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Date: Tue, 28 Nov 2023 09:02:22 -0800
From: "Darrick J. Wong" <djwong@kernel.org>
To: Christoph Hellwig <hch@infradead.org>
Cc: Dave Chinner <dchinner@redhat.com>, linux-xfs@vger.kernel.org
Subject: Re: [PATCH 5/7] xfs: implement block reservation accounting for
 btrees we're staging
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On Mon, Nov 27, 2023 at 09:41:28PM -0800, Christoph Hellwig wrote:
> On Mon, Nov 27, 2023 at 02:34:51PM -0800, Darrick J. Wong wrote:
> > That had a noticeable effect on performance straight after mounting
> > because touching /any/ btree would result in splits.  IIRC Dave and I
> > decided that repair should generate btree blocks that were 75% full
> > unless space was tight.  We defined tight as ~10% free to avoid repair
> > failures and settled on 3/32 to avoid div64.
> > 
> > IOWs, we mostly pulled it out of thin air. ;)
> 
> Maybe throw a little comment about this in.

Yeah, I'll paste the sordid history into the commit message when I
change the code to use div_u64.

--D