I've been poking and prodding at my RAGE demo as onGameStart draws nearer, trying to clean up the code and squeeze a bit more performance out of it. During this testing I've made a depressing observation:
Chrome's performance, in reference to speed of texture upload, sucks. And by "sucks", I mean as it atrociously, painfully, unforgivingly slow.
The most technically demanding aspect of the RAGE demo is the constant texture swapping that happens every few steps. We pre-allocate an array of 30-40 some 1024x1024 textures (exact number depends on the map) and as we progress along the path we identify upcoming textures that will be needed, download them, and push them into an unused texture, hopefully well before that texture is actually needed. The Webkit and Firefox nightlies can handle this fine (though we do drop a frame or two here or there) but Chrome 14 on my Mac basically breaks down and cries when asked to do this. You can see for yourself in my simple jsperf benchmark.
So, to put this in perspective: Chrome is able to squeak out a measly 22 texture uploads per second at 1024x1024. That's ~50ms per upload that your browser is blocked on that call. If you are shooting for a 60hz game (~16ms per frame) this means that uploading one texture to graphics memory just caused you to drop 3-4 frames. One texture, 3-4 frames lost. Ouch! For a medium that will be highly dependent on streaming, that hurts!
By comparison, Safari 5 gives me 62 uploads per second (ie: you may drop a frame here and there, but performance will stay pretty solid.) and Firefox 7 blasts out a whopping 188 uploads per second! That's ~8ms per upload, leaving lots of breathing room for rendering!
It's a real shame too, because in most other ways Chrome seems to be the most solid performer with WebGL. If I chop all the textures in my RAGE demo down to 512x512 I can run at a rock solid 60hz with no tearing or stuttering. (Though the texture upload is still painfully slow compared to the other browsers.)
Maybe the benchmarks look a lot better on Windows, but I don't have a machine to test that with right now. Regardless, this is something that the Chrome team really needs to smooth out. Pretty please?
(All timing is taken from my iMac)
[UPDATE: I wrote up a bug report on the issue, lets see if it goes anywhere. Similar reports have been added in the past, as seen in the comments on this post]
