From 43900aed681ae60a1f90cbb70348aa6c95f5a309 Mon Sep 17 00:00:00 2001 From: Joel Rosdahl Date: Mon, 9 Aug 2021 21:40:38 +0200 Subject: [PATCH] doc: Describe interaction between primary and secondary storage --- doc/MANUAL.adoc | 26 ++++++++++++++++++++++++-- 1 file changed, 24 insertions(+), 2 deletions(-) diff --git a/doc/MANUAL.adoc b/doc/MANUAL.adoc index e62194fd9..859ee40e0 100644 --- a/doc/MANUAL.adoc +++ b/doc/MANUAL.adoc @@ -935,7 +935,9 @@ _key_=_value_ or just _key_ as a short form of _key_=*true*. Attribute values must be https://en.wikipedia.org/wiki/Percent-encoding[percent-encoded] if they contain percent, pipe or space characters. -Optional attributes available for all secondary storage backends: +=== Attributes for all backends + +These optional attributes are available for all secondary storage backends: * *read-only*: If *true*, only read from this backend, don't write. The default is *false*. @@ -964,7 +966,27 @@ Examples: * *share-hits*: If *true*, write hits for this backend to primary storage. The default is *true*. -These are the available backends: + +=== Storage interaction + +The table below describes the interaction between primary and secondary storage +on cache hits and misses: + +[options="header",cols="20%,20%,60%"] +|============================================================================== +| *Primary storage* | *Secondary storage* | *What happens* + +| miss | miss | Compile, write to primary, write to secondary^[1]^ +| miss | hit | Read from secondary, write to primary^[2]^ +| hit | - | Read from primary, don't write to secondary^[3]^ + +|============================================================================== + +^[1]^ Unless secondary storage has attribute `read-only=true`. + +^[2]^ Unless secondary storage has attribute `share-hits=false`. + +^[3]^ Unless primary storage is set to share its cache hits with the +<> option. + === File storage backend -- 2.47.2