Bug 235448

Summary: file.stream() is slow and CPU-bound
Product: WebKit Reporter: Jacob Bandes-Storch <jacob>
Component: New BugsAssignee: youenn fablet <youennf>
Status: RESOLVED FIXED    
Severity: Normal CC: achristensen, ap, cdumez, webkit-bug-importer, youennf
Priority: P2 Keywords: InRadar
Version: Safari 15   
Hardware: Mac (Apple Silicon)   
OS: macOS 12   
Attachments:
Description Flags
Screen recording demonstrating the issue
none
Patch
none
Patch for landing none

Description Jacob Bandes-Storch 2022-01-21 11:05:13 PST 
Created attachment 449672 [details]
Screen recording demonstrating the issue

Also filed as FB9854642

Reading a file with file.stream() is much slower than repeatedly calling file.slice().

1. Visit https://jsfiddle.net/0hnembvu/21/
2. Choose a large file (~200MB). Observe the progress bar updates smoothly, and the file can be read in ~200ms.
3. Reload the page.
4. Enable the "use ReadableStream API" checkbox.
5. Choose the same large file again. Observe the page becomes unresponsive while reading (the progress bar does not update smoothly) and the file takes much longer to read (~1500ms).
Comment 2 Radar WebKit Bug Importer 2022-01-24 10:25:46 PST 
<rdar://problem/87977499>
Comment 3 youenn fablet 2022-01-24 10:25:53 PST 
Created attachment 449827 [details]
Patch
Comment 4 Alex Christensen 2022-01-24 11:22:27 PST 
Comment on attachment 449827 [details]
Patch

View in context: https://bugs.webkit.org/attachment.cgi?id=449827&action=review

> Source/WebCore/fileapi/Blob.cpp:273
>                  return;

This is a little strange.  There is nothing after this now.
Comment 5 youenn fablet 2022-01-24 11:28:08 PST 
Created attachment 449836 [details]
Patch for landing
Comment 6 EWS 2022-01-24 13:13:50 PST 
Committed r288463 (246349@main): <https://commits.webkit.org/246349@main>

All reviewed patches have been landed. Closing bug and clearing flags on attachment 449836 [details].
Comment 7 Jacob Bandes-Storch 2022-01-24 14:28:58 PST 
Amazing turnaround time! :D