Re: [HACKERS] loading libraries on Postmaster startup - Mailing list pgsql-patches

Your patch has been added to the PostgreSQL unapplied patches list at:

    http://momjian.postgresql.org/cgi-bin/pgpatches

I will try to apply it within the next 48 hours.

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


Joe Conway wrote:
> Joe Conway wrote:
> > Tom Lane wrote:
> >> Joe Conway <mail@joeconway.com> writes:
> >>> In my testing with PL/R, it reduces the first call to a PL/R function
> >>> (after connecting) from almost 2 seconds, down to about 8 ms.
> >>
> >> Hm, pretty significant.  Can you measure any per-fork cost (ie, the loss
> >> incurred by children that don't use PL/R)?  Is there any measurable
> >> benefit for our other PLs (plperl etc)?
> >
> > Here's what I got:
> >
> > 10000 connect/disconnect in tight loop
> > ----------------------------------------------------------
> > condition        time        top
> > ----------------------------------------------------------
> > with no preload        87 seconds    ~10% CPU, ~2.2 MB
> > with plr preload    133 seconds    ~10% CPU, ~13 MB
> > with plperl preload    92 seconds    ~10% CPU, ~3.2 MB
> > with pltcl preload    88 seconds    ~10% CPU, ~2.3 MB
> > with plpython preload    93 seconds    ~10% CPU, ~2.3 MB
> >
> >
> > 1000 connect/"select some_simple_func()"/disconnect in tight loop
> > ------------------------------------------------------------------
> > condition            time            top
> > ------------------------------------------------------------------
> > plr-func without preload    739 seconds    ~60% CPU, ~13 MB
> > plr-func with preload        26 seconds    ~10% CPU, ~13 MB
> > plperl-func without preload    46 seconds    ~4% CPU, ~3.2 MB
> > plperl-func with preload    33 seconds    ~3% CPU, ~3.2 MB
> > pltcl-func without preload    22 seconds    ~5% CPU, ~2.3 MB
> > pltcl-func with preload        17 seconds    ~4% CPU, ~2.3 MB
> > plpython-func without preload    33 seconds    ~4% CPU, ~2.3 MB
> > plpython-func with preload    31 seconds    ~4% CPU, ~2.3 MB
> >
>
> Here's an updated copy of the patch. The original patch was failing due
> to code drift in cvs.
>
> Peter's suggestion (__attribute__((constructor))) is interesting, but it
> appears to be a gcc specific extension, and hence non-portable.
>
> I'd still like to see this applied if there are no other objections.
>  From the above info it is apparent that the benefit outweighs the cost
> for plperl and pltcl (although not as significantly as for plr).
>
> Joe

