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While I was writing an answer to this question, my browser tab crashed. That's a browser bug, obviously, not a Stack Exchange bug, but it's also partly two Stack Exchange bugs:

  1. The preview code is obviously being too demanding on the browser.
  2. Stack Exchange saved a draft of the answer, but that draft was missing about 90% of what I'd written, which is pretty useless.

My browser is Chrome 85.0.4183.121 on Linux/x86_64. I blame the crash on the preview code because I noticed that as I was typing, the preview updates took longer and longer (maybe about ½ second just before the crash). Previews have been consistently taking longer than they used to (it's a noticeable amount of CPU time, even without MathJax or code formatting) for the past few months; I'm pretty sure this started with the switch to CommonMark, because I noticed it happening without a browser upgrade (or even restart) and as far as I recall now this is the Stack Exchange change that had just happened. My answer was moderately MathJax-heavy, with about 20 simple MathJax fragments: I've written answers that were a lot heavier in the past, but none since the markdown engine switch.

Eventually, at one point, a preview update locked the tab up for several seconds of CPU activity, then the tab crashed with an “Aw, Snap!” message indicating a SIGTRAP. I didn't have time to check the memory usage before the tab crashed, but it can't have been that bad, because my system (which has swap) wasn't thrashing.

Unfortunately, I don't have a copy of what I had typed. I may or may not post something vaguely like it later if I have the courage to write it again.

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  • $\begingroup$ I haven't noticed any performance issues after the CommonMark migration, but I have lost large parts of answers before, where it turned out only a small part of the draft was saved. I guess we may be able to blame caching on that one, judging from how the system is (was?) implemented. Still, pretty annoying. I tend to save a local copy of drafts nowadays when I start to suspect things are breaking. $\endgroup$ – Discrete lizard Oct 12 '20 at 18:06
  • $\begingroup$ Is this still happening? We've tried a few repros, but everything seems to be working fine. (To be fair, not 100% sure if those attempts were on Linux. I'm going by internal ticket notes here.) If you're still seeing perf issues, though, can you include a sample of the input that causes them, please? $\endgroup$ – Adam Lear Feb 20 at 0:29
  • $\begingroup$ I couldn't reproduce it. But I don't know what I'd typed… My original answer was more MathJax-heavy than what I finally posted. I'm not so much concerned about the crash, really (after all, it's the browser's fault) than about the unreliability of drafts. I find that when I accidentally move away from an answer I'm typing (browser crash, following a link, closing a tab) and come back, SE has invariably saved a draft (assuming I wasn't composing more than one answer on the same site), but it's usually lagging behind. $\endgroup$ – Gilles 'SO- stop being evil' Feb 20 at 13:41

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