From: Pavel Begunkov <asml.silence@gmail.com>
To: Alexander Viro <viro@zeniv.linux.org.uk>,
willy@infradead.org, linux-fsdevel@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: [PATCH v2] fs: optimise kiocb_set_rw_flags()
Date: Fri, 17 Jan 2020 04:32:37 +0300 [thread overview]
Message-ID: <5328b35d948ea2a3aa5df2b1d740c7cb1f38c846.1579224594.git.asml.silence@gmail.com> (raw)
In-Reply-To: <8cecd243-38aa-292d-15cd-49b485f9253f@gmail.com>
kiocb_set_rw_flags() generates a poor code with several memory writes
and a lot of jumps. Help compilers to optimise it.
Tested with gcc 9.2 on x64-86, and as a result, it its output now is a
plain code without jumps accumulating in a register before a memory
write.
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
---
v2: check for 0 flags in advance (Matthew Wilcox)
include/linux/fs.h | 16 +++++++++++-----
1 file changed, 11 insertions(+), 5 deletions(-)
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 98e0349adb52..22b46fc8fdfa 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -3402,22 +3402,28 @@ static inline int iocb_flags(struct file *file)
static inline int kiocb_set_rw_flags(struct kiocb *ki, rwf_t flags)
{
+ int kiocb_flags = 0;
+
+ if (!flags)
+ return 0;
if (unlikely(flags & ~RWF_SUPPORTED))
return -EOPNOTSUPP;
if (flags & RWF_NOWAIT) {
if (!(ki->ki_filp->f_mode & FMODE_NOWAIT))
return -EOPNOTSUPP;
- ki->ki_flags |= IOCB_NOWAIT;
+ kiocb_flags |= IOCB_NOWAIT;
}
if (flags & RWF_HIPRI)
- ki->ki_flags |= IOCB_HIPRI;
+ kiocb_flags |= IOCB_HIPRI;
if (flags & RWF_DSYNC)
- ki->ki_flags |= IOCB_DSYNC;
+ kiocb_flags |= IOCB_DSYNC;
if (flags & RWF_SYNC)
- ki->ki_flags |= (IOCB_DSYNC | IOCB_SYNC);
+ kiocb_flags |= (IOCB_DSYNC | IOCB_SYNC);
if (flags & RWF_APPEND)
- ki->ki_flags |= IOCB_APPEND;
+ kiocb_flags |= IOCB_APPEND;
+
+ ki->ki_flags |= kiocb_flags;
return 0;
}
--
2.24.0
next prev parent reply other threads:[~2020-01-17 1:33 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-17 1:16 [PATCH] fs: optimise kiocb_set_rw_flags() Pavel Begunkov
2020-01-17 1:21 ` Matthew Wilcox
2020-01-17 1:23 ` Pavel Begunkov
2020-01-17 1:32 ` Pavel Begunkov [this message]
2020-01-31 13:01 ` [PATCH v2] " Pavel Begunkov
2020-02-12 12:57 ` Pavel Begunkov
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