From mboxrd@z Thu Jan 1 00:00:00 1970 From: James Simmons Date: Tue, 26 Feb 2019 20:55:49 +0000 (GMT) Subject: [lustre-devel] [PATCH 22/37] lustre: lprocfs: use log2.h macros instead of shift loop. In-Reply-To: <155053494599.24125.1795878344125234751.stgit@noble.brown> References: <155053473693.24125.6976971762921761309.stgit@noble.brown> <155053494599.24125.1795878344125234751.stgit@noble.brown> Message-ID: 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. Be aware rounddown_pow_of_two(n) is undefined when "n == 0". > 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); > } > > >