Xcode 16.3 repeatedly log causing CPU leak

Developer Tools & Services Xcode
SonaYu
SonaYu OP
Created Apr ’25
Replies 7
Boosts 3
Views 217
Participants 4

Xcode 16.3 repeatedly logs a same message very frequently, as fast as a single thread can. I use Instruments and Console and find out the log is:

Needs flush!

by -[DNTBrotliDecoder decodeBytes:length:] in DNTDocumentationSupport.

The call is on a single non-main thread. I've tried to clear caches and it seems doesn't change. Yet I don't know exact point when the logging starts since launch.

Fortunately, this thread is dispatched at E cores, bringing approximately 2 watts of power load to my Mac.

Environments:

  • macOS 15.4 (24E248)
  • Xcode 16.3 (16E140)
  • M4 chip

Answered by lAppliEnRose in 841120022

Problem solved in Xcode version 16.4 (16F6) available now.

Replies  7
Boosts  3
Views  217
Participants  4
picnicbob
picnicbob OP
Apr ’25

I have the same problem and my documentation indexing always gets stuck at about 15%. I've deleted the entire ~/Library/Developer folder with no change. • macOS 15.4 (24E248) • Xcode 16.3 (16E140) • M4 Pro (14-core) Mac mini

1
SonaYu
SonaYu OP
Apr ’25

Problem persists and behaves in the same way in a fresh macOS 15.5 beta (24F5042g). I used UTM as a Virtualization environment.

bringing approximately 2 watts of power load to my Mac

I'm new to Apple silicon therefore I wrongly measured the power consumption. It seems to be 0.15W ~ 0.2W on M4 and 6W on virtualized M4.

0
lAppliEnRose
lAppliEnRose OP
Apr ’25

Same issue here, when searching in documentation help, all is functional but there is a progress bar at the bottom saying "indexing..." stuck on the left. Activity monitor shows Xcode using 85% CPU. Process is XCode, DNTDocumentationSupport. Output from Console:

default 16:41:51.375813+0200 Xcode Needs flush!

About 20,000 logs per second!

0
SonaYu
SonaYu OP
Apr ’25

Problems gone 16.4 beta (16F1t). Seems working fine on all macOS.

2
henrique
henrique OP
May ’25

Also seeing Needs flush!, but in Console.app.

1
lAppliEnRose
lAppliEnRose OP
May ’25

Quitted Xcode. Removed the Xcode folders:

  • DerivedData
  • DocumentationCache
  • DocumentationIndex

The problem is still there. FeedBack ID: FB17351766

0
lAppliEnRose
lAppliEnRose OP
May ’25
Accepted Answer

Problem solved in Xcode version 16.4 (16F6) available now.

1
Xcode 16.3 repeatedly log causing CPU leak
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