Bug 258014

Summary:

Navigation Timing L2 often returns negative timing values for documents served from memory cache

Product:

WebKit

Reporter:

Andy Davies <ad>

Component:

Page Loading

Assignee:

Nobody <webkit-unassigned>

Status:

NEW

Severity:

Normal

CC:

achristensen, beidson, koivisto, webkit-bug-importer

Priority:

Keywords:

InRadar

Version:

Safari 16

Hardware:

iPhone / iPad

OS:

iOS 16

See Also:

https://bugs.webkit.org/show_bug.cgi?id=298443

Attachments:

Description	Flags
Screenshot showing negative NT2 values	none
NT1 calculated values	none

Andy Davies

Reported 2023-06-13 04:03:10 PDT

Created attachment 466677 [details] Screenshot showing negative NT2 values Description: Navigation Level 2 API returns negative values for several metrics when the document is served from memory cache. Behaviour doesn't happen 100% of the time but seems common enough to make it easy to reproduce. Behaviours hasn't been reproduced when document comes from the network, or the disk cache. When there are negative values in NT2, the values calculated via NT1 appear to be reasonable Negative values appear to be constrained to: Reproduction: - Open speedcurve.com - Navigate between a couple of pages until the Inspector shows the document has been loaded from memory cache - Query the NT2 API i.e. performance.getEntriesByType('navigation')[0]; - Observe negative values (steps 2 & 3 might need repeating a few times) Notes: Tested on iPhone with iOS 16.5, Safari 16.5 (17615.2.9.11.6, 17615) and STP 171 (Safari 16.4, WebKit 17616.1.15) running on Intel Mac

Attachments
Screenshot showing negative NT2 values (246.94 KB, image/png) 2023-06-13 04:03 PDT, Andy Davies	no flags	Details
NT1 calculated values (225.33 KB, image/png) 2023-06-13 04:04 PDT, Andy Davies	no flags	Details
View All Add attachment proposed patch, testcase, etc.

Andy Davies

Comment 1 2023-06-13 04:04:01 PDT

Created attachment 466678 [details] NT1 calculated values

Radar WebKit Bug Importer

Comment 2 2023-06-20 04:04:16 PDT

<rdar://problem/111032230>

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