ping On Fri, Jan 16 2015, Rasmus Villemoes <li...@rasmusvillemoes.dk> wrote:
> gcc emits a surprising amount of code in order to flip a bit. One > would think that a single instruction is enough. > > $ scripts/bloat-o-meter /tmp/ocrdma_verbs.o > drivers/infiniband/hw/ocrdma/ocrdma_verbs.o > add/remove: 0/0 grow/shrink: 0/3 up/down: 0/-142 (-142) > function old new delta > ocrdma_post_srq_recv 498 460 -38 > ocrdma_poll_cq 2010 1962 -48 > ocrdma_discard_cqes 495 439 -56 > > All three calls of ocrdma_srq_toggle_bit happen within spinlocks, so > saving a few useless instructions might be worthwhile. > > Signed-off-by: Rasmus Villemoes <li...@rasmusvillemoes.dk> > --- > drivers/infiniband/hw/ocrdma/ocrdma_verbs.c | 5 +---- > 1 file changed, 1 insertion(+), 4 deletions(-) > > diff --git a/drivers/infiniband/hw/ocrdma/ocrdma_verbs.c > b/drivers/infiniband/hw/ocrdma/ocrdma_verbs.c > index fb8d8c4dfbb9..eff11e6c6183 100644 > --- a/drivers/infiniband/hw/ocrdma/ocrdma_verbs.c > +++ b/drivers/infiniband/hw/ocrdma/ocrdma_verbs.c > @@ -1484,10 +1484,7 @@ static void ocrdma_srq_toggle_bit(struct ocrdma_srq > *srq, int idx) > int i = idx / 32; > unsigned int mask = (1 << (idx % 32)); > > - if (srq->idx_bit_fields[i] & mask) > - srq->idx_bit_fields[i] &= ~mask; > - else > - srq->idx_bit_fields[i] |= mask; > + srq->idx_bit_fields[i] ^= mask; > } > > static int ocrdma_hwq_free_cnt(struct ocrdma_qp_hwq_info *q) -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
