From mboxrd@z Thu Jan 1 00:00:00 1970 From: James Simmons Date: Sun, 21 Jul 2019 22:12:14 -0400 Subject: [lustre-devel] [PATCH 02/10] lustre: lprocfs: use log2.h macros instead of shift loop. In-Reply-To: <1563761542-3708-1-git-send-email-jsimmons@infradead.org> References: <1563761542-3708-1-git-send-email-jsimmons@infradead.org> Message-ID: <1563761542-3708-3-git-send-email-jsimmons@infradead.org> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: lustre-devel@lists.lustre.org From: NeilBrown These shift loops seem to be trying to avoid doing a multiplication. The 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 WC-bug-id: https://jira.whamcloud.com/browse/LU-4423 Reviewed-on: https://review.whamcloud.com/35274 Reviewed-by: Petros Koutoupis Reviewed-by: Shaun Tancheff Reviewed-by: Oleg Drokin Signed-off-by: James Simmons --- fs/lustre/obdclass/lprocfs_status.c | 10 +++------- 1 file changed, 3 insertions(+), 7 deletions(-) diff --git a/fs/lustre/obdclass/lprocfs_status.c b/fs/lustre/obdclass/lprocfs_status.c index c5f5807..2b4302e 100644 --- a/fs/lustre/obdclass/lprocfs_status.c +++ b/fs/lustre/obdclass/lprocfs_status.c @@ -373,9 +373,7 @@ 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); } @@ -396,8 +394,7 @@ 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); } @@ -419,8 +416,7 @@ 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); } -- 1.8.3.1