There seems to be a performance regression in 5.8+ versions of RCS.

RCS consults env var ‘RCS_MEM_LIMIT’ to determine whether or not to fall

back to (slow) stdio mode (which uses temporary files) from the default

in-memory (mmap et al) mode. The default value is "256" (kilobytes), which

is probably too low these days on most workstations. 

RHBZ#1036527

Upstream: https://savannah.gnu.org/bugs/index.php?40200

diff -U0 rcs-5.9.0/ChangeLog.coperf rcs-5.9.0/ChangeLog

--- rcs-5.9.0/ChangeLog.coperf	2013-12-03 13:33:59.544075057 +0100

+++ rcs-5.9.0/ChangeLog	2013-12-03 13:38:42.814534824 +0100

@@ -0,0 +1,7 @@

+2013-10-20  Thien-Thi Nguyen  <ttn@gnu.org>

+

+	Relax RCS_MEM_LIMIT default; fall back if unspecified.

+

+	* doc/rcs.texi (Environment): Update ‘RCS_MEM_LIMIT’ description;

+	add a willful ignorance hint and speculation on its removal.

+

diff -up rcs-5.9.0/doc/rcs.texi.coperf rcs-5.9.0/doc/rcs.texi

--- rcs-5.9.0/doc/rcs.texi.coperf	2013-05-06 10:29:41.000000000 +0200

+++ rcs-5.9.0/doc/rcs.texi	2013-12-03 13:33:59.545075058 +0100

@@ -1002,12 +1002,20 @@ the rest of the command-line.  The effec

 @cindex memory limit

 Normally, for speed, commands either memory map or copy into memory

 the @repo{} if its size is less than the @dfn{memory limit}, currently

-defaulting to 256 kilobytes.  Otherwise the commands fall back to using

+defaulting to ``unlimited''.

+Otherwise (or if the initially-tried speedy ways fail),

+the commands fall back to using

 standard i/o routines.

 You can adjust the memory limit by setting the @samp{RCS_MEM_LIMIT}

 environment variable to a numeric value (measured in kilobytes).

 An empty value is silently ignored.

+

+As a side effect, specifying the memory limit inhibits

+fall-back to slower routines.

+(This env var is mostly intended for testing RCS;

+normally, you can leave it unset.  Probably it will be

+removed in a future release.)

 @end defvr

 @defvr {Environment Variable} TMPDIR

diff -up rcs-5.9.0/src/base.h.coperf rcs-5.9.0/src/base.h

--- rcs-5.9.0/src/base.h.coperf	2013-05-03 10:25:05.000000000 +0200

+++ rcs-5.9.0/src/base.h	2013-12-03 13:33:59.548075060 +0100

@@ -522,6 +522,7 @@ struct behavior

      (if mmap(2)), or operate on a copy of it in core (if no mmap(2)).

      Otherwise, use standard i/o routines as the fallback.

      Set by env var ‘RCS_MEM_LIMIT’.

+     See also ‘MEMORY_UNLIMITED’.

      -- gnurcs_init  */

   struct sff *sff;

@@ -861,6 +862,8 @@ int getRCSINIT (int argc, char **argv, c

 /* Idioms.  */

+#define MEMORY_UNLIMITED  -1

+

 #define BOG_DIFF   (TYAG_TEMPUNLINK | TYAG_DIFF)

 #define BOG_ZONK   (TYAG_DIRTMPUNLINK | TYAG_TEMPUNLINK)

 #define BOG_FULL   (TYAG_ORCSERROR | BOG_ZONK)

diff -up rcs-5.9.0/src/b-fro.c.coperf rcs-5.9.0/src/b-fro.c

--- rcs-5.9.0/src/b-fro.c.coperf	2013-04-30 17:52:07.000000000 +0200

+++ rcs-5.9.0/src/b-fro.c	2013-12-03 13:37:07.237305286 +0100

@@ -61,6 +61,7 @@ fro_open (char const *name, char const *

                            | (strchr (type, 'b') ? OPEN_O_BINARY : 0)

 #endif

                            ));

+  bool unlimited = MEMORY_UNLIMITED == BE (mem_limit);

   if (PROB (fd))

     return NULL;

@@ -81,12 +82,25 @@ fro_open (char const *name, char const *

   f->end = s;

