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Date: Tue, 16 Oct 2018 11:38:20 -0400
From: Bruce Momjian <bruce@momjian.us>
To: nat@makarevitch.org, pgsql-docs@lists.postgresql.org
Subject: Re: effective_cache_size
Message-ID: <20181016153820.GD31154@momjian.us>
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 <20181011174849.GC7807@momjian.us>
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On Thu, Oct 11, 2018 at 01:48:49PM -0400, Bruce Momjian wrote:
> So, I think there are two action items here.  First, rename "disk" to
> "drive" or "storage" in the docs and server variable descriptions. 
> Second, unify the description of effective_cache_size to talk about
> storage cache size, not just kernel storage cache, and maybe even talk
> about the double buffering effect.

I have attached a patch for the second item, which I would like to
backpatch.  I don't think I want to deal with all the "disk" mentions at
this time.

-- 
  Bruce Momjian  <bruce@momjian.us>        http://momjian.us
  EnterpriseDB                             http://enterprisedb.com

+ As you are, so once was I.  As I am, so you will be. +
+                      Ancient Roman grave inscription +

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diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index 7554cba..b8e32d7 100644
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -4147,7 +4147,8 @@ ANY <replaceable class="parameter">num_sync</replaceable> ( <replaceable class="
         used. When setting this parameter you should consider both
         <productname>PostgreSQL</productname>'s shared buffers and the
         portion of the kernel's disk cache that will be used for
-        <productname>PostgreSQL</productname> data files.  Also, take
+        <productname>PostgreSQL</productname> data files, though some
+        data might exist in both places. Also, take
         into account the expected number of concurrent queries on different
         tables, since they will have to share the available
         space.  This parameter has no effect on the size of shared
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index 2317e8b..e471d7f 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -2987,10 +2987,9 @@ static struct config_int ConfigureNamesInt[] =
 
 	{
 		{"effective_cache_size", PGC_USERSET, QUERY_TUNING_COST,
-			gettext_noop("Sets the planner's assumption about the size of the disk cache."),
-			gettext_noop("That is, the portion of the kernel's disk cache that "
-						 "will be used for PostgreSQL data files. This is measured in disk "
-						 "pages, which are normally 8 kB each."),
+			gettext_noop("Sets the planner's assumption about the size of the data cache."),
+			gettext_noop("That is, the size of the cache used for PostgreSQL data files. "
+						 "This is measured in disk pages, which are normally 8 kB each."),
 			GUC_UNIT_BLOCKS,
 		},
 		&effective_cache_size,

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