Re: [PATCH 1/1] xfs: fix severe performance problems when fstrimming a subset of an AG

Darrick J. Wong
2024-03-29T21:35:21Z

On Wed, Mar 27, 2024 at 04:35:12AM -0700, Christoph Hellwig wrote:
> On Tue, Mar 26, 2024 at 07:07:58PM -0700, Darrick J. Wong wrote:
> > periodically to allow other threads to do work. This implementation
> > avoids the worst problems of the original code, though it lacks the
> > desirable attribute of freeing the biggest chunks first.
>
> Do we really care much about freeing larger area first? I don't think
> it really matters for FITRIM at all.
>
> In other words, I suspect we're better off with only the by-bno
> implementation.

Welll... you could argue that if the underlying "thin provisioning" is
actually just an xfs file, that punching tons of tiny holes in that file
could increase the height of the bmbt. In that case, you'd want to
reduce the chances of the punch failing with ENOSPC by punching out
larger ranges to free up more blocks.

--D