Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754887AbbBBMEd (ORCPT ); Mon, 2 Feb 2015 07:04:33 -0500 Received: from cmexedge1.emulex.com ([138.239.224.99]:9338 "EHLO CMEXEDGE1.ext.emulex.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753954AbbBBMEb convert rfc822-to-8bit (ORCPT ); Mon, 2 Feb 2015 07:04:31 -0500 From: Selvin Xavier To: Rasmus Villemoes , Roland Dreier , Sean Hefty , Hal Rosenstock CC: "linux-rdma@vger.kernel.org" , "linux-kernel@vger.kernel.org" Subject: RE: [PATCH 1/2] infiniband: Help gcc generate better code for ocrdma_srq_toggle_bit Thread-Topic: [PATCH 1/2] infiniband: Help gcc generate better code for ocrdma_srq_toggle_bit Thread-Index: AQHQMZpd7Bs1LnyVI0GStbUR4d3ZhpzdXWfQ Date: Mon, 2 Feb 2015 12:04:28 +0000 Message-ID: <36AE2E863FF33A4F9FBBE296E34DBC8F5A09725E@CMEXMB1.ad.emulex.com> References: <1421419196-4659-1-git-send-email-linux@rasmusvillemoes.dk> In-Reply-To: <1421419196-4659-1-git-send-email-linux@rasmusvillemoes.dk> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-originating-ip: [10.226.192.248] Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 8BIT MIME-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2434 Lines: 63 Acked-by: Selvin Xavier 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 > --- > 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-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/