With a fresh Sitecore 9.1 installation, we were seeing thousands of these errors in the logs:
WARN AccessResultCache cache is cleared by Sitecore.Caching.Generics.Cache`1+DefaultScavengeStrategy[[Sitecore.Caching.AccessResultCacheKey, Sitecore.Kernel, Version=22.214.171.124, Culture=neutral, PublicKeyToken=null]] strategy. Cache running size was 9 MB.
As mentioned in the warning, the default cache size was used: "Cache running size was 9 MB". That was clearly too small for our environments, so cache size tuning was needed.
The related setting is the following:
<setting name="Caching.AccessResultCacheSize" value="9MB" />
So we created a patch file to increase the size to 200MB:
<configuration xmlns:patch="http://www.sitecore.net/xmlconfig/" xmlns:role="http://www.sitecore.net/xmlconfig/role/" xmlns:set="http://www.sitecore.net/xmlconfig/set/">
<sitecore role:require="Standalone or ContentDelivery or ContentManagement">
<setting name="Caching.AccessResultCacheSize" value="200MB" />
Deployed the patch to the app services and the errors have disappeared, and there was also a noticable performance increase.
Do you have any Sitecore tips or tricks to share? Please send them along!