Remove --with-lg-tiny-min.

This option isn't useful in practice.

This partially resolves #580.

INSTALL

@@ -233,38 +233,17 @@ any of the following arguments (not a definitive list) to 'configure':
     This setting is architecture-specific, and although jemalloc includes known
     safe values for the most commonly used modern architectures, there is a
     wrinkle related to GNU libc (glibc) that may impact your choice of
-    <lg-quantum>.  On most modern architectures, this mandates 16-byte alignment
+    <lg-quantum>.  On most modern architectures, this mandates 16-byte
-    (<lg-quantum>=4), but the glibc developers chose not to meet this
+    alignment (<lg-quantum>=4), but the glibc developers chose not to meet this
     requirement for performance reasons.  An old discussion can be found at
     https://sourceware.org/bugzilla/show_bug.cgi?id=206 .  Unlike glibc,
     jemalloc does follow the C standard by default (caveat: jemalloc
-    technically cheats if --with-lg-tiny-min is smaller than
+    technically cheats for size classes smaller than the quantum), but the fact
-    --with-lg-quantum), but the fact that Linux systems already work around
+    that Linux systems already work around this allocator noncompliance means
-    this allocator noncompliance means that it is generally safe in practice to
+    that it is generally safe in practice to let jemalloc's minimum alignment
-    let jemalloc's minimum alignment follow glibc's lead.  If you specify
+    follow glibc's lead.  If you specify --with-lg-quantum=3 during
-    --with-lg-quantum=3 during configuration, jemalloc will provide additional
+    configuration, jemalloc will provide additional size classes that are not
-    size classes that are not 16-byte-aligned (24, 40, and 56).
+    16-byte-aligned (24, 40, and 56).
-
---with-lg-tiny-min=<lg-tiny-min>
-    Specify the base 2 log of the minimum tiny size class to support.  Tiny
-    size classes are powers of 2 less than the quantum, and are only
-    incorporated if <lg-tiny-min> is less than <lg-quantum> (see
-    --with-lg-quantum).  Tiny size classes technically violate the C standard
-    requirement for minimum alignment, and crashes could conceivably result if
-    the compiler were to generate instructions that made alignment assumptions,
-    both because illegal instruction traps could result, and because accesses
-    could straddle page boundaries and cause segmentation faults due to
-    accessing unmapped addresses.
-
-    The default of <lg-tiny-min>=3 works well in practice even on architectures
-    that technically require 16-byte alignment, probably for the same reason
-    --with-lg-quantum=3 works.  Smaller tiny size classes can, and will, cause
-    crashes (see https://bugzilla.mozilla.org/show_bug.cgi?id=691003 for an
-    example).
-
-    This option is rarely useful, and is mainly provided as documentation of a
-    subtle implementation detail.  If you do use this option, specify a
-    value in [3, ..., <lg-quantum>].
 
 The following environment variables (not a definitive list) impact configure's
 behavior:

configure.ac

@@ -1296,13 +1296,6 @@ else
   fi
 fi
 
-AC_ARG_WITH([lg_tiny_min],
-  [AS_HELP_STRING([--with-lg-tiny-min=<lg-tiny-min>],
-   [Base 2 log of minimum tiny size class to support])],
-  [LG_TINY_MIN="$with_lg_tiny_min"],
-  [LG_TINY_MIN="3"])
-AC_DEFINE_UNQUOTED([LG_TINY_MIN], [$LG_TINY_MIN])
-
 AC_ARG_WITH([lg_quantum],
   [AS_HELP_STRING([--with-lg-quantum=<lg-quantum>],
    [Base 2 log of minimum allocation alignment])],
@@ -2016,13 +2009,12 @@ AC_CONFIG_COMMANDS([include/jemalloc/internal/public_unnamespace.h], [
 ])
 AC_CONFIG_COMMANDS([include/jemalloc/internal/size_classes.h], [
   mkdir -p "${objroot}include/jemalloc/internal"
-  "${SHELL}" "${srcdir}/include/jemalloc/internal/size_classes.sh" "${LG_QUANTA}" ${LG_TINY_MIN} "${LG_PAGE_SIZES}" 2 > "${objroot}include/jemalloc/internal/size_classes.h"
+  "${SHELL}" "${srcdir}/include/jemalloc/internal/size_classes.sh" "${LG_QUANTA}" 3 "${LG_PAGE_SIZES}" 2 > "${objroot}include/jemalloc/internal/size_classes.h"
 ], [
   SHELL="${SHELL}"
   srcdir="${srcdir}"
   objroot="${objroot}"
   LG_QUANTA="${LG_QUANTA}"
-  LG_TINY_MIN=${LG_TINY_MIN}
   LG_PAGE_SIZES="${LG_PAGE_SIZES}"
 ])
 AC_CONFIG_COMMANDS([include/jemalloc/jemalloc_protos_jet.h], [

include/jemalloc/internal/jemalloc_internal_defs.h.in

@@ -172,9 +172,6 @@
 /* Support lazy locking (avoid locking unless a second thread is launched). */
 #undef JEMALLOC_LAZY_LOCK
 
-/* Minimum size class to support is 2^LG_TINY_MIN bytes. */
-#undef LG_TINY_MIN
-
 /*
  * Minimum allocation alignment is 2^LG_QUANTUM bytes (ignoring tiny size
  * classes).

include/jemalloc/internal/size_classes.sh

@@ -285,6 +285,7 @@ cat <<EOF
  * This header file defines:
  *
  *   LG_SIZE_CLASS_GROUP: Lg of size class count for each size doubling.
+ *   LG_TINY_MIN: Lg of minimum size class to support.
  *   SIZE_CLASSES: Complete table of SC(index, lg_grp, lg_delta, ndelta, psz,
  *                 bin, pgs, lg_delta_lookup) tuples.
  *     index: Size class index.
@@ -310,6 +311,7 @@ cat <<EOF
  */
 
 #define LG_SIZE_CLASS_GROUP	${lg_g}
+#define LG_TINY_MIN		${lg_tmin}
 
 EOF