[PATCH 3/9] malloc: remove allocation from fastbin, and trim_fastbins

[DJ Delorie]

Dev Jain <dev.jain@arm.com> writes:

> -    TRIM_FASTBINS              0

Ok.  We disabled this feature anyway.

> -/*
> -  TRIM_FASTBINS controls whether free() of a very small chunk can
> -  immediately lead to trimming. Setting to true (1) can reduce memory
> -  footprint, but will almost always slow down programs that use a lot
> -  of small chunks.
> -
> -  Define this only if you are willing to give up some speed to more
> -  aggressively reduce system-level memory footprint when releasing
> -  memory in programs that use many small chunks.  You can get
> -  essentially the same effect by setting MXFAST to 0, but this can
> -  lead to even greater slowdowns in programs using many small chunks.
> -  TRIM_FASTBINS is an in-between compile-time option, that disables
> -  only those chunks bordering topmost memory from being placed in
> -  fastbins.
> -*/
> -
> -#ifndef TRIM_FASTBINS
> -#define TRIM_FASTBINS  0
> -#endif
> -

Ok.

> -  Trim settings interact with fastbin (MXFAST) settings: Unless
> -  TRIM_FASTBINS is defined, automatic trimming never takes place upon
> -  freeing a chunk with size less than or equal to MXFAST. Trimming is
> -  instead delayed until subsequent freeing of larger chunks. However,
> -  you can still force an attempted trim by calling malloc_trim.
> +  you can force an attempted trim by calling malloc_trim.

"you" needs to be capitalized in this case.

> -  /*
> -     If the size qualifies as a fastbin, first check corresponding bin.
> -     This code is safe to execute even if av is not yet initialized, so we
> -     can try it without checking, which saves some time on this fast path.
> -   */
> -
> -#define REMOVE_FB(fb, victim, pp)			\
> -  do							\
> -    {							\
> -      victim = pp;					\
> -      if (victim == NULL)				\
> -	break;						\
> -      pp = REVEAL_PTR (victim->fd);                                     \
> -      if (__glibc_unlikely (pp != NULL && misaligned_chunk (pp)))       \
> -	malloc_printerr ("malloc(): unaligned fastbin chunk detected"); \
> -    }							\
> -  while ((pp = atomic_compare_and_exchange_val_acq (fb, pp, victim)) \
> -	 != victim);					\

Ok.

> -  if ((unsigned long) (nb) <= (unsigned long) (get_max_fast ()))
> -    {
> -      idx = fastbin_index (nb);
> - . . .
> -    }
> -

Ok.

>  static void
>  _int_free_chunk (mstate av, mchunkptr p, INTERNAL_SIZE_T size, int have_lock)
>  {
> -  mfastbinptr *fb;             /* associated fastbin */
> -
> -  /*
> -    If eligible, place chunk on a fastbin so it can be found
> -    and used quickly in malloc.
> -  */
> -
> -  if ((unsigned long)(size) <= (unsigned long)(get_max_fast ())
> -
> - . . .
> -  }
> -

Ok.

>    /*
>      Consolidate other non-mmapped chunks as they arrive.
>    */
>  
> -  else if (!chunk_is_mmapped(p)) {
> +  if (!chunk_is_mmapped(p)) {

Ok.

LGTM other than the one capitalization fix.
Reviewed-by: DJ Delorie <dj@redhat.com>