Messages in this thread | | | Subject | Re: [PATCH v3 4/4] mm, slab_common: Make the loop for initializing KMALLOC_DMA start from 1 | From | Vlastimil Babka <> | Date | Tue, 10 Sep 2019 12:26:14 +0200 |
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On 9/10/19 3:26 AM, Pengfei Li wrote: > KMALLOC_DMA will be initialized only if KMALLOC_NORMAL with > the same index exists. > > And kmalloc_caches[KMALLOC_NORMAL][0] is always NULL. > > Therefore, the loop that initializes KMALLOC_DMA should start > at 1 instead of 0, which will reduce 1 meaningless attempt.
IMHO the saving of one iteration isn't worth making the code more subtle. KMALLOC_SHIFT_LOW would be nice, but that would skip 1 + 2 which are special.
Since you're doing these cleanups, have you considered reordering kmalloc_info, size_index, kmalloc_index() etc so that sizes 96 and 192 are ordered naturally between 64, 128 and 256? That should remove various special casing such as in create_kmalloc_caches(). I can't guarantee it will be possible without breaking e.g. constant folding optimizations etc., but seems to me it should be feasible. (There are definitely more places to change than those I listed.)
> Signed-off-by: Pengfei Li <lpf.vector@gmail.com> > --- > mm/slab_common.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/mm/slab_common.c b/mm/slab_common.c > index af45b5278fdc..c81fc7dc2946 100644 > --- a/mm/slab_common.c > +++ b/mm/slab_common.c > @@ -1236,7 +1236,7 @@ void __init create_kmalloc_caches(slab_flags_t flags) > slab_state = UP; > > #ifdef CONFIG_ZONE_DMA > - for (i = 0; i <= KMALLOC_SHIFT_HIGH; i++) { > + for (i = 1; i <= KMALLOC_SHIFT_HIGH; i++) { > struct kmem_cache *s = kmalloc_caches[KMALLOC_NORMAL][i]; > > if (s) { >
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