diff mbox series

malloc: Remove bin scanning from memalign (bug 30723)

Message ID 87pm3uajev.fsf@oldenburg.str.redhat.com
State New
Headers show
Series malloc: Remove bin scanning from memalign (bug 30723) | expand

Commit Message

Florian Weimer Aug. 10, 2023, 5:36 p.m. UTC 
On the test workload (mpv --cache=yes with VP9 video decoding), the
bin scanning has a very poor success rate (less than 2%).  The tcache
scanning has about 50% success rate, so keep that.

---
DJ, this is on top of my other patch.  Given that the chunk scanning
code has such a small hit rate on the workload, I have just removed it.

I think we need better data structures before we can bring this back,
otherwise most workloads with a high number of memalign calls suffer too
much.  Typical heaps have hundreds, if not thousands, of free list
entries.  I had not considered the impact of that on repeated memalign
calls.

What do you think?

Tested x86_64-linux-gnu.

Thanks,
Florian

 malloc/malloc.c | 127 +++-----------------------------------------------------
 1 file changed, 5 insertions(+), 122 deletions(-)


base-commit: e02ce52fd890d3b5197f78cf25096faa9446fa3d

Comments

Maxim Kuvyrkov Aug. 11, 2023, 8:54 a.m. UTC | #1 
Hi Florian,

This fails testing on aarch64-linux-gnu:

FAIL: malloc/tst-memalign-2-malloc-hugetlb1
original exit status 1
error: tst-memalign-2.c:155: not true: count > LN / 2
error: 1 test failures

FAIL: malloc/tst-memalign-2-malloc-hugetlb2
original exit status 1
error: tst-memalign-2.c:155: not true: count > LN / 2
error: 1 test failures

FAIL: malloc/tst-memalign-2
original exit status 1
error: tst-memalign-2.c:155: not true: count > LN / 2
error: 1 test failures

Let me know if you need any assistance in reproducing this.

Thanks!

