From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752395AbbAPOkQ (ORCPT ); Fri, 16 Jan 2015 09:40:16 -0500 Received: from mail-lb0-f174.google.com ([209.85.217.174]:39392 "EHLO mail-lb0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751335AbbAPOkO (ORCPT ); Fri, 16 Jan 2015 09:40:14 -0500 From: Rasmus Villemoes 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 Date: Fri, 16 Jan 2015 15:39:55 +0100 Message-Id: <1421419196-4659-1-git-send-email-linux@rasmusvillemoes.dk> X-Mailer: git-send-email 2.1.3 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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