past several patches some of you have been reporting some in-game performance issues, and we're working to address them. We want to take a moment to review the situation and explain our approach.
There are actually several problems we've been dealing with, and we'll cover each individually:
Average FPS decreases
Increase in FPS hitching and frame drops
Complete game freezes
#Average FPS decreases
Average FPS is just that—the overall average number of frames rendered on your screen per second across an entire game. While important, this measurement isn't actually the most critical since as long as your FPS is stable, you're getting information at a consistent (though perhaps suboptimal) rate.
Another important note when discussing FPS: the number you see in game might be higher than what your monitor actually provides. Most monitors are 144Hz or 60Hz, which indicates the highest number of frames that monitor can render per second. If you, for example, are getting 170 FPS on a 144Hz monitor, 26 of those frames don't actually exist.
_PBE: Average FPS by system specs. Higher is better._
Average FPS significantly improved in 8.13, but most of that improvement has been slowly lost in the patches following. This happens because there's no single "FPS tool" to maintain—every time we add or adjust something in-game, it can impact performance. These days, new and updated content (skins, champs) tends to include various features (visuals, ability functionality, etc) with higher performance demands than older content. Making cooler stuff stretches the limits of what the game can do before FPS begins dropping. We've been working on a feature to meaningfully improve FPS, but have run into some challenges—more on that in a bit.
_Frame rates as of Sept 18._
#Increase in FPS Hitching and frame drops
FPS hitches are short, sudden drops in FPS, with frame drops being the worst cases (FPS dropping down to zero). Hitches are more impactful than low average FPS because, for a moment, the game gives you far less information than you're used to, throwing off your decision-making. Hitches are also generally triggered by something happening in the game, like casting an ability—the times where you most need the game to be telling you what's happening.
_PBE: Hitches per game system. Lower is better._
Per the graph above, FPS hitching started getting worse in 8.15. We encountered significant issues while testing 8.16, but were able to address the worst of them before shipping. New issues then emerged in the second half of 8.17 which we couldn't fully resolve before shipping. Fortunately, we made significant progress in 8.18, with only two systems (one gameplay event handling; the other rendering-related) still elevated above pre-8.15 levels.
#Complete game freezes
Complete game freezes occur when your game locks up completely, and the only solution is to ALT+F4 and restart the client. This is by far the worst of the issues we're discussing today, but fortunately the one that's been contained. During patch 8.16, we tested a feature meant to dramatically improve FPS for systems with multi-core processors (the one we alluded to earlier). While we saw the FPS gains we were looking for, they unfortunately came with a massive increase in the frequency of game freezes, so we disabled the feature. It was accidentally re-enabled when patch 8.17 shipped, causing another increase in game freezes until we turned it back off again. As of now, game freezes are back under control.
#Our Next Steps
We’re continuing testing to try to isolate why some systems were freezing with the multi-core FPS fix. Once that’s ready, we’ll be able to ship a boost to FPS for many players. Otherwise, we’re monitoring FPS and hitching levels in order to ensure that performance issues don’t return. We’re also working toward improving our ability, internally, to attribute performance degradations properly to the game feature they are coming from (VFX, champions, items, etc.) so that we can fix issues faster going forward.