--
Maxim Kuvyrkov
https://www.linaro.org




> On Aug 10, 2023, at 21:36, Florian Weimer via Libc-alpha <libc-alpha@sourceware.org> wrote:
> 
> On the test workload (mpv --cache=yes with VP9 video decoding), the
> bin scanning has a very poor success rate (less than 2%).  The tcache
> scanning has about 50% success rate, so keep that.
> 
> ---
> DJ, this is on top of my other patch.  Given that the chunk scanning
> code has such a small hit rate on the workload, I have just removed it.
> 
> I think we need better data structures before we can bring this back,
> otherwise most workloads with a high number of memalign calls suffer too
> much.  Typical heaps have hundreds, if not thousands, of free list
> entries.  I had not considered the impact of that on repeated memalign
> calls.
> 
> What do you think?
> 
> Tested x86_64-linux-gnu.
> 
> Thanks,
> Florian
> 
> malloc/malloc.c | 127 +++-----------------------------------------------------
> 1 file changed, 5 insertions(+), 122 deletions(-)
> 
> diff --git a/malloc/malloc.c b/malloc/malloc.c
> index 948f9759af..9c2cab7a59 100644
> --- a/malloc/malloc.c
> +++ b/malloc/malloc.c
> @@ -5082,7 +5082,6 @@ _int_memalign (mstate av, size_t alignment, size_t bytes)
>   mchunkptr remainder;            /* spare room at end to split off */
>   unsigned long remainder_size;   /* its size */
>   INTERNAL_SIZE_T size;
> -  mchunkptr victim;
> 
>   nb = checked_request2size (bytes);
>   if (nb == 0)
> @@ -5101,129 +5100,13 @@ _int_memalign (mstate av, size_t alignment, size_t bytes)
>      we don't find anything in those bins, the common malloc code will
>      scan starting at 2x.  */
> 
> -  /* This will be set if we found a candidate chunk.  */
> -  victim = NULL;
> +  /* Call malloc with worst case padding to hit alignment. */
> +  m = (char *) (_int_malloc (av, nb + alignment + MINSIZE));
> 
> -  /* Fast bins are singly-linked, hard to remove a chunk from the middle
> -     and unlikely to meet our alignment requirements.  We have not done
> -     any experimentation with searching for aligned fastbins.  */
> +  if (m == 0)
> +    return 0;           /* propagate failure */
> 
> -  if (av != NULL)
> -    {
> -      int first_bin_index;
> -      int first_largebin_index;
> -      int last_bin_index;
> -
> -      if (in_smallbin_range (nb))
> - first_bin_index = smallbin_index (nb);
> -      else
> - first_bin_index = largebin_index (nb);
> -
> -      if (in_smallbin_range (nb * 2))
> - last_bin_index = smallbin_index (nb * 2);
> -      else
> - last_bin_index = largebin_index (nb * 2);
> -
> -      first_largebin_index = largebin_index (MIN_LARGE_SIZE);
> -
> -      int victim_index;                 /* its bin index */
> -
> -      for (victim_index = first_bin_index;
> -   victim_index < last_bin_index;
> -   victim_index ++)
> - {
> -  victim = NULL;
> -
> -  if (victim_index < first_largebin_index)
> -    {
> -      /* Check small bins.  Small bin chunks are doubly-linked despite
> - being the same size.  */
> -
> -      mchunkptr fwd;                    /* misc temp for linking */
> -      mchunkptr bck;                    /* misc temp for linking */
> -
> -      bck = bin_at (av, victim_index);
> -      fwd = bck->fd;
> -      while (fwd != bck)
> - {
> -  if (chunk_ok_for_memalign (fwd, alignment, nb) > 0)
> -    {
> -      victim = fwd;
> -
> -      /* Unlink it */
> -      victim->fd->bk = victim->bk;
> -      victim->bk->fd = victim->fd;
> -      break;
> -    }
> -
> -  fwd = fwd->fd;
> - }
> -    }
> -  else
> -    {
> -      /* Check large bins.  */
> -      mchunkptr fwd;                    /* misc temp for linking */
> -      mchunkptr bck;                    /* misc temp for linking */
> -      mchunkptr best = NULL;
> -      size_t best_size = 0;
> -
> -      bck = bin_at (av, victim_index);
> -      fwd = bck->fd;
> -
> -      while (fwd != bck)
> - {
> -  int extra;
> -
> -  if (chunksize (fwd) < nb)
> -    break;
> -  extra = chunk_ok_for_memalign (fwd, alignment, nb);
> -  if (extra > 0
> -      && (extra <= best_size || best == NULL))
> -    {
> -      best = fwd;
> -      best_size = extra;
> -    }
> -
> -  fwd = fwd->fd;
> - }
> -      victim = best;
> -
> -      if (victim != NULL)
> - {
> -  unlink_chunk (av, victim);
> -  break;
> - }
> -    }
> -
> -  if (victim != NULL)
> -    break;
> - }
> -    }
> -
> -  /* Strategy: find a spot within that chunk that meets the alignment
> -     request, and then possibly free the leading and trailing space.
> -     This strategy is incredibly costly and can lead to external
> -     fragmentation if header and footer chunks are unused.  */
> -
> -  if (victim != NULL)
> -    {
> -      p = victim;
> -      m = chunk2mem (p);
> -      set_inuse (p);
> -      if (av != &main_arena)
> - set_non_main_arena (p);
> -    }
> -  else
> -    {
> -      /* Call malloc with worst case padding to hit alignment. */
> -
> -      m = (char *) (_int_malloc (av, nb + alignment + MINSIZE));
> -
> -      if (m == 0)
> - return 0;           /* propagate failure */
> -
> -      p = mem2chunk (m);
> -    }
> +  p = mem2chunk (m);
> 
>   if ((((unsigned long) (m)) % alignment) != 0)   /* misaligned */
>     {
> 
> base-commit: e02ce52fd890d3b5197f78cf25096faa9446fa3d
>
Florian Weimer Aug. 11, 2023, 9:14 a.m. UTC | #2 
* Maxim Kuvyrkov:

> Hi Florian,
>
> This fails testing on aarch64-linux-gnu:
>
> FAIL: malloc/tst-memalign-2-malloc-hugetlb1
> original exit status 1
> error: tst-memalign-2.c:155: not true: count > LN / 2
> error: 1 test failures
>
> FAIL: malloc/tst-memalign-2-malloc-hugetlb2
> original exit status 1
> error: tst-memalign-2.c:155: not true: count > LN / 2
> error: 1 test failures
>
> FAIL: malloc/tst-memalign-2
> original exit status 1
> error: tst-memalign-2.c:155: not true: count > LN / 2
> error: 1 test failures
>
> Let me know if you need any assistance in reproducing this.

