The tst-mallocfork2 and tst-mallocfork3 create large number of
subprocesss, around 11k for former and 20k for latter, to check
for malloc async-signal-safeness on both fork and _Fork.  However
they do not really exercise allocation patterns different than
other tests fro malloc itself, and the spawned process just exit
without any extra computation.

The tst-malloc-tcache-leak is similar, but creates 100k threads
and already checks the resulting with mallinfo.

These tests are also very sensitive to system load (since they
estresss heavy the kernel resource allocation), and adding them
on THP tunable and mcheck tests increase the pressure even more.

For THP the fork tests do not add any more coverage than other
tests.  The mcheck is also not enable for tst-malloc-tcache-leak.

Checked on x86_64-linux-gnu.
Reviewed-by: Carlos O'Donell <carlos@redhat.com>

This patch adds the strict checking for power-of-two alignments
in aligned_alloc(), and updates the manual accordingly.

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

All the tst malloc variants need the thread linking flags.

So tst-memalign-3 builds on Hurd.

Based on these comments in malloc.c:

   size field is or'ed with NON_MAIN_ARENA if the chunk was obtained
   from a non-main arena.  This is only set immediately before handing
   the chunk to the user, if necessary.

   The NON_MAIN_ARENA flag is never set for unsorted chunks, so it
   does not have to be taken into account in size comparisons.

When we pull a chunk off the unsorted list (or any list) we need to
make sure that flag is set properly before returning the chunk.

Use the rounded-up size for chunk_ok_for_memalign()

Do not scan the arena for reusable chunks if there's no arena.

Account for chunk overhead when determining if a chunk is a reuse
candidate.

mcheck interferes with memalign, so skip mcheck variants of
memalign tests.

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

This patch adds a chunk scanning algorithm to the _int_memalign code
path that reduces heap fragmentation by reusing already aligned chunks
instead of always looking for chunks of larger sizes and splitting
them.  The tcache macros are extended to allow removing a chunk from
the middle of the list.

The goal is to fix the pathological use cases where heaps grow
continuously in workloads that are heavy users of memalign.

Note that tst-memalign-2 checks for tcache operation, which
malloc-check bypasses.

Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>

And make always supported.  The configure option was added on glibc 2.25
and some features require it (such as hwcap mask, huge pages support, and
lock elisition tuning).  It also simplifies the build permutations.

Changes from v1:
 * Remove glibc.rtld.dynamic_sort changes, it is orthogonal and needs
   more discussion.
 * Cleanup more code.
Reviewed-by: Siddhesh Poyarekar <siddhesh@sourceware.org>

It is the default since 2.26 and it has bitrotten over the years,
By using it multiple malloc tests fails:

  FAIL: malloc/tst-memalign-2
  FAIL: malloc/tst-memalign-2-malloc-hugetlb1
  FAIL: malloc/tst-memalign-2-malloc-hugetlb2
  FAIL: malloc/tst-memalign-2-mcheck
  FAIL: malloc/tst-mxfast-malloc-hugetlb1
  FAIL: malloc/tst-mxfast-malloc-hugetlb2
  FAIL: malloc/tst-tcfree2
  FAIL: malloc/tst-tcfree2-malloc-hugetlb1
  FAIL: malloc/tst-tcfree2-malloc-hugetlb2

Checked on x86_64-linux-gnu.

Reviewed-by: DJ Delorie <dj@redhat.com>