Re: [PATCH 4/4] pack-bitmap: pass object filter to fill-in traversal

[Taylor Blau <me@ttaylorr.com>]

On Fri, Apr 24, 2020 at 01:42:27AM -0400, Jeff King wrote:
> On Wed, Apr 22, 2020 at 05:13:35PM -0600, Taylor Blau wrote:
>
> > From: Jeff King <peff@peff.net>
> >
> > Sometimes a bitmap traversal still has to walk some commits manually,
> > because those commits aren't included in the bitmap packfile (e.g., due
> > to a push or commit since the last full repack). If we're given an
> > object filter, we don't pass it down to this traversal. It's not
> > necessary for correctness because the bitmap code has its own filters to
> > post-process the bitmap result (which it must, to filter out the objects
> > that _are_ mentioned in the bitmapped packfile).
> >
> > And with blob filters, there was no performance reason to pass along
> > those filters, either. The fill-in traversal could omit them from the
> > result, but it wouldn't save us any time to do so, since we'd still have
> > to walk each tree entry to see if it's a blob or not.
> >
> > But now that we support tree filters, there's opportunity for savings. A
> > tree:depth=0 filter means we can avoid accessing trees entirely, since
> > we know we won't them (or any of the subtrees or blobs they point to).
>
> s/won't them/won't include them/ perhaps

Oops. Even though you wrote this patch, I clearly also should have
proofread it more carefully before sending it to the list ;).

Junio -- assuming that you are comfortable taking this series as-is (and
please let me know if you are not), would you mind fixing up this typo
as you apply it?

> > diff --git a/t/perf/p5310-pack-bitmaps.sh b/t/perf/p5310-pack-bitmaps.sh
> > index b629a211f9..95379b1d4e 100755
> > --- a/t/perf/p5310-pack-bitmaps.sh
> > +++ b/t/perf/p5310-pack-bitmaps.sh
> > @@ -95,4 +95,9 @@ test_perf 'pack to file (partial bitmap)' '
> >  	git pack-objects --use-bitmap-index --all pack2b </dev/null >/dev/null
> >  '
> >
> > +test_perf 'rev-list with tree filter (partial bitmap)' '
> > +	git rev-list --use-bitmap-index --count --objects --all \
> > +		--filter=tree:0 >/dev/null
> > +'
>
> This covers perf testing of this partial-bitmap state, but we shoudl
> make sure that we are covering correctness, too. I think so, because
> t6113 creates a similar state for all of its tests.

Yeah, we are covered there. The last three tests in t6613 cover
'--filter=tree:0', bot with and without specified objects (to make sure
that named objects don't get culled out by the filter), as well as the
'--filter=tree:1', to make sure that we didn't break that.

> -Peff

Thanks,
Taylor