Date: Thu, 21 Sep 2017 12:58:58 +0200 From: Gary Jennejohn <gljennjohn@gmail.com> To: Andreas Longwitz <longwitz@incore.de> Cc: freebsd-fs@freebsd.org Subject: Re: fsync: giving up on dirty on ufs partitions running vfs_write_suspend() Message-ID: <20170921125858.64ffe077@ernst.home> In-Reply-To: <59C37F46.80509@incore.de> References: <201709110519.v8B5JVmf060773@chez.mckusick.com> <59BD0EAC.8030206@incore.de> <20170916183117.GF78693@kib.kiev.ua> <59C37F46.80509@incore.de>
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On Thu, 21 Sep 2017 10:58:46 +0200
Andreas Longwitz <longwitz@incore.de> wrote:
[snip]
> I have checked your proposal and found that indeed the
> mnt_secondary_writes counter goes to zero when the dirties have reached
> zero. During the loop the mnt_secondary_write counter is always equal to
> one, so there is not something like a countdown and thats Kirk wanted to
> see. A dtrace output (with DELAY of 1ms in the loop) for the biggest
> loop count on a three day test is this:
>
> 18 32865 kern_unlinkat:entry path=bigfile, tid=101201,
> tid=101201, execname=rm
> 18 12747 ufs_remove:entry gj=mirror/gmbkp4p5.journal,
> inum=11155630, blocks=22301568, size=11415525660
> 18 12748 ufs_remove:return returncode=0, inum=11155630,
> blocks=22301568
> 18 18902 ffs_truncate:entry gj=mirror/gmbkp4p5.journal,
> inum=11155630, size=11415525660, mnt_flag=0x12001040,
> mnt_kern_flag=0x40006142, blocks=22301568
> 6 33304 vfs_write_suspend:entry gj=mirror/gmbkp4p5.journal,
> mnt_kern_flag=0x40006142, tid=100181
> 6 22140 vop_stdfsync:entry mounted on /home, waitfor=1,
> numoutput=0, clean=10, dirty=6, secondary_writes=1
> 10 28117 bufobj_wwait:return calls to bufobj_wait = 1,
> dirtycnt=2, secondary_writes=1
> 10 28117 bufobj_wwait:return calls to bufobj_wait = 2,
> dirtycnt=1, secondary_writes=1
> 10 28117 bufobj_wwait:return calls to bufobj_wait = 3,
> dirtycnt=1, secondary_writes=1
> 10 28117 bufobj_wwait:return calls to bufobj_wait = 4,
> dirtycnt=3, secondary_writes=1
> 10 28117 bufobj_wwait:return calls to bufobj_wait = 5,
> dirtycnt=2, secondary_writes=1
> 6 28117 bufobj_wwait:return calls to bufobj_wait = 6,
> dirtycnt=3, secondary_writes=1
> 6 28117 bufobj_wwait:return calls to bufobj_wait = 7,
> dirtycnt=3, secondary_writes=1
> 6 28117 bufobj_wwait:return calls to bufobj_wait = 8,
> dirtycnt=3, secondary_writes=1
> 6 28117 bufobj_wwait:return calls to bufobj_wait = 9,
> dirtycnt=3, secondary_writes=1
> 6 28117 bufobj_wwait:return calls to bufobj_wait = 10,
> dirtycnt=2, secondary_writes=1
> 6 28117 bufobj_wwait:return calls to bufobj_wait = 11,
> dirtycnt=2, secondary_writes=1
> 6 28117 bufobj_wwait:return calls to bufobj_wait = 12,
> dirtycnt=3, secondary_writes=1
> 6 28117 bufobj_wwait:return calls to bufobj_wait = 13,
> dirtycnt=3, secondary_writes=1
> 6 28117 bufobj_wwait:return calls to bufobj_wait = 14,
> dirtycnt=3, secondary_writes=1
> 6 28117 bufobj_wwait:return calls to bufobj_wait = 15,
> dirtycnt=4, secondary_writes=1
> 6 28117 bufobj_wwait:return calls to bufobj_wait = 16,
> dirtycnt=3, secondary_writes=1
> 6 28117 bufobj_wwait:return calls to bufobj_wait = 17,
> dirtycnt=3, secondary_writes=1
> 2 18903 ffs_truncate:return returncode=0, inum=11155630, blocks=0
> 2 32866 kern_unlinkat:return returncode=0, errno=0, number
> io's: 791/791
> 6 28117 bufobj_wwait:return calls to bufobj_wait = 18,
> dirtycnt=3, secondary_writes=0
> 6 28117 bufobj_wwait:return calls to bufobj_wait = 19,
> dirtycnt=0, secondary_writes=0
> 6 22141 vop_stdfsync:return returncode=0, pid=26, tid=100181,
> spent 240373850 nsecs
>
> So the spent time in vop_stdfsync() is 0,24 sec in the worst case I
> found using DELAY with 1 ms. I would prefer this solution. My first
> appoach (simple bumping maxres from 1000 to 100000) is also ok, but max
> spend time will be raise up to 0,5 sec. Perhaps you like something like
>
> if( maxretry < 1000 && maxretry % 10 = 0)
^ ==
> DELAY(waitns);
>
The argument to DELAY is in micro-seconds.
--
Gary Jennejohn
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