From: Taylor Blau <me@ttaylorr.com>
To: Jeff King <peff@peff.net>, Junio C Hamano <gitster@pobox.com>
Cc: git@vger.kernel.org, Jeff King <peff@peff.net>,
Derrick Stolee <derrickstolee@github.com>
Subject: Re: [PATCH 3/3] pack-bitmap.c: use commit boundary during bitmap traversal
Date: Wed, 3 May 2023 17:42:25 -0400 [thread overview]
Message-ID: <ZFLVQdjXoEmGImml@nand.local> (raw)
In-Reply-To: <xmqqh6t3ztee.fsf@gitster.g>
On Tue, Apr 25, 2023 at 11:52:25AM -0700, Junio C Hamano wrote:
> Taylor Blau <me@ttaylorr.com> writes:
>
> > 3. Fall back to the ordinary object traversal if either (a) there are
> > no haves, (b) none of the haves are in the bitmapped pack or MIDX,
> > or (c) there are no wants.
>
> Tangents. If there are no haves, wouldn't the answer by definition
> everything that are reachable from all wants? Is there a reason why
> a bitmapped walk cannot fulfill such a request? If there are no
> wants, wouldn't the answer by definition an empty set? Again, I am
> not sure what the ordinary object traversal is expected to do in
> such a case.
Oops, (a) is just wrong. The old code is:
/*
* if we have a HAVES list, but none of those haves is contained
* in the packfile that has a bitmap, we don't have anything to
* optimize here
*/
if (haves && !in_bitmapped_pack(bitmap_git, haves))
goto cleanup;
which is itself an iffy optimization that I have toyed with the idea of
getting rid of over the years, since I am skeptical that it is doing
much even in the classic bitmap traversal.
But we only do that in_bitmapped_pack() if there are haves to begin
with, so (a) from my commit message is incorrect. Sorry about that.
> > And is more-or-less equivalent to using the *old* algorithm with this
> > invocation:
> >
> > $ git rev-list --objects --boundary $WANTS --not $HAVES |
>
> It is especially confusing because the "--boundary" (at least as I
> originally had invented it), i.e. a commit that is smudged with
> UNINTERESTING bit, whose parent we did not bother to dig further to
> paint with the same UNINTERESTING bit, is not something we start our
> computation with; it is something we learn _after_ completing the
> history traversing. So I am utterly confused X-<.
Hmm. This is from code that Peff and I wrote together a long time ago.
My recollection is that we only care about the UNINTERESTING commits
between the tips and boundary (as you described it), but no further, and
that we could discover that set during limit_list() alone.
But maybe not? I honestly cