Re: [PATCH v2 0/1] MR2622: ntdll: Use log-linear bucketing for free lists.

[Jinoh Kang (＠iamahuman)]

Jinoh Kang (@iamahuman) commented about dlls/ntdll/heap.c:
> -
> - 72,  80,  88,  96, 104, 112, 120, 128,
> -
> - ...
> - */
>
> +static unsigned long get_free_list_block( size_t size )
>  {
> - if (index < HEAP_NB_SMALL_FREE_LISTS) return HEAP_MIN_BLOCK_SIZE + index * BLOCK_ALIGN;
> - return free_list_sizes[index - HEAP_NB_SMALL_FREE_LISTS];
> - size_t bsize = size / BLOCK_ALIGN;
> - DWORD b;
> - unsigned long block, log, linear;
> -
> - if ( bsize > UINT_MAX )
> -
>    return NB_FREE_LISTS - 1;
> -
> - /* find the highest bit */
> - if ( !BitScanReverse( &b, bsize ) || b < FREE_LIST_LINEAR_BITS )

How about shifting `bsize` right by `FREE_LIST_LINEAR_BITS` before passing it to `BitScanReverse`?  That'll eliminate extra comparsion as well as subtraction in `b - FREE_LIST_LINEAR_BITS`.