From owner-freebsd-current  Sun Sep 20 15:26:07 1998
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	Mon, 21 Sep 1998 08:25:16 +1000
Date: Mon, 21 Sep 1998 08:25:16 +1000
From: Bruce Evans <bde@zeta.org.au>
Message-Id: <199809202225.IAA14238@godzilla.zeta.org.au>
To: bde@zeta.org.au, tlambert@primenet.com
Subject: Re: pthreads and sync writes
Cc: freebsd-current@FreeBSD.ORG, mal@algonet.se
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>> >Btw, O_FSYNC isn't documented in open.2. Fsync()ing also seems to
>> >be sligtly faster, is this an illusion or is there a difference
>> >in the semantics?
>> 
>> O_FSYNC is a no-op in FreeBSD.  It probably shouldn't be defined.
>
>???
>
>/sys/kern/vfs_vnops.c:vn_write():
>
>        if ((fp->f_flag & O_FSYNC) ||
>            (vp->v_mount && (vp->v_mount->mnt_flag & MNT_SYNCHRONOUS)))
>                ioflag |= IO_SYNC;

Oops.

So it's no illusion that fsync() is faster.  O_FSYNC prevents clustering.

Bruce

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