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Re: [RFC] Delayed logging

To: Christoph Hellwig <hch@xxxxxxxxxxxxx>
Subject: Re: [RFC] Delayed logging
From: Dave Chinner <david@xxxxxxxxxxxxx>
Date: Tue, 16 Mar 2010 12:14:03 +1100
Cc: xfs@xxxxxxxxxxx
In-reply-to: <20100315160801.GB10406@xxxxxxxxxxxxx>
References: <20100315043000.GK4732@dastard> <20100315160801.GB10406@xxxxxxxxxxxxx>
User-agent: Mutt/1.5.20 (2009-06-14)
On Mon, Mar 15, 2010 at 12:08:01PM -0400, Christoph Hellwig wrote:
> Some comments on the patches:
>  - "xfs: cluster fsync transaction" seems like something that can stand
>    on it's own and go into the tree now.  Despite the comments it
>    currently only clusters in fsync and not write_inode which might
>    lead to higher benefits, btw.

As I said, I'll have a bit more of a think about this one...

>  - the busy extent tracking might be worth to be reordered before the
>    delayed logging series.  In itself it might also want some reordering
>    as there's a lot churn in the patches there.  Making
>    "XFS: Simplify transaction busy extent tracking" first in that
>    subseries might help quite a bit to reduce that churn

Agreed. They were ordered this way because I only added the extent
tracking after doing the delayed logging and tracking down one of
the sources of log forces that was limiting performance was
overflowing the per-ag busy extent array. I'll rework it....

>  - The actual CIL implementation seems to be split into too small
>    patches IMHO.  E.g. "xfs: extend the log item to support delayed
>    logging" and "xfs: Introduce the Committed Item List" are two
>    sides of the same coin and splitting it might not make too much
>    sense.

True, it might be a bit fine grained. Really, what I wanted to do is
split the changes that affected the non-delayed logging from those
that are only executed when delayed logging is active. That way I
could confirm that the non-delayed path was still operating
correctly before adding all the delayed logging code that used
it. I can combine them together again if you want.


Dave Chinner

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