Index: Makefile.in
==================================================================
--- Makefile.in
+++ Makefile.in
@@ -43,10 +43,11 @@
 BCCFLAGS =	@CPPFLAGS@ @CFLAGS@
 TCCFLAGS =	@EXTRA_CFLAGS@ @CPPFLAGS@ @CFLAGS@ -DHAVE_AUTOCONFIG_H -D_HAVE_SQLITE_CONFIG_H
 INSTALLDIR = $(DESTDIR)@prefix@/bin
 USE_SYSTEM_SQLITE = @USE_SYSTEM_SQLITE@
 USE_LINENOISE = @USE_LINENOISE@
+USE_MMAN_H = @USE_MMAN_H@
 USE_SEE = @USE_SEE@
 FOSSIL_ENABLE_MINIZ = @FOSSIL_ENABLE_MINIZ@
 
 include $(SRCDIR)/main.mk
 

Index: auto.def
==================================================================
--- auto.def
+++ auto.def
@@ -15,10 +15,11 @@
     with-th1-hooks=0     => {Enable TH1 hooks for commands and web pages}
     with-tcl:path        => {Enable Tcl integration, with Tcl in the specified path}
     with-tcl-stubs=0     => {Enable Tcl integration via stubs library mechanism}
     with-tcl-private-stubs=0
                          => {Enable Tcl integration via private stubs mechanism}
+    with-mman=0          => {Enable use of POSIX memory APIs from "sys/mman.h"}
     with-see=0           => {Enable the SQLite Encryption Extension (SEE)}
     internal-sqlite=1    => {Don't use the internal SQLite, use the system one}
     static=0             => {Link a static executable}
     fusefs=1             => {Disable the Fuse Filesystem}
     fossil-debug=0       => {Build with fossil debugging enabled}
@@ -40,10 +41,11 @@
 define EXTRA_CFLAGS "-Wall"
 define EXTRA_LDFLAGS ""
 define USE_SYSTEM_SQLITE 0
 define USE_LINENOISE 0
 define FOSSIL_ENABLE_MINIZ 0
+define USE_MMAN_H 0
 define USE_SEE 0
 
 # This procedure is a customized version of "cc-check-function-in-lib",
 # that does not modify the LIBS variable.  Its use prevents prematurely
 # pulling in libraries that will be added later anyhow (e.g. "-ldl").
@@ -141,10 +143,16 @@
 
 if {[opt-bool no-opt]} {
     define CFLAGS {-g -O0 -Wall}
     msg-result "Builting without compiler optimization"
 }
+
+if {[opt-bool with-mman]} {
+    define-append EXTRA_CFLAGS -DUSE_MMAN_H
+    define USE_MMAN_H 1
+    msg-result "Enabling \"sys/mman.h\" support"
+}
 
 if {[opt-bool with-see]} {
     define-append EXTRA_CFLAGS -DUSE_SEE
     define USE_SEE 1
     msg-result "Enabling encryption support"

Index: src/main.c
==================================================================
--- src/main.c
+++ src/main.c
@@ -920,16 +920,20 @@
 #if defined(FOSSIL_ENABLE_TCL)
   int rc;
   const char *zRc;
 #endif
   Stmt q;
+  size_t pageSize = 0;
   blob_zero(pOut);
   blob_appendf(pOut, "This is fossil version %s\n", get_version());
   if( !bVerbose ) return;
   blob_appendf(pOut, "Compiled on %s %s using %s (%d-bit)\n",
                __DATE__, __TIME__, COMPILER_NAME, sizeof(void*)*8);
   blob_appendf(pOut, "Schema version %s\n", AUX_SCHEMA_MAX);
+  fossil_get_page_size(&pageSize);
+  blob_appendf(pOut, "Detected memory page size is %lu bytes\n",
+               (unsigned long)pageSize);
 #if defined(FOSSIL_ENABLE_MINIZ)
   blob_appendf(pOut, "miniz %s, loaded %s\n", MZ_VERSION, mz_version());
 #else
   blob_appendf(pOut, "zlib %s, loaded %s\n", ZLIB_VERSION, zlibVersion());
 #endif
@@ -992,10 +996,13 @@
   blob_append(pOut, "FOSSIL_STATIC_BUILD\n", -1);
 #endif
 #if defined(HAVE_PLEDGE)
   blob_append(pOut, "HAVE_PLEDGE\n", -1);
 #endif
+#if defined(USE_MMAN_H)
+  blob_append(pOut, "USE_MMAN_H\n", -1);
+#endif
 #if defined(USE_SEE)
   blob_append(pOut, "USE_SEE\n", -1);
 #endif
 #if defined(FOSSIL_ALLOW_OUT_OF_ORDER_DATES)
   blob_append(pOut, "FOSSIL_ALLOW_OUT_OF_ORDER_DATES\n");

