Fix crash when importing big linux perf tool files

[Goose97]

Currently, importing files generated by linux perf tool whose some blocks exceed V8 strings limit can crash the application. This issue is similar to the one in #385.

This PR fixes it by changing parseEvents to work directly with lines instead of chunking lines into blocks first.

Fixes #433

[coveralls]

coverage: 42.952% (-0.06%) from 43.012% when pulling e1dacfe on Goose97:fix-large-file-crash into 26884c1 on jlfwong:main.

[jlfwong]

Nice! A few things inline that need changing, then assume CI passes this should be good to go.

Also, just as a sanity check, this does now load the massive file you referenced in the issue, right?

[jlfwong]

I'm also curious how quickly such a large file loads, and what the performance bottlenecks of the load are

[Goose97]

Also, just as a sanity check, this does now load the massive file you referenced in the issue, right?

Yes, it works ok now

[jlfwong]

Thank you!

[Goose97]

I'm also curious how quickly such a large file loads, and what the performance bottlenecks of the load are

Ironically, I just realize that it's not a linux perf tool file but a Brendan Gregg-format file. Oh silly me. The code just accidentally hits the error part and crashes.

Anw, it took ~23 seconds to import the file and took about ~1 second to render. Out of 23 seconds, ~2 seconds was reading the file into the buffer. The rest is parsing. I have the Chrome profiler dump but it's too large to attach to Github. Do you want to have a look?

System info:

• Chrome version: 114.0.5735.133
• OS: macOS Monterey 12.6.5
• Memory: 16GB

[jlfwong]

Ironically, I just realize that it's not a linux perf tool file but a Brendan Gregg-format file. Oh silly me. The code just accidentally hits the error part and crashes.

Ah jeez, I see -- for plaintext files with no known file extension, we always try importFromLinuxPerf before importFromBGFlameGraph.

If you can think of a way of avoiding that by doing some cheap heuristic detection on one format or the other, I'd take a PR to do that too.

To see if that's worthwhile for performance reasons, you could delete the lines that run importFromLinuxPerf, and try to import the massive file you're working with.