[wp-trac] [WordPress Trac] #60011: 6.4.1 seems to deliver poor external cache performance compared with 6.3.2

[WordPress Trac]

#60011: 6.4.1 seems to deliver poor external cache performance compared with 6.3.2
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 Reporter:  bjornha       |      Owner:  (none)
     Type:  defect (bug)  |     Status:  new
 Priority:  normal        |  Milestone:  Awaiting Review
Component:  Cache API     |    Version:  trunk
 Severity:  normal        |   Keywords:
  Focuses:                |
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 Hello,

 After upgrading WordPress from 6.3.2 to 6.4.1 I noticed a performance
 degradation and started to investigate. The upgrade was done on our
 staging site, where as the production site still runs on 6.3.2

 I went through all plug-ins and made sure that staging and production had
 the same code base and system running except for the WordPress versions.

 We use Redis version 6 as central cache for our sites, that all run on 2
 instances in Azure Web Services for Linux, using PHP 8.2 as base.
 The cache miss rate has constantly been ~10% on version 6.3.2 but
 increased to ~34% on version 6.4.1.

 I have run the two setups side by side over the weekend and had a similar
 load on the sites and the figures above seem consistent over time.

 I have nothing more specific to share as to which lookups that fail, but
 it seems consistent over WordPress and plug-ins using the external cache.

 I have had a look on Pods behavior together with Pods support as I at
 first after upgrading saw a 1000% increased page load time and Pods was
 generating most of it. At this point the cache showed a missrate of >70%.

 But after saving Pods settings in 6.4.1, the update of alloptions seemed
 to get rid of that specific overhead and Pods were performing as the rest
 of the plug-ins.

 This is how I realized that the increased load time in 6.4.1 might be
 cache related as the miss rate did not go below 30%.

 As stated above, I have no firm examples of erroneous calls to share, it
 seems to be a general behavior.

 I am also attaching a link to an image showing Redis cache behavior with
 6.3.2 on top, 6.4.1 below.

 If Cache API is the right component for this, I dont know, but it seemed
 to be close to my obeservaton.

 Kind regards,
 Bjørn Hasselberg

 [[Image(https://pro4uadmin.blob.core.windows.net/wordpress/6.3.2%20and%206.4.1%20cache.png)]]

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Ticket URL: <https://core.trac.wordpress.org/ticket/60011>
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