From: Ming Zhang <blackmagic02881@gmail.com>
To: linux-btrace@vger.kernel.org
Subject: Re: how to explain the current process?
Date: Tue, 27 Mar 2007 13:44:44 +0000 [thread overview]
Message-ID: <1175003084.3705.5.camel@dhcp-119.ibrix.com> (raw)
In-Reply-To: <1174833941.3625.10.camel@localhost.localdomain>
On Tue, 2007-03-27 at 12:58 +0200, Jens Axboe wrote:
> On Sun, Mar 25 2007, Ming Zhang wrote:
> > Hi All
> >
> > I am using blktrace to trace a untar operation on a 400GB (already 80%
> > used) ext3 disk.
> >
> > since journal in ext3 is at the beginning of ext3, so small LBA are
> > journal operations, and large lba should be inode or file data.
> >
> > 8,0 0 1081156 60.171965751 4929 P R [kjournald]
> > 8,0 0 1081157 60.171965991 4929 I W 26079 + 8 [kjournald]
> > 8,0 0 1081158 60.171966726 4929 U R [kjournald] 1
> > 8,0 0 1081159 60.171968511 4929 D W 26079 + 8 [kjournald]
> > 8,0 0 1081160 60.172249031 0 C W 26079 + 8 [0]
> >
> > journal request
> >
> > 8,0 0 1081161 60.172306613 4944 Q W 733338903 + 8 [tar]
> > 8,0 0 1081162 60.172307471 4944 G W 733338903 + 8 [tar]
> > 8,0 0 1081163 60.172308435 4944 P R [tar]
> > 8,0 0 1081164 60.172308798 4944 I W 733338903 + 8 [tar]
> > 8,0 0 1081165 60.172311794 4944 Q W 733338911 + 8 [tar]
> > 8,0 0 1081166 60.172312274 4944 M W 733338911 + 8 [tar]
> >
> > file or inode
> >
> > 8,0 0 1081167 60.172327693 4929 U R [kjournald] 1
> >
> > why here a R(read) come up? and what is the meaning of this "1" here?
>
> It's not a read, it's an UNPLUG. And the 1 means that there was 1
> request plugged when it happened.
>
> > 8,0 0 1081168 60.172329564 4929 D W 733338903 + 16
> > [kjournald]
> > 8,0 0 1081169 60.172773400 0 C W 733338903 + 16 [0]
> >
> > why it is kjounrald here to "D" this request? is this because tar
> > already "finish" the request by writing to page cache and then when do
> > device io, current process is happened to be kjournald? i read the code
> > and it grabs current pid, so it looks so. but i still need a
> > confirmation here from your guys.
>
> Because kjournald apparently ends up doing the dispatch. The unplug will
> cause dispatch of requests, and kjournald did the unplug. So it gets to
> do the dispatching as well.
>
why kjournald do the unplug? from the name i thought it is only for
journal (jbd)? then what pdflush does? thx.
Ming
next prev parent reply other threads:[~2007-03-27 13:44 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-03-25 14:45 how to explain the current process? Ming Zhang
2007-03-27 10:58 ` Jens Axboe
2007-03-27 13:44 ` Ming Zhang [this message]
2007-03-27 13:58 ` Jens Axboe
2007-03-27 14:11 ` Ming Zhang
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