I can't reproduce this on x86-64, but looking at this particular
subtest, I agree that it should fail after the removal of the bin
scanning code. 8-/

I'll send a v2.

Thanks,
Florian
Florian Weimer Aug. 11, 2023, 2:52 p.m. UTC | #3 
* Florian Weimer:

> * Maxim Kuvyrkov:
>
>> Hi Florian,
>>
>> This fails testing on aarch64-linux-gnu:
>>
>> FAIL: malloc/tst-memalign-2-malloc-hugetlb1
>> original exit status 1
>> error: tst-memalign-2.c:155: not true: count > LN / 2
>> error: 1 test failures
>>
>> FAIL: malloc/tst-memalign-2-malloc-hugetlb2
>> original exit status 1
>> error: tst-memalign-2.c:155: not true: count > LN / 2
>> error: 1 test failures
>>
>> FAIL: malloc/tst-memalign-2
>> original exit status 1
>> error: tst-memalign-2.c:155: not true: count > LN / 2
>> error: 1 test failures
>>
>> Let me know if you need any assistance in reproducing this.
>
> I can't reproduce this on x86-64, but looking at this particular
> subtest, I agree that it should fail after the removal of the bin
> scanning code. 8-/
>
> I'll send a v2.

And I'll need a v3.  The test is still valid with the
return-to-lowest-allocator patches in memalign, and passes.  But this
commit here applies separately without the conflict, and then the test
fails (as expected).

Thanks,
Florian
Andreas Schwab Aug. 12, 2023, 6:52 a.m. UTC | #4 
malloc.c: In function '_int_free':
malloc.c:4496:13: error: unused variable 'fwd' [-Werror=unused-variable]
 4496 |   mchunkptr fwd;               /* misc temp for linking */
      |             ^~~
malloc.c:4495:13: error: unused variable 'bck' [-Werror=unused-variable]
 4495 |   mchunkptr bck;               /* misc temp for linking */
      |             ^~~
malloc.c:4494:19: error: unused variable 'prevsize' [-Werror=unused-variable]
 4494 |   INTERNAL_SIZE_T prevsize;    /* size of previous contiguous chunk */
      |                   ^~~~~~~~
malloc.c:4493:7: error: unused variable 'nextinuse' [-Werror=unused-variable]
 4493 |   int nextinuse;               /* true if nextchunk is used */
      |       ^~~~~~~~~
malloc.c:4492:19: error: unused variable 'nextsize' [-Werror=unused-variable]
 4492 |   INTERNAL_SIZE_T nextsize;    /* its size */
      |                   ^~~~~~~~
malloc.c:4491:13: error: unused variable 'nextchunk' [-Werror=unused-variable]
 4491 |   mchunkptr nextchunk;         /* next contiguous chunk */
      |             ^~~~~~~~~
cc1: all warnings being treated as errors
make[2]: *** [../o-iterator.mk:9: /home/abuild/rpmbuild/BUILD/glibc-2.38.9000.31.g084fb31bc2/cc-base/malloc/malloc.o] Error 1
Florian Weimer Aug. 12, 2023, 1:23 p.m. UTC | #5 
* Andreas Schwab:

> malloc.c: In function '_int_free':
> malloc.c:4496:13: error: unused variable 'fwd' [-Werror=unused-variable]
>  4496 |   mchunkptr fwd;               /* misc temp for linking */
>       |             ^~~
> malloc.c:4495:13: error: unused variable 'bck' [-Werror=unused-variable]
>  4495 |   mchunkptr bck;               /* misc temp for linking */
>       |             ^~~
> malloc.c:4494:19: error: unused variable 'prevsize' [-Werror=unused-variable]
>  4494 |   INTERNAL_SIZE_T prevsize;    /* size of previous contiguous chunk */
>       |                   ^~~~~~~~
> malloc.c:4493:7: error: unused variable 'nextinuse' [-Werror=unused-variable]
>  4493 |   int nextinuse;               /* true if nextchunk is used */
>       |       ^~~~~~~~~
> malloc.c:4492:19: error: unused variable 'nextsize' [-Werror=unused-variable]
>  4492 |   INTERNAL_SIZE_T nextsize;    /* its size */
>       |                   ^~~~~~~~
> malloc.c:4491:13: error: unused variable 'nextchunk' [-Werror=unused-variable]
>  4491 |   mchunkptr nextchunk;         /* next contiguous chunk */
>       |             ^~~~~~~~~
> cc1: all warnings being treated as errors
> make[2]: *** [../o-iterator.mk:9: /home/abuild/rpmbuild/BUILD/glibc-2.38.9000.31.g084fb31bc2/cc-base/malloc/malloc.o] Error 1

