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SubjectRe: [PATCH 1/2] infiniband: Help gcc generate better code for ocrdma_srq_toggle_bit
Hi,

Le samedi 31 janvier 2015 à 00:00 +0100, Rasmus Villemoes a écrit :
> ping
>

As you're fixing ocrdma driver, I think you might want to find people
@emulex.com to review your patches.

BTW, there's no MAINTAINERS entry for ocrdma driver ... which is a pity.

> On Fri, Jan 16 2015, Rasmus Villemoes <linux@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 <linux@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)
> --

Regards.

--
Yann Droneaud
OPTEYA





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