Index: src/makemake.tcl
==================================================================
--- src/makemake.tcl
+++ src/makemake.tcl
@@ -623,10 +623,14 @@
 # FOSSIL_ENABLE_TCL_PRIVATE_STUBS = 1
 
 #### Use 'system' SQLite
 #
 # USE_SYSTEM_SQLITE = 1
+
+#### Use POSIX memory APIs from "sys/mman.h"
+#
+# USE_MMAN_H = 1
 
 #### Use the SQLite Encryption Extension
 #
 # USE_SEE = 1
 
@@ -860,10 +864,16 @@
 # With JSON support
 ifdef FOSSIL_ENABLE_JSON
 TCC += -DFOSSIL_ENABLE_JSON=1
 RCC += -DFOSSIL_ENABLE_JSON=1
 endif
+
+# With "sys/mman.h" support
+ifdef USE_MMAN_H
+TCC += -DUSE_MMAN_H=1
+RCC += -DUSE_MMAN_H=1
+endif
 
 # With SQLite Encryption Extension support
 ifdef USE_SEE
 TCC += -DUSE_SEE=1
 RCC += -DUSE_SEE=1

Index: src/th_main.c
==================================================================
--- src/th_main.c
+++ src/th_main.c
@@ -749,10 +749,11 @@
 ** "tclPrivateStubs" = FOSSIL_ENABLE_TCL_PRIVATE_STUBS
 ** "json"            = FOSSIL_ENABLE_JSON
 ** "markdown"        = FOSSIL_ENABLE_MARKDOWN
 ** "unicodeCmdLine"  = !BROKEN_MINGW_CMDLINE
 ** "dynamicBuild"    = FOSSIL_DYNAMIC_BUILD
+** "mman"            = USE_MMAN_H
 ** "see"             = USE_SEE
 **
 ** Specifying an unknown feature will return a value of false, it will not
 ** raise a script error.
 */
@@ -829,10 +830,15 @@
 #endif
 #if defined(FOSSIL_DYNAMIC_BUILD)
   else if( 0 == fossil_strnicmp( zArg, "dynamicBuild\0", 13 ) ){
     rc = 1;
   }
+#endif
+#if defined(USE_MMAN_H)
+  else if( 0 == fossil_strnicmp( zArg, "mman\0", 5 ) ){
+    rc = 1;
+  }
 #endif
 #if defined(USE_SEE)
   else if( 0 == fossil_strnicmp( zArg, "see\0", 4 ) ){
     rc = 1;
   }

Index: src/util.c
==================================================================
--- src/util.c
+++ src/util.c
@@ -17,10 +17,14 @@
 **
 ** This file contains code for miscellaneous utility routines.
 */
 #include "config.h"
 #include "util.h"
+#if defined(USE_MMAN_H)
+# include <sys/mman.h>
+# include <unistd.h>
+#endif
 
 /*
 ** For the fossil_timer_xxx() family of functions...
 */
 #ifdef _WIN32
@@ -72,10 +76,12 @@
 #if defined(_WIN32)
   SYSTEM_INFO sysInfo;
   memset(&sysInfo, 0, sizeof(SYSTEM_INFO));
   GetSystemInfo(&sysInfo);
   *piPageSize = (size_t)sysInfo.dwPageSize;
+#elif defined(USE_MMAN_H)
+  *piPageSize = (size_t)sysconf(_SC_PAGE_SIZE);
 #else
   *piPageSize = 4096; /* FIXME: What for POSIX? */
 #endif
 }
 void *fossil_secure_alloc_page(size_t *pN){
@@ -91,10 +97,18 @@
     fossil_fatal("VirtualAlloc failed: %lu\n", GetLastError());
   }
   if( !VirtualLock(p, pageSize) ){
     fossil_fatal("VirtualLock failed: %lu\n", GetLastError());
   }
+#elif defined(USE_MMAN_H)
+  p = mmap(0, pageSize, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0);
+  if( p==MAP_FAILED ){
+    fossil_fatal("mmap failed: %d\n", errno);
+  }
+  if( mlock(p, pageSize) ){
+    fossil_fatal("mlock failed: %d\n", errno);
+  }
 #else
   p = fossil_malloc(pageSize);
 #endif
   fossil_secure_zero(p, pageSize);
   if( pN ) *pN = pageSize;
@@ -109,10 +123,17 @@
     fossil_fatal("VirtualUnlock failed: %lu\n", GetLastError());
   }
   if( !VirtualFree(p, 0, MEM_RELEASE) ){
     fossil_fatal("VirtualFree failed: %lu\n", GetLastError());
   }
+#elif defined(USE_MMAN_H)
+  if( munlock(p, n) ){
+    fossil_fatal("munlock failed: %d\n", errno);
+  }
+  if( munmap(p, n) ){
+    fossil_fatal("munmap failed: %d\n", errno);
+  }
 #else
   fossil_free(p);
 #endif
 }
 