This is a disable-tcache configuration, right? Will fix.
Florian Weimer Aug. 12, 2023, 1:33 p.m. UTC | #6 
* Florian Weimer:

> * Andreas Schwab:
>
>> malloc.c: In function '_int_free':
>> malloc.c:4496:13: error: unused variable 'fwd' [-Werror=unused-variable]
>>  4496 |   mchunkptr fwd;               /* misc temp for linking */
>>       |             ^~~
>> malloc.c:4495:13: error: unused variable 'bck' [-Werror=unused-variable]
>>  4495 |   mchunkptr bck;               /* misc temp for linking */
>>       |             ^~~
>> malloc.c:4494:19: error: unused variable 'prevsize' [-Werror=unused-variable]
>>  4494 |   INTERNAL_SIZE_T prevsize;    /* size of previous contiguous chunk */
>>       |                   ^~~~~~~~
>> malloc.c:4493:7: error: unused variable 'nextinuse' [-Werror=unused-variable]
>>  4493 |   int nextinuse;               /* true if nextchunk is used */
>>       |       ^~~~~~~~~
>> malloc.c:4492:19: error: unused variable 'nextsize' [-Werror=unused-variable]
>>  4492 |   INTERNAL_SIZE_T nextsize;    /* its size */
>>       |                   ^~~~~~~~
>> malloc.c:4491:13: error: unused variable 'nextchunk' [-Werror=unused-variable]
>>  4491 |   mchunkptr nextchunk;         /* next contiguous chunk */
>>       |             ^~~~~~~~~
>> cc1: all warnings being treated as errors
>> make[2]: *** [../o-iterator.mk:9: /home/abuild/rpmbuild/BUILD/glibc-2.38.9000.31.g084fb31bc2/cc-base/malloc/malloc.o] Error 1
>
> This is a disable-tcache configuration, right? Will fix.

No, the variables are always unused.  This looks like a GCC bug on my
side.  It's strange that it appears with GCC 12 and GCC 13.  Which
version do you use?
Andreas Schwab Aug. 12, 2023, 2:50 p.m. UTC | #7 
This is openSUSE Tumbleweed, which uses gcc 13.

https://build.opensuse.org/package/show/home:Andreas_Schwab:glibc/glibc
Xi Ruoyao Aug. 14, 2023, 2:14 a.m. UTC | #8 
On Sat, 2023-08-12 at 15:33 +0200, Florian Weimer wrote:
> * Florian Weimer:
> 
> > * Andreas Schwab:
> > 
> > > malloc.c: In function '_int_free':
> > > malloc.c:4496:13: error: unused variable 'fwd' [-Werror=unused-variable]
> > >   4496 |   mchunkptr fwd;               /* misc temp for linking */
> > >        |             ^~~
> > > malloc.c:4495:13: error: unused variable 'bck' [-Werror=unused-variable]
> > >   4495 |   mchunkptr bck;               /* misc temp for linking */
> > >        |             ^~~
> > > malloc.c:4494:19: error: unused variable 'prevsize' [-Werror=unused-variable]
> > >   4494 |   INTERNAL_SIZE_T prevsize;    /* size of previous contiguous chunk */
> > >        |                   ^~~~~~~~
> > > malloc.c:4493:7: error: unused variable 'nextinuse' [-Werror=unused-variable]
> > >   4493 |   int nextinuse;               /* true if nextchunk is used */
> > >        |       ^~~~~~~~~
> > > malloc.c:4492:19: error: unused variable 'nextsize' [-Werror=unused-variable]
> > >   4492 |   INTERNAL_SIZE_T nextsize;    /* its size */
> > >        |                   ^~~~~~~~
> > > malloc.c:4491:13: error: unused variable 'nextchunk' [-Werror=unused-variable]
> > >   4491 |   mchunkptr nextchunk;         /* next contiguous chunk */
> > >        |             ^~~~~~~~~
> > > cc1: all warnings being treated as errors
> > > make[2]: *** [../o-iterator.mk:9: /home/abuild/rpmbuild/BUILD/glibc-2.38.9000.31.g084fb31bc2/cc-base/malloc/malloc.o] Error 1
> > 
> > This is a disable-tcache configuration, right? Will fix.
> 
> No, the variables are always unused.  This looks like a GCC bug on my
> side.  It's strange that it appears with GCC 12 and GCC 13.  Which
> version do you use?