> Index: doc/src/sgml/runtime.sgml
> ===================================================================
> RCS file: /opt/src/cvs/pgsql-server/doc/src/sgml/runtime.sgml,v
> retrieving revision 1.169
> diff -c -r1.169 runtime.sgml
> *** doc/src/sgml/runtime.sgml    19 Feb 2003 04:06:28 -0000    1.169
> --- doc/src/sgml/runtime.sgml    27 Feb 2003 18:46:39 -0000
> ***************
> *** 1781,1786 ****
> --- 1781,1815 ----
>        </varlistentry>
>
>        <varlistentry>
> +       <term><varname>PRELOAD_LIBRARIES</varname> (<type>string</type>)</term>
> +       <indexterm><primary>preload_libraries</></>
> +       <listitem>
> +        <para>
> +         This variable specifies one or more shared libraries that are to be
> +     preloaded at Postmaster start. An initialization function can also be
> +     optionally specified by adding a colon followed by the name of the
> +     initialization function after the library name. For example
> +     <literal>'$libdir/mylib:init_mylib'</literal> would cause <literal>mylib</>
> +     to be preloaded and <literal>init_mylib</> to be executed. If more than
> +     one library is to be loaded, they must be delimited with a comma.
> +        </para>
> +
> +        <para>
> +         If <literal>mylib</> is not found, the postmaster will fail to start.
> +     However, if <literal>init_mylib</> is not found, <literal>mylib</> will
> +     still be preloaded without executing the initialization function.
> +        </para>
> +
> +        <para>
> +         By preloading a shared library (and initializing it if applicable),
> +     the library startup time is avoided when the library is used later in a
> +     specific backend. However there is a cost in terms of memory duplication
> +     as every backend is forked, whether or not the library is used.
> +        </para>
> +       </listitem>
> +      </varlistentry>
> +
> +      <varlistentry>
>         <term><varname>REGEX_FLAVOR</varname> (<type>string</type>)</term>
>         <indexterm><primary>regular expressions</></>
>         <listitem>
> Index: src/backend/postmaster/postmaster.c
> ===================================================================
> RCS file: /opt/src/cvs/pgsql-server/src/backend/postmaster/postmaster.c,v
> retrieving revision 1.307
> diff -c -r1.307 postmaster.c
> *** src/backend/postmaster/postmaster.c    23 Feb 2003 04:48:19 -0000    1.307
> --- src/backend/postmaster/postmaster.c    27 Feb 2003 18:46:39 -0000
> ***************
> *** 205,210 ****
> --- 205,212 ----
>   bool        Log_connections = false;
>   bool        Db_user_namespace = false;
>
> + /* list of library:init-function to be preloaded */
> + char       *preload_libraries_string = NULL;
>
>   /* Startup/shutdown state */
>   static pid_t StartupPID = 0,
> ***************
> *** 644,649 ****
> --- 646,658 ----
>       if (EnableSSL)
>           secure_initialize();
>   #endif
> +
> +     /*
> +      * process any libraries that should be preloaded and
> +      * optionally pre-initialized
> +      */
> +     if (preload_libraries_string)
> +         process_preload_libraries(preload_libraries_string);
>
>       /*
>        * Fork away from controlling terminal, if -S specified.
> Index: src/backend/utils/init/miscinit.c
> ===================================================================
> RCS file: /opt/src/cvs/pgsql-server/src/backend/utils/init/miscinit.c,v
> retrieving revision 1.100
> diff -c -r1.100 miscinit.c
> *** src/backend/utils/init/miscinit.c    27 Jan 2003 00:51:06 -0000    1.100
> --- src/backend/utils/init/miscinit.c    27 Feb 2003 18:46:39 -0000
> ***************
> *** 1044,1046 ****
> --- 1044,1135 ----
>                "which is not compatible with this version %s.",
>                file_major, file_minor, version_string);
>   }
> +
> + /*-------------------------------------------------------------------------
> +  *                Library preload support
> +  *-------------------------------------------------------------------------
> +  */
> +
> + #if defined(__mc68000__) && defined(__ELF__)
> + typedef int32 ((*func_ptr) ());
> + #else
> + typedef char *((*func_ptr) ());
> + #endif
> +
> + /*
> +  * process any libraries that should be preloaded and
> +  * optionally pre-initialized
> +  */
> + void
> + process_preload_libraries(char *preload_libraries_string)
> + {
> +     char       *rawstring;
> +     List       *elemlist;
> +     List       *l;
> +
> +     if (preload_libraries_string == NULL)
> +         return;
> +