Index: win/Makefile.mingw
==================================================================
--- win/Makefile.mingw
+++ win/Makefile.mingw
@@ -96,10 +96,14 @@
 # FOSSIL_ENABLE_TCL_PRIVATE_STUBS = 1
 
 #### Use 'system' SQLite
 #
 # USE_SYSTEM_SQLITE = 1
+
+#### Use POSIX memory APIs from "sys/mman.h"
+#
+# USE_MMAN_H = 1
 
 #### Use the SQLite Encryption Extension
 #
 # USE_SEE = 1
 
@@ -333,10 +337,16 @@
 # With JSON support
 ifdef FOSSIL_ENABLE_JSON
 TCC += -DFOSSIL_ENABLE_JSON=1
 RCC += -DFOSSIL_ENABLE_JSON=1
 endif
+
+# With "sys/mman.h" support
+ifdef USE_MMAN_H
+TCC += -DUSE_MMAN_H=1
+RCC += -DUSE_MMAN_H=1
+endif
 
 # With SQLite Encryption Extension support
 ifdef USE_SEE
 TCC += -DUSE_SEE=1
 RCC += -DUSE_SEE=1

Index: win/Makefile.mingw.mistachkin
==================================================================
--- win/Makefile.mingw.mistachkin
+++ win/Makefile.mingw.mistachkin
@@ -96,10 +96,14 @@
 FOSSIL_ENABLE_TCL_PRIVATE_STUBS = 1
 
 #### Use 'system' SQLite
 #
 # USE_SYSTEM_SQLITE = 1
+
+#### Use POSIX memory APIs from "sys/mman.h"
+#
+# USE_MMAN_H = 1
 
 #### Use the SQLite Encryption Extension
 #
 # USE_SEE = 1
 
@@ -333,10 +337,16 @@
 # With JSON support
 ifdef FOSSIL_ENABLE_JSON
 TCC += -DFOSSIL_ENABLE_JSON=1
 RCC += -DFOSSIL_ENABLE_JSON=1
 endif
+
+# With "sys/mman.h" support
+ifdef USE_MMAN_H
+TCC += -DUSE_MMAN_H=1
+RCC += -DUSE_MMAN_H=1
+endif
 
 # With SQLite Encryption Extension support
 ifdef USE_SEE
 TCC += -DUSE_SEE=1
 RCC += -DUSE_SEE=1

Index: win/fossil.rc
==================================================================
--- win/fossil.rc
+++ win/fossil.rc
@@ -161,10 +161,15 @@
 #endif /* defined(FOSSIL_ENABLE_TCL_PRIVATE_STUBS) */
 #endif /* defined(FOSSIL_ENABLE_TCL) */
 #if defined(FOSSIL_ENABLE_JSON)
       VALUE "JsonEnabled", "Yes, cson " FOSSIL_JSON_API_VERSION "\0"
 #endif /* defined(FOSSIL_ENABLE_JSON) */
+#if defined(USE_MMAN_H)
+      VALUE "UseMmanEnabled", "Yes\0"
+#else
+      VALUE "UseMmanEnabled", "No\0"
+#endif /* defined(USE_MMAN_H) */
 #if defined(USE_SEE)
       VALUE "UseSeeEnabled", "Yes\0"
 #else
       VALUE "UseSeeEnabled", "No\0"
 #endif /* defined(USE_SEE) */

Index: www/th1.md
==================================================================
--- www/th1.md
+++ www/th1.md
@@ -345,10 +345,11 @@
   1. **tclPrivateStubs** -- _Uses Tcl private stubs (i.e. header-only)._
   1. **json** -- _Support for the JSON APIs._
   1. **markdown** -- _Support for Markdown documentation format._
   1. **unicodeCmdLine** -- _The command line arguments are Unicode._
   1. **dynamicBuild** -- _Dynamically linked to libraries._
+  1. **mman** -- _Uses POSIX memory APIs from "sys/mman.h"._
   1. **see** -- _Uses the SQLite Encryption Extension._
 
 Specifying an unknown feature will return a value of false, it will not
 raise a script error.