But I just removed these variables in a patched (applying
542b1105852568c3ebc712225ae78b8c8ba31a78 and v3 of this) Glibc-2.38 and
it builds OK.  So I can bet they are really unused...
Florian Weimer Aug. 14, 2023, 9:16 a.m. UTC | #9 
* Andreas Schwab:

> malloc.c: In function '_int_free':
> malloc.c:4496:13: error: unused variable 'fwd' [-Werror=unused-variable]
>  4496 |   mchunkptr fwd;               /* misc temp for linking */
>       |             ^~~
> malloc.c:4495:13: error: unused variable 'bck' [-Werror=unused-variable]
>  4495 |   mchunkptr bck;               /* misc temp for linking */
>       |             ^~~
> malloc.c:4494:19: error: unused variable 'prevsize' [-Werror=unused-variable]
>  4494 |   INTERNAL_SIZE_T prevsize;    /* size of previous contiguous chunk */
>       |                   ^~~~~~~~
> malloc.c:4493:7: error: unused variable 'nextinuse' [-Werror=unused-variable]
>  4493 |   int nextinuse;               /* true if nextchunk is used */
>       |       ^~~~~~~~~
> malloc.c:4492:19: error: unused variable 'nextsize' [-Werror=unused-variable]
>  4492 |   INTERNAL_SIZE_T nextsize;    /* its size */
>       |                   ^~~~~~~~
> malloc.c:4491:13: error: unused variable 'nextchunk' [-Werror=unused-variable]
>  4491 |   mchunkptr nextchunk;         /* next contiguous chunk */
>       |             ^~~~~~~~~
> cc1: all warnings being treated as errors
> make[2]: *** [../o-iterator.mk:9: /home/abuild/rpmbuild/BUILD/glibc-2.38.9000.31.g084fb31bc2/cc-base/malloc/malloc.o] Error 1

Found it, I believe I'm not seeing this because of:

commit 78ceef25d64efeeb6067d1cb282a00466e637e2a
Author: Adhemerval Zanella Netto <adhemerval.zanella@linaro.org>
Date:   Mon Jul 24 14:22:27 2023 -0300

    configure: Remove --enable-all-warnings option
    
    The option is not activelly tested and has bitrotten, to fix it
    would require a lot of work and multiple fixes.  A better option
    would to evaluate each option and enable the warning if it makes
    sense.
    Reviewed-by: Siddhesh Poyarekar <siddhesh@sourceware.org>

diff --git a/Makeconfig b/Makeconfig
index 77d7fd14df..c4dd9ea8f2 100644
--- a/Makeconfig
+++ b/Makeconfig
@@ -857,12 +857,7 @@ host-test-program-cmd = $(host-built-program-cmd)
 endif
 
 # Extra flags to pass to GCC.
-ifeq ($(all-warnings),yes)
-+gccwarn := -Wall -Wwrite-strings -Wcast-qual -Wbad-function-cast -Wmissing-noreturn -Wmissing-prototypes -Wmissing-declarations -Wcomment -Wcomments -Wtrigraphs -Wsign-compare -Wfloat-equal -Wmultichar
-else
-+gccwarn := -Wall -Wwrite-strings
-endif
-+gccwarn += -Wundef
+gccwarn := -Wall -Wwrite-strings -Wundef
 ifeq ($(enable-werror),yes)
 +gccwarn += -Werror
 endif

It dropped -Wall from glibc's default CFLAGS due to a typo (gccwarn
instead of +gccwarn).

