commit cb89ba9c72f66327f5d66034681eb1d46eedf96f

Author: DJ Delorie <dj@redhat.com>

Date:   Thu Aug 8 19:09:43 2019 -0400

    Add glibc.malloc.mxfast tunable

    * elf/dl-tunables.list: Add glibc.malloc.mxfast.

    * manual/tunables.texi: Document it.

    * malloc/malloc.c (do_set_mxfast): New.

    (__libc_mallopt): Call it.

    * malloc/arena.c: Add mxfast tunable.

    * malloc/tst-mxfast.c: New.

    * malloc/Makefile: Add it.

    Reviewed-by: Carlos O'Donell <carlos@redhat.com>

    (cherry picked from commit c48d92b430c480de06762f80c104922239416826)

diff --git a/elf/dl-tunables.list b/elf/dl-tunables.list

index 1f8ecb8437a0460f..1ff6fcb6f24f93a8 100644

--- a/elf/dl-tunables.list

+++ b/elf/dl-tunables.list

@@ -85,6 +85,11 @@ glibc {

     tcache_unsorted_limit {

       type: SIZE_T

     }

+    mxfast {

+      type: SIZE_T

+      minval: 0

+      security_level: SXID_IGNORE

+    }

   }

   tune {

     hwcap_mask {

diff --git a/malloc/Makefile b/malloc/Makefile

index 228a1279a5960d8c..bf9a53cb7c5ebacb 100644

--- a/malloc/Makefile

+++ b/malloc/Makefile

@@ -39,6 +39,7 @@ tests := mallocbug tst-malloc tst-valloc tst-calloc tst-obstack \

 	 tst-malloc-too-large \

 	 tst-malloc-stats-cancellation \

 	 tst-tcfree1 tst-tcfree2 tst-tcfree3 \

+	 tst-mxfast \

 tests-static := \

 	 tst-interpose-static-nothread \

@@ -196,6 +197,8 @@ tst-malloc-usable-static-ENV = $(tst-malloc-usable-ENV)

 tst-malloc-usable-tunables-ENV = GLIBC_TUNABLES=glibc.malloc.check=3

 tst-malloc-usable-static-tunables-ENV = $(tst-malloc-usable-tunables-ENV)

+tst-mxfast-ENV = GLIBC_TUNABLES=glibc.malloc.tcache_count=0:glibc.malloc.mxfast=0

+

 ifeq ($(experimental-malloc),yes)

 CPPFLAGS-malloc.c += -DUSE_TCACHE=1

 else

diff --git a/malloc/arena.c b/malloc/arena.c

index ff8fd5d2a7e51ac8..f5c7ad4570ad6186 100644

--- a/malloc/arena.c

+++ b/malloc/arena.c

@@ -237,6 +237,7 @@ TUNABLE_CALLBACK_FNDECL (set_tcache_max, size_t)

 TUNABLE_CALLBACK_FNDECL (set_tcache_count, size_t)

 TUNABLE_CALLBACK_FNDECL (set_tcache_unsorted_limit, size_t)

 #endif

+TUNABLE_CALLBACK_FNDECL (set_mxfast, size_t)

 #else

 /* Initialization routine. */

 #include <string.h>

@@ -324,6 +325,7 @@ ptmalloc_init (void)

   TUNABLE_GET (tcache_unsorted_limit, size_t,

 	       TUNABLE_CALLBACK (set_tcache_unsorted_limit));

 # endif

+  TUNABLE_GET (mxfast, size_t, TUNABLE_CALLBACK (set_mxfast));

 #else

   const char *s = NULL;

   if (__glibc_likely (_environ != NULL))

diff --git a/malloc/malloc.c b/malloc/malloc.c

index fcf480acdaea1b86..9756ed0a0d28c5f6 100644

--- a/malloc/malloc.c

+++ b/malloc/malloc.c

@@ -5142,6 +5142,19 @@ do_set_tcache_unsorted_limit (size_t value)

