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: Re: [PATCH v2] fs: optimise kiocb_set_rw_flags()
Date: Wed, 12 Feb 2020 15:57:03 +0300 [thread overview]
Message-ID: <3fd1844b-d059-7729-8d09-ad51d11514fa@gmail.com> (raw)
In-Reply-To: <14929e52-9437-e856-7eff-4e5b45968f89@gmail.com>
On 1/31/2020 4:01 PM, Pavel Begunkov wrote:
> On 1/17/2020 4:32 AM, Pavel Begunkov wrote:
>> 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.
>
> Humble ping
Anyone?
>
>>
>> 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;
>> }
>>
>>
>
--
Pavel Begunkov
prev parent reply other threads:[~2020-02-12 12:57 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 ` [PATCH v2] " Pavel Begunkov
2020-01-31 13:01 ` Pavel Begunkov
2020-02-12 12:57 ` Pavel Begunkov [this message]
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