Will test a fix with build-many-glibcs.py.

Thanks,
Florian
Adhemerval Zanella Aug. 15, 2023, 11:58 a.m. UTC | #10 
On 14/08/23 06:16, Florian Weimer wrote:
> * Andreas Schwab:
> 
>> malloc.c: In function '_int_free':
>> malloc.c:4496:13: error: unused variable 'fwd' [-Werror=unused-variable]
>>  4496 |   mchunkptr fwd;               /* misc temp for linking */
>>       |             ^~~
>> malloc.c:4495:13: error: unused variable 'bck' [-Werror=unused-variable]
>>  4495 |   mchunkptr bck;               /* misc temp for linking */
>>       |             ^~~
>> malloc.c:4494:19: error: unused variable 'prevsize' [-Werror=unused-variable]
>>  4494 |   INTERNAL_SIZE_T prevsize;    /* size of previous contiguous chunk */
>>       |                   ^~~~~~~~
>> malloc.c:4493:7: error: unused variable 'nextinuse' [-Werror=unused-variable]
>>  4493 |   int nextinuse;               /* true if nextchunk is used */
>>       |       ^~~~~~~~~
>> malloc.c:4492:19: error: unused variable 'nextsize' [-Werror=unused-variable]
>>  4492 |   INTERNAL_SIZE_T nextsize;    /* its size */
>>       |                   ^~~~~~~~
>> malloc.c:4491:13: error: unused variable 'nextchunk' [-Werror=unused-variable]
>>  4491 |   mchunkptr nextchunk;         /* next contiguous chunk */
>>       |             ^~~~~~~~~
>> cc1: all warnings being treated as errors
>> make[2]: *** [../o-iterator.mk:9: /home/abuild/rpmbuild/BUILD/glibc-2.38.9000.31.g084fb31bc2/cc-base/malloc/malloc.o] Error 1
> 
> Found it, I believe I'm not seeing this because of:
> 
> commit 78ceef25d64efeeb6067d1cb282a00466e637e2a
> Author: Adhemerval Zanella Netto <adhemerval.zanella@linaro.org>
> Date:   Mon Jul 24 14:22:27 2023 -0300
> 
>     configure: Remove --enable-all-warnings option
>     
>     The option is not activelly tested and has bitrotten, to fix it
>     would require a lot of work and multiple fixes.  A better option
>     would to evaluate each option and enable the warning if it makes
>     sense.
>     Reviewed-by: Siddhesh Poyarekar <siddhesh@sourceware.org>
> 
> diff --git a/Makeconfig b/Makeconfig
> index 77d7fd14df..c4dd9ea8f2 100644
> --- a/Makeconfig
> +++ b/Makeconfig
> @@ -857,12 +857,7 @@ host-test-program-cmd = $(host-built-program-cmd)
>  endif
>  
>  # Extra flags to pass to GCC.
> -ifeq ($(all-warnings),yes)
> -+gccwarn := -Wall -Wwrite-strings -Wcast-qual -Wbad-function-cast -Wmissing-noreturn -Wmissing-prototypes -Wmissing-declarations -Wcomment -Wcomments -Wtrigraphs -Wsign-compare -Wfloat-equal -Wmultichar
> -else
> -+gccwarn := -Wall -Wwrite-strings
> -endif
> -+gccwarn += -Wundef
> +gccwarn := -Wall -Wwrite-strings -Wundef
>  ifeq ($(enable-werror),yes)
>  +gccwarn += -Werror
>  endif
> 
> It dropped -Wall from glibc's default CFLAGS due to a typo (gccwarn
> instead of +gccwarn).
> 
> Will test a fix with build-many-glibcs.py.