 }

 #endif

+static inline int

+__always_inline

+do_set_mxfast (size_t value)

+{

+  if (value >= 0 && value <= MAX_FAST_SIZE)

+    {

+      LIBC_PROBE (memory_mallopt_mxfast, 2, value, get_max_fast ());

+      set_max_fast (value);

+      return 1;

+    }

+  return 0;

+}

+

 int

 __libc_mallopt (int param_number, int value)

 {

@@ -5161,13 +5174,7 @@ __libc_mallopt (int param_number, int value)

   switch (param_number)

     {

     case M_MXFAST:

-      if (value >= 0 && value <= MAX_FAST_SIZE)

-        {

-          LIBC_PROBE (memory_mallopt_mxfast, 2, value, get_max_fast ());

-          set_max_fast (value);

-        }

-      else

-        res = 0;

+      do_set_mxfast (value);

       break;

     case M_TRIM_THRESHOLD:

diff --git a/malloc/tst-mxfast.c b/malloc/tst-mxfast.c

new file mode 100644

index 0000000000000000..7a371d2f9d2f0005

--- /dev/null

+++ b/malloc/tst-mxfast.c

@@ -0,0 +1,50 @@

+/* Test that glibc.malloc.mxfast tunable works.

+   Copyright (C) 2018, 2019 Free Software Foundation, Inc.

+   This file is part of the GNU C Library.

+

+   The GNU C Library is free software; you can redistribute it and/or

+   modify it under the terms of the GNU Lesser General Public

+   License as published by the Free Software Foundation; either

+   version 2.1 of the License, or (at your option) any later version.

+

+   The GNU C Library is distributed in the hope that it will be useful,

+   but WITHOUT ANY WARRANTY; without even the implied warranty of

+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU

+   Lesser General Public License for more details.

+

+   You should have received a copy of the GNU Lesser General Public

+   License along with the GNU C Library; if not, see

+   <http://www.gnu.org/licenses/>.  */

+

+/* This test verifies that setting the glibc.malloc.mxfast tunable to

+   zero results in free'd blocks being returned to the small bins, not

+   the fast bins.  */

+

+#include <malloc.h>

+#include <assert.h>

+

+int

+do_test(void)

+{

+  struct mallinfo m;

+  char * volatile p1;

+  char * volatile p2;

+

+  /* Arbitrary value; must be in default fastbin range.  */

+  p1 = malloc (3);

+  /* Something large so that p1 isn't a "top block" */

+  p2 = malloc (512);

+  free (p1);

+

+  m = mallinfo();

+

+  /* This will fail if there are any blocks in the fastbins.  */

+  assert (m.smblks == 0);

+

+  /* To keep gcc happy.  */

+  free (p2);

+

+  return 0;

+}

+

+#include <support/test-driver.c>

diff --git a/manual/tunables.texi b/manual/tunables.texi

index f6c49250e3889ddd..3dc6f9a44592c030 100644

--- a/manual/tunables.texi

+++ b/manual/tunables.texi

@@ -213,6 +213,18 @@ pre-fill the per-thread cache with.  The default, or when set to zero,

 is no limit.

 @end deftp

+@deftp Tunable glibc.malloc.mxfast

+One of the optimizations malloc uses is to maintain a series of ``fast

+bins'' that hold chunks up to a specific size.  The default and

+maximum size which may be held this way is 80 bytes on 32-bit systems

+or 160 bytes on 64-bit systems.  Applications which value size over

+speed may choose to reduce the size of requests which are serviced

+from fast bins with this tunable.  Note that the value specified

+includes malloc's internal overhead, which is normally the size of one

+pointer, so add 4 on 32-bit systems or 8 on 64-bit systems to the size

+passed to @code{malloc} for the largest bin size to enable.

+@end deftp

+

 @node Elision Tunables

 @section Elision Tunables

 @cindex elision tunables