On Tue, May 02, 2023 at 08:38:16AM -0700, Darrick J. Wong wrote:
> On Tue, May 02, 2023 at 12:49:44PM +0200, Carlos Maiolino wrote:
> > Hi.
> >
> > On Thu, Apr 27, 2023 at 03:45:21PM -0700, Darrick J. Wong wrote:
> > > From: Darrick J. Wong <djwong@xxxxxxxxxx>
> > >
> > > The slack calculation for per-AG btrees is a bit inaccurate because it
> > > only disables slack space in the new btrees when the amount of free
> > > space in the AG (not counting the btrees) is less than 3/32ths of the
> > > AG. In other words, it assumes that the btrees will fit in less than 9
> > > percent of the space.
> > .
> > .
> > .
> > >
> > > Signed-off-by: Darrick J. Wong <djwong@xxxxxxxxxx>
> >
> > This looks fine, with a small caveat below...
> >
> > .
> > .
> > .
> >
> > > +
> > > +static xfs_extlen_t
> > > +estimate_allocbt_blocks(
> > > + struct xfs_perag *pag,
> > > + unsigned int nr_extents)
> > > +{
> > > + return libxfs_allocbt_calc_size(pag->pag_mount, nr_extents) * 2;
> > > +}
> >
> > Forgive my ignorance here, but what's the reason of the magic number? It seems
> > to me by multiplying by 2 here, you are considering a split of every single
> > leaf for the calculated btree size, but I'm not sure if that's the intention,
> > could you please confirm or correct me? :)
>
> Ah, I should document that better...
>
> /* Account for space consumed by both free space btrees */
> return libxfs_allocbt_calc_size(...) * 2;
Thanks, can I update your patch with the above comment, or do you want to send
it again?
>
> --D
>
> > Other than that, the patch looks good
> >
> > Reviewed-by: Carlos Maiolino <cmaiolino@xxxxxxxxxx>
> >
> > --
> > Carlos Maiolino
--
Carlos Maiolino
