From mboxrd@z Thu Jan 1 00:00:00 1970 From: NeilBrown Date: Tue, 19 Feb 2019 11:09:06 +1100 Subject: [lustre-devel] [PATCH 22/37] lustre: lprocfs: use log2.h macros instead of shift loop. In-Reply-To: <155053473693.24125.6976971762921761309.stgit@noble.brown> References: <155053473693.24125.6976971762921761309.stgit@noble.brown> Message-ID: <155053494599.24125.1795878344125234751.stgit@noble.brown> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: lustre-devel@lists.lustre.org 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. 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 a179b0d6979e..637aaca96888 100644 --- a/drivers/staging/lustre/lustre/obdclass/lprocfs_status.c +++ b/drivers/staging/lustre/lustre/obdclass/lprocfs_status.c @@ -341,9 +341,7 @@ 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); return sprintf(buf, "%llu\n", result); } @@ -364,8 +362,7 @@ 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); return sprintf(buf, "%llu\n", result); } @@ -387,8 +384,7 @@ 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); return sprintf(buf, "%llu\n", result); }