Oops, sorry about that and thanks for fixing this up.
diff mbox series

Patch

diff --git a/malloc/malloc.c b/malloc/malloc.c
index 948f9759af..9c2cab7a59 100644
--- a/malloc/malloc.c
+++ b/malloc/malloc.c
@@ -5082,7 +5082,6 @@  _int_memalign (mstate av, size_t alignment, size_t bytes)
   mchunkptr remainder;            /* spare room at end to split off */
   unsigned long remainder_size;   /* its size */
   INTERNAL_SIZE_T size;
-  mchunkptr victim;
 
   nb = checked_request2size (bytes);
   if (nb == 0)
@@ -5101,129 +5100,13 @@  _int_memalign (mstate av, size_t alignment, size_t bytes)
      we don't find anything in those bins, the common malloc code will
      scan starting at 2x.  */
 
-  /* This will be set if we found a candidate chunk.  */
-  victim = NULL;
+  /* Call malloc with worst case padding to hit alignment. */
+  m = (char *) (_int_malloc (av, nb + alignment + MINSIZE));
 
-  /* Fast bins are singly-linked, hard to remove a chunk from the middle
-     and unlikely to meet our alignment requirements.  We have not done
-     any experimentation with searching for aligned fastbins.  */
+  if (m == 0)
+    return 0;           /* propagate failure */
 
-  if (av != NULL)
-    {
-      int first_bin_index;
-      int first_largebin_index;
-      int last_bin_index;
-
-      if (in_smallbin_range (nb))
-	first_bin_index = smallbin_index (nb);
-      else
-	first_bin_index = largebin_index (nb);
-
-      if (in_smallbin_range (nb * 2))
-	last_bin_index = smallbin_index (nb * 2);
-      else
-	last_bin_index = largebin_index (nb * 2);
-
-      first_largebin_index = largebin_index (MIN_LARGE_SIZE);
-
-      int victim_index;                 /* its bin index */
-
-      for (victim_index = first_bin_index;
-	   victim_index < last_bin_index;
-	   victim_index ++)
-	{
-	  victim = NULL;
-
-	  if (victim_index < first_largebin_index)
-	    {
-	      /* Check small bins.  Small bin chunks are doubly-linked despite
-		 being the same size.  */
-
-	      mchunkptr fwd;                    /* misc temp for linking */
-	      mchunkptr bck;                    /* misc temp for linking */
-
-	      bck = bin_at (av, victim_index);
-	      fwd = bck->fd;
-	      while (fwd != bck)
-		{
-		  if (chunk_ok_for_memalign (fwd, alignment, nb) > 0)
-		    {
-		      victim = fwd;
-
-		      /* Unlink it */
-		      victim->fd->bk = victim->bk;
-		      victim->bk->fd = victim->fd;
-		      break;
-		    }
-
-		  fwd = fwd->fd;
-		}
-	    }
-	  else
-	    {
-	      /* Check large bins.  */
-	      mchunkptr fwd;                    /* misc temp for linking */
-	      mchunkptr bck;                    /* misc temp for linking */
-	      mchunkptr best = NULL;
-	      size_t best_size = 0;
-
-	      bck = bin_at (av, victim_index);
-	      fwd = bck->fd;
-
-	      while (fwd != bck)
-		{
-		  int extra;
-
-		  if (chunksize (fwd) < nb)
-		    break;
-		  extra = chunk_ok_for_memalign (fwd, alignment, nb);
-		  if (extra > 0
-		      && (extra <= best_size || best == NULL))
-		    {
-		      best = fwd;
-		      best_size = extra;
-		    }
-
-		  fwd = fwd->fd;
-		}
-	      victim = best;
-
-	      if (victim != NULL)
-		{
-		  unlink_chunk (av, victim);
-		  break;
-		}
-	    }
-
-	  if (victim != NULL)
-	    break;
-	}
-    }
-
-  /* Strategy: find a spot within that chunk that meets the alignment
-     request, and then possibly free the leading and trailing space.
-     This strategy is incredibly costly and can lead to external
-     fragmentation if header and footer chunks are unused.  */
-
-  if (victim != NULL)
-    {
-      p = victim;
-      m = chunk2mem (p);
-      set_inuse (p);
-      if (av != &main_arena)
-	set_non_main_arena (p);
-    }
-  else
-    {
-      /* Call malloc with worst case padding to hit alignment. */
-
-      m = (char *) (_int_malloc (av, nb + alignment + MINSIZE));
-
-      if (m == 0)
-	return 0;           /* propagate failure */
-
-      p = mem2chunk (m);
-    }
+  p = mem2chunk (m);
 
   if ((((unsigned long) (m)) % alignment) != 0)   /* misaligned */
     {