   /* Determine the read method.  */

-  f->rm = status->st_size < 1024 * BE (mem_limit)

+  f->rm = (unlimited

+           || status->st_size < 1024 * BE (mem_limit))

     ? (MMAP_SIGNAL && status->st_size

        ? RM_MMAP

        : RM_MEM)

     : RM_STDIO;

+#define STUBBORNLY_RETRY_MAYBE(METHOD)  do      \

+    {                                           \

+      if (unlimited)                            \

+        {                                       \

+          f->rm = METHOD;                       \

+          goto retry;                           \

+        }                                       \

+      fatal_sys (name);                         \

+    }                                           \

+  while (0)

+

+ retry:

   switch (f->rm)

     {

     case RM_MMAP:

@@ -98,7 +112,7 @@ fro_open (char const *name, char const *

       ISR_DO (CATCHMMAPINTS);

       f->base = mmap (NULL, s, PROT_READ, MAP_SHARED, fd, 0);

       if (f->base == MAP_FAILED)

-        fatal_sys (name);

+        STUBBORNLY_RETRY_MAYBE (RM_MEM);

       /* On many hosts, the superuser can mmap an NFS file

          it can't read.  So access the first page now, and

          print a nice message if a bus error occurs.  */

@@ -131,7 +145,7 @@ fro_open (char const *name, char const *

           do

             {

               if (PROB (r = read (fd, bufptr, bufsiz)))

-                fatal_sys (name);

+                STUBBORNLY_RETRY_MAYBE (RM_STDIO);

               if (!r)

                 {

@@ -147,7 +161,7 @@ fro_open (char const *name, char const *

             }

           while (bufsiz);

           if (PROB (lseek (fd, 0, SEEK_SET)))

-            fatal_sys (name);

+            STUBBORNLY_RETRY_MAYBE (RM_STDIO);

         }

       f->ptr = f->base;

       f->lim = f->base + s;

@@ -162,6 +176,8 @@ fro_open (char const *name, char const *

   f->fd = fd;

   return f;

+

+#undef STUBBORNLY_RETRY_MAYBE

 }

 void

diff -U0 rcs-5.9.0/src/ChangeLog.coperf rcs-5.9.0/src/ChangeLog

--- rcs-5.9.0/src/ChangeLog.coperf	2013-12-03 13:33:59.547075059 +0100

+++ rcs-5.9.0/src/ChangeLog	2013-12-03 13:38:52.305555851 +0100

@@ -0,0 +1,12 @@

+2013-10-20  Thien-Thi Nguyen  <ttn@gnu.org>

+

+	Relax RCS_MEM_LIMIT default; fall back if unspecified.

+

+	* base.h (MEMORY_UNLIMITED): New #define.	

+	* rcsutil.c (gnurcs_init): If unspecified,

+	default ‘BE (mem_limit)’ to ‘MEMORY_UNLIMITED’.

+	* b-fro.c (fro_open): Notice ‘MEMORY_UNLIMITED’ mem limit;

+	in that case, don't check file size, and on ‘RM_MMAP’ or

+	‘RM_MEM’ failure, retry w/ the "next" method: ‘RM_MEM’ or

+	‘RM_STDIO’, respectively.

+

diff -up rcs-5.9.0/src/rcsutil.c.coperf rcs-5.9.0/src/rcsutil.c

--- rcs-5.9.0/src/rcsutil.c.coperf	2013-05-03 13:52:56.000000000 +0200

+++ rcs-5.9.0/src/rcsutil.c	2013-12-03 13:33:59.548075060 +0100

@@ -103,7 +103,7 @@ gnurcs_init (struct program const *progr

          ? 0

          : lim)

       /* Default value.  */

-      : 256;

+      : MEMORY_UNLIMITED;

   }

 }

diff -up rcs-5.9.0/THANKS.coperf rcs-5.9.0/THANKS

--- rcs-5.9.0/THANKS.coperf	2013-12-03 13:33:59.544075057 +0100

+++ rcs-5.9.0/THANKS	2013-12-03 13:34:57.565111763 +0100

@@ -47,4 +47,5 @@ and reporting bugs (sometimes with fixes

   Jiri Moskovcak

   James Olin Oden

   Derek McEachern

+  Andrew J. Schorr

   (and others who prefer anonymity)