> +     /* Need a modifiable copy of string */
> +     rawstring = pstrdup(preload_libraries_string);
> +
> +     /* Parse string into list of identifiers */
> +     if (!SplitIdentifierString(rawstring, ',', &elemlist))
> +     {
> +         /* syntax error in list */
> +         pfree(rawstring);
> +         freeList(elemlist);
> +         elog(LOG, "invalid list syntax for preload_libraries configuration option");
> +     }
> +
> +     foreach(l, elemlist)
> +     {
> +         char       *tok = (char *) lfirst(l);
> +         char       *sep = strstr(tok, ":");
> +         char       *filename = NULL;
> +         char       *funcname = NULL;
> +         func_ptr    initfunc;
> +
> +         if (sep)
> +         {
> +             /*
> +              * a colon separator implies there is an initialization function
> +              * that we need to run in addition to loading the library
> +              */
> +             size_t        filename_len = sep - tok;
> +             size_t        funcname_len = strlen(tok) - filename_len - 1;
> +
> +             filename = (char *) palloc(filename_len + 1);
> +             memset(filename, '\0', filename_len + 1);
> +             snprintf(filename, filename_len + 1, "%s", tok);
> +
> +             funcname = (char *) palloc(funcname_len + 1);
> +             memset(funcname, '\0', funcname_len + 1);
> +             snprintf(funcname, funcname_len + 1, "%s", sep + 1);
> +         }
> +         else
> +         {
> +             /*
> +              * no separator -- just load the library
> +              */
> +             filename = pstrdup(tok);
> +             funcname = NULL;
> +         }
> +
> +         initfunc = (func_ptr) load_external_function(filename, funcname, false, NULL);
> +         if (initfunc)
> +             (*initfunc)();
> +
> +         elog(LOG, "preloaded library %s with initialization function %s", filename, funcname);
> +
> +         if (filename != NULL)
> +             pfree(filename);
> +
> +         if (funcname != NULL)
> +             pfree(funcname);
> +     }
> +
> +     pfree(rawstring);
> +     freeList(elemlist);
> + }
> +
> Index: src/backend/utils/misc/guc.c
> ===================================================================
> RCS file: /opt/src/cvs/pgsql-server/src/backend/utils/misc/guc.c,v
> retrieving revision 1.115
> diff -c -r1.115 guc.c
> *** src/backend/utils/misc/guc.c    23 Feb 2003 23:27:21 -0000    1.115
> --- src/backend/utils/misc/guc.c    27 Feb 2003 18:46:39 -0000
> ***************
> *** 60,65 ****
> --- 60,66 ----
>   extern bool autocommit;
>   extern int    CommitDelay;
>   extern int    CommitSiblings;
> + extern char *preload_libraries_string;
>
>   #ifdef HAVE_SYSLOG
>   extern char *Syslog_facility;
> ***************
> *** 812,817 ****
> --- 813,824 ----
>       {
>           {"lc_time", PGC_USERSET}, &locale_time,
>           "C", locale_time_assign, NULL
> +     },
> +
> +     {
> +         {"preload_libraries", PGC_POSTMASTER, GUC_LIST_INPUT | GUC_LIST_QUOTE},
> +         &preload_libraries_string,
> +         "", NULL, NULL
>       },
>
>       {
> Index: src/backend/utils/misc/postgresql.conf.sample
> ===================================================================
> RCS file: /opt/src/cvs/pgsql-server/src/backend/utils/misc/postgresql.conf.sample,v
> retrieving revision 1.70
> diff -c -r1.70 postgresql.conf.sample
> *** src/backend/utils/misc/postgresql.conf.sample    6 Feb 2003 20:25:33 -0000    1.70
> --- src/backend/utils/misc/postgresql.conf.sample    27 Feb 2003 18:46:39 -0000
> ***************
> *** 213,216 ****
> --- 213,217 ----
>   #transform_null_equals = false
>   #statement_timeout = 0        # 0 is disabled, in milliseconds
>   #db_user_namespace = false
> + #preload_libraries = ''
>
> Index: src/include/miscadmin.h
> ===================================================================
> RCS file: /opt/src/cvs/pgsql-server/src/include/miscadmin.h,v
> retrieving revision 1.116
> diff -c -r1.116 miscadmin.h
> *** src/include/miscadmin.h    22 Feb 2003 05:57:45 -0000    1.116
> --- src/include/miscadmin.h    27 Feb 2003 18:46:39 -0000
> ***************
> *** 288,293 ****
> --- 288,294 ----
>                                unsigned long id2);
>
>   extern void ValidatePgVersion(const char *path);
> + extern void process_preload_libraries(char *preload_libraries_string);
>
>   /* these externs do not belong here... */
>   extern void IgnoreSystemIndexes(bool mode);

>
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