Re: doc patch - linux memory handling - Mailing list pgsql-patches

Patch applied.  Thanks.

---------------------------------------------------------------------------


Andrew Dunstan wrote:
>
> It appears we are back in the "you need a non-empty password" mode.
>
> Anyway, here's the revised patch.
>
> andrew
>
>
> Andrew Dunstan wrote:
>
> >
> > I didn't find a single instance of a <warning> tag in the doc sources.
> > I did find a warning in an unadorned para, in func.sgml.
> >
> > Anyway, I made the changes (using <note>) but anoncvs is now refusing
> > my login attempt, so I can't do the diff.
> >
> > I've spent way too much time on this already - really my only concern
> > was that the docs would give people info that would make things worse
> > rather than better, and nobody else was doing anything about it.
> >
> > cheers
> >
> > andrew
> >
>

> Index: doc/src/sgml/runtime.sgml
> ===================================================================
> RCS file: /projects/cvsroot/pgsql-server/doc/src/sgml/runtime.sgml,v
> retrieving revision 1.200
> diff -c -w -r1.200 runtime.sgml
> *** doc/src/sgml/runtime.sgml    17 Aug 2003 22:19:10 -0000    1.200
> --- doc/src/sgml/runtime.sgml    22 Aug 2003 16:14:47 -0000
> ***************
> *** 3068,3081 ****
>          </para>
>
>          <para>
> !         Linux has poor default memory overcommit behavior.  Rather than
> !         failing if it can not reserve enough memory, it returns success,
> !         but later fails when the memory can't be mapped and terminates
> !         the application with <literal>kill -9</>.  To prevent unpredictable
> !         process termination, use:
>   <programlisting>
>   sysctl -w vm.overcommit_memory=3
>   </programlisting>
>           Note, you will need enough swap space to cover all your memory needs.
>          </para>
>         </listitem>
> --- 3068,3128 ----
>          </para>
>
>          <para>
> !     Linux kernel version 2.4.* has poor default memory overcommit
> !     behavior, which can result in the postmaster being killed by the
> !     kernel due to memory demands by another process if the system
> !     runs out of memory.
> !     </para>
> !
> !        <para>
> !     The symptom of this occuring is a kernel message looking like
> !     this (consult your system documentation and configuration on
> !     where to look for such a message):
> ! <programlisting>
> !  Out of Memory: Killed process 12345 (postmaster).
> ! </programlisting>
> !     </para>
> !
> !        <para>
> !     To avoid this situation, run <productname>PostgreSQL</productname>
> !     on a machine where you
> !     can be sure that other processes will not run the machine out
> !     of memory. If your kernel supports strict and/or paranoid modes
> !     of overcommit handling, you can also relieve this problem by
> !     altering the system's default behaviour. This can be determined
> !     by examining the function <function>vm_enough_memory</>
> !     in the file <filename>mm/mmap.c</>in the kernel source.
> !     If this file reveals that strict and/or paranoid modes are
> !     supported by your kernel, turn one of these modes on by using
> ! <programlisting>
> ! sysctl -w vm.overcommit_memory=2
> ! </programlisting>
> !      for strict mode or
>   <programlisting>
>   sysctl -w vm.overcommit_memory=3
>   </programlisting>
> +     for paranoid mode, or placing an equivalent entry in
> +     <filename>/etc/sysctl.conf</>.
> +     </para>
> +
> +        <note>
> +     <para>
> +      Warning: using these settings in a kernel which does not support
> +      these modes will almost certainly increase the danger of the
> +      kernel killing the postmaster, rather than reducing it.
> +      If in any doubt, consult a kernel expert or your kernel vendor.
> +     </para>
> +        </note>
> +
> +        <para>
> +     These modes are expected to be supported in all 2.6 and later
> +     kernels. Some vendor 2.4 kernels may also support these modes.
> +     However, it is known that some vendor documents suggest that
> +     they support them while examination of the kernel source reveals
> +     that they do not.
> +     </para>
> +
> +        <para>
>           Note, you will need enough swap space to cover all your memory needs.
>          </para>
>         </listitem>

>
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