From patchwork Mon Mar 4 06:31:38 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: NeilBrown X-Patchwork-Id: 10837349 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 3787C1399 for ; Mon, 4 Mar 2019 06:34:28 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 1FCDC29D78 for ; Mon, 4 Mar 2019 06:34:28 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 10B37289BC; Mon, 4 Mar 2019 06:34:28 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.9 required=2.0 tests=BAYES_00,MAILING_LIST_MULTI, RCVD_IN_DNSWL_NONE autolearn=ham version=3.3.1 Received: from pdx1-mailman02.dreamhost.com (pdx1-mailman02.dreamhost.com [64.90.62.194]) (using TLSv1.2 with cipher DHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.wl.linuxfoundation.org (Postfix) with ESMTPS id BEEBC289BC for ; Mon, 4 Mar 2019 06:34:27 +0000 (UTC) Received: from pdx1-mailman02.dreamhost.com (localhost [IPv6:::1]) by pdx1-mailman02.dreamhost.com (Postfix) with ESMTP id 7C0A221FF30; Sun, 3 Mar 2019 22:34:27 -0800 (PST) X-Original-To: lustre-devel@lists.lustre.org Delivered-To: lustre-devel-lustre.org@pdx1-mailman02.dreamhost.com Received: from mx1.suse.de (mx2.suse.de [195.135.220.15]) by pdx1-mailman02.dreamhost.com (Postfix) with ESMTP id 22DD021FC89 for ; Sun, 3 Mar 2019 22:34:26 -0800 (PST) X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 36D2FAC9C; Mon, 4 Mar 2019 06:34:25 +0000 (UTC) From: NeilBrown To: Andreas Dilger , James Simmons , Oleg Drokin Date: Mon, 04 Mar 2019 17:31:38 +1100 Message-ID: <155168109844.31333.11945665543393290075.stgit@noble.brown> In-Reply-To: <155168107971.31333.14345309795939467246.stgit@noble.brown> References: <155168107971.31333.14345309795939467246.stgit@noble.brown> User-Agent: StGit/0.17.1-dirty MIME-Version: 1.0 Subject: [lustre-devel] [PATCH 10/28] lustre: lprocfs: use log2.h macros instead of shift loop. X-BeenThere: lustre-devel@lists.lustre.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: "For discussing Lustre software development." List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Lustre Development List Errors-To: lustre-devel-bounces@lists.lustre.org Sender: "lustre-devel" X-Virus-Scanned: ClamAV using ClamSMTP These shift loops seem to be trying to avoid doing a multiplication. We same effect can be achieved more transparently using rounddown_pow_of_two(). Even though there is a multiplication in the C code, the resulting machine code just does a single shift. As rounddown_pow_of_two() is not defined for 0, and as we cannot be positively use the blk_size is non-zero, use blk_size ?: 1. Signed-off-by: NeilBrown --- .../lustre/lustre/obdclass/lprocfs_status.c | 10 +++------- 1 file changed, 3 insertions(+), 7 deletions(-) diff --git a/drivers/staging/lustre/lustre/obdclass/lprocfs_status.c b/drivers/staging/lustre/lustre/obdclass/lprocfs_status.c index 29c6b5d7abec..2af9dada195e 100644 --- a/drivers/staging/lustre/lustre/obdclass/lprocfs_status.c +++ b/drivers/staging/lustre/lustre/obdclass/lprocfs_status.c @@ -374,9 +374,7 @@ static ssize_t kbytestotal_show(struct kobject *kobj, struct attribute *attr, u32 blk_size = osfs.os_bsize >> 10; u64 result = osfs.os_blocks; - while (blk_size >>= 1) - result <<= 1; - + result *= rounddown_pow_of_two(blk_size ?: 1); return sprintf(buf, "%llu\n", result); } @@ -397,8 +395,7 @@ static ssize_t kbytesfree_show(struct kobject *kobj, struct attribute *attr, u32 blk_size = osfs.os_bsize >> 10; u64 result = osfs.os_bfree; - while (blk_size >>= 1) - result <<= 1; + result *= rounddown_pow_of_two(blk_size ?: 1); return sprintf(buf, "%llu\n", result); } @@ -420,8 +417,7 @@ static ssize_t kbytesavail_show(struct kobject *kobj, struct attribute *attr, u32 blk_size = osfs.os_bsize >> 10; u64 result = osfs.os_bavail; - while (blk_size >>= 1) - result <<= 1; + result *= rounddown_pow_of_two(blk_size ?: 1); return sprintf(buf, "%llu\n", result); }