Message ID | 1421419196-4659-1-git-send-email-linux@rasmusvillemoes.dk (mailing list archive) |
---|---|
State | Accepted, archived |
Headers | show |
ping 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) -- To unsubscribe from this list: send the line "unsubscribe linux-rdma" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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.
Acked-by: Selvin Xavier <selvin.xavier@emulex.com> Thanks! > -----Original Message----- > From: linux-rdma-owner@vger.kernel.org [mailto:linux-rdma- > owner@vger.kernel.org] On Behalf Of Rasmus Villemoes > Sent: Friday, January 16, 2015 8:10 PM > To: Roland Dreier; Sean Hefty; Hal Rosenstock > Cc: Rasmus Villemoes; linux-rdma@vger.kernel.org; linux- > kernel@vger.kernel.org > Subject: [PATCH 1/2] infiniband: Help gcc generate better code for > ocrdma_srq_toggle_bit > > 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) > -- > 2.1.3 > > -- > To unsubscribe from this list: send the line "unsubscribe linux-rdma" in the > body of a message to majordomo@vger.kernel.org More majordomo info at > http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe linux-rdma" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Thank you Yann Droneaud for forwarding this mail. We will add an entry for ocrdma driver in MAINTAINERS file. Thanks, Selvin Xavier > -----Original Message----- > From: Yann Droneaud [mailto:ydroneaud@opteya.com] > Sent: Saturday, January 31, 2015 4:38 PM > To: Rasmus Villemoes > Cc: Roland Dreier; Sean Hefty; Hal Rosenstock; linux-rdma@vger.kernel.org; > linux-kernel@vger.kernel.org; Devesh Sharma; Selvin Xavier; Mitesh Ahuja > Subject: Re: [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 > >
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)
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(-)