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To: Daniel Phillips <phillips@bonn-fries.net>
cc: Chris Mason <mason@suse.com>,
        James Bottomley <James.Bottomley@SteelEye.com>,
        "Stephen C. Tweedie" <sct@redhat.com>, linux-kernel@vger.kernel.org,
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Subject: Re: [PATCH] 2.4.x write barriers (updated for ext3) 
In-Reply-To: Message from Daniel Phillips <phillips@bonn-fries.net> 
   of "Mon, 04 Mar 2002 06:05:29 +0100." <E16hkfB-0000Zp-00@starship.berlin> 
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Date: Mon, 04 Mar 2002 09:03:31 -0600
From: James Bottomley <James.Bottomley@SteelEye.com>
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phillips@bonn-fries.net said:
> But chances are, almost all the IOs ahead of the journal commit belong
> to your same filesystem anyway, so you may be worrying too much about
> possibly waiting for something on another partition. 

My impression is that most modern JFS can work on multiple transactions 
simultaneously.  All you really care about, I believe, is I/O ordering within 
the transaction.  However, separate transactions have no I/O ordering 
requirements with respect to each other (unless they actually overlap).  Using 
ordered tags imposes a global ordering, not just a local transaction ordering, 
so they may not be the most appropriate way to ensure the ordering of writes 
within a single transaction.

I'm not really a JFS expert, so perhaps those who actually develop these 
filesystems could comment?

James


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