On 25/02/14 19:28, Andres Freund wrote:
> I think all that's needed is to cut the first paragraphs that generally
> explain what huge pages are in some detail from the text and make sure
> the later paragraphs don't refer to the earlier ones.

Attached you will find a new version of the patch.

Best regards,

 Christian Kruse               http://www.2ndQuadrant.com/
 PostgreSQL Development, 24x7 Support, Training & Services

diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index 4dc1277..0006090 100644
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -1128,10 +1128,7 @@ include 'filename'
         The use of huge TLB pages results in smaller page tables and
         less CPU time spent on memory management, increasing performance. For
         more details, see
-        <ulink url="https://wiki.debian.org/Hugepages";>the Debian wiki</ulink>.
-        Remember that you will need at least shared_buffers / huge page size +
-        1 huge TLB pages. So for example for a system with 6GB shared buffers
-        and a hugepage size of 2kb of you will need at least 3156 huge pages.
+        <xref linkend="linux-huge-tlb-pages">.
diff --git a/doc/src/sgml/runtime.sgml b/doc/src/sgml/runtime.sgml
index bbb808f..f172526 100644
--- a/doc/src/sgml/runtime.sgml
+++ b/doc/src/sgml/runtime.sgml
@@ -1307,6 +1307,55 @@ echo -1000 > /proc/self/oom_score_adj
+  <sect2 id="linux-huge-tlb-pages">
+   <title>Linux huge TLB pages</title>
+   <para>
+    To enable this feature in <productname>PostgreSQL</productname> you need a
+    kernel with <varname>CONFIG_HUGETLBFS=y</varname> and
+    <varname>CONFIG_HUGETLB_PAGE=y</varname>. You also have to tune the system
+    setting <varname>vm.nr_hugepages</varname>. To calculate the number of
+    necessary huge pages start <productname>PostgreSQL</productname> without
+    huge pages enabled and check the <varname>VmPeak</varname> value from the
+    proc filesystem:
+$ <userinput>head -1 /path/to/data/directory/postmaster.pid</userinput>
+$ <userinput>grep ^VmPeak /proc/4170/status</userinput>
+VmPeak:  6490428 kB
+     <literal>6490428</literal> / <literal>2048</literal>
+     (<varname>PAGE_SIZE</varname> is <literal>2MB</literal> in this case) are
+     roughly <literal>3169.154</literal> huge pages, so you will need at
+     least <literal>3170</literal> huge pages:
+$ <userinput>sysctl -w vm.nr_hugepages=3170</userinput>
+    Sometimes the kernel is not able to allocate the desired number of huge
+    pages, so it might be necessary to repeat that command or to reboot. Don't
+    forget to add an entry to <filename>/etc/sysctl.conf</filename> to persist
+    this setting through reboots.
+   </para>
+   <para>
+    The default behavior for huge pages in
+    <productname>PostgreSQL</productname> is to use them when possible and
+    to fallback to normal pages when failing. To enforce the use of huge
+    pages, you can set
+    <link linkend="guc-huge-tlb-pages"><varname>huge_tlb_pages</varname></link>
+    to <literal>on</literal>. Note that in this case
+    <productname>PostgreSQL</productname> will fail to start if not enough huge
+    pages are available.
+   </para>
+   <para>
+    For a detailed description of the <productname>Linux</productname> huge
+    pages feature have a look
+    at <ulink url="https://www.kernel.org/doc/Documentation/vm/hugetlbpage.txt";>https://www.kernel.org/doc/Documentation/vm/hugetlbpage.txt</ulink>.
+   </para>
+  </sect2>

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