[CB-13559] Poor performance and crashes marshalling large ArrayBuffers from JS to Native side on iOS

• Type: Bug
• Status: Open
• Priority: Critical
• Resolution: Unresolved
• Affects Version/s: cordova-ios@4.4.0, cordova-ios@4.3.0, cordova-ios 4.5.0
• Component/s: cordova-ios

Environment

iOS 10.3 Simulator
Using cordova-plugin-wkwebview-engine

• Assignee: Unassigned
• Reporter: Tim Hambourger
• Created: 09/Nov/17 22:35
• Updated: 27/Jun/18 23:26

Description

I'm doing performance analysis on an application that's attempting to write an approx. 10 MB Blob to disk using the File plugin. The uint8ToBase64 function called by iOSExec looks like a particular bottleneck. I'm seeing large memory increases followed by GCs taking approx 1.5 secs. The attached screenshot has a typical Safari timeline.

After some initial testing, it looks like re-implementing uint8ToBase64 using String.fromCharCode and window.btoa, rather than string appending, might yield some improvements. Some alternate implementations at https://github.com/github-tools/github/issues/137 and https://stackoverflow.com/questions/9267899/arraybuffer-to-base64-encoded-string.

Is this something you would consider taking a look at? We're also weighing strategies to reduce our file size and the frequency of our writes, but a platform-level fix would be a huge help.