From: Alex Rousskov <rousskov@measurement-factory.com>
Date: Fri, 9 Sep 2011 17:42:35 +0000 (-0600)
Subject: Provided more documentation for memory_cache_shared, including DEFAULT_DOC.
X-Git-Tag: take08~18
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=70f856bc9c29079fee3ab8dd9f55c3b23c177a11;p=thirdparty%2Fsquid.git

Provided more documentation for memory_cache_shared, including DEFAULT_DOC.
---

diff --git a/src/cf.data.pre b/src/cf.data.pre
index 7d7a432a76..d2adc20bdb 100644
--- a/src/cf.data.pre
+++ b/src/cf.data.pre
@@ -2579,13 +2579,27 @@ COMMENT: on|off
 TYPE: YesNoNone
 LOC: Config.memShared
 DEFAULT: none
+DEFAULT_DOC: "on" where supported if doing memory caching with multiple SMP workers.
 DOC_START
 	Controls whether the memory cache is shared among SMP workers.
 
+	The shared memory cache is meant to occupy cache_mem bytes and replace
+	the non-shared memory cache, although some entities may still be
+	cached locally by workers for now (e.g., internal and in-transit
+	objects may be served from a local memory cache even if shared memory
+	caching is enabled).
+
 	By default, the memory cache is shared if and only if all of the
-	following conditions are satisfied: SMP mode is enabled using multiple
-	worker processes, cache_mem is positive, and Squid was built with a
-	compiler that supports GCC-style atomic operations.
+	following conditions are satisfied: Squid runs in SMP mode with
+	multiple workers, cache_mem is positive, and Squid environment
+	supports required IPC primitives (e.g., POSIX shared memory segments
+	and GCC-style atomic operations).
+
+	To avoid blocking locks, shared memory uses opportunistic algorithms
+	that do not guarantee that every cachable entity that could have been
+	shared among SMP workers will actually be shared.
+
+	Currently, entities exceeding 32KB in size cannot be shared.
 DOC_END
 
 NAME: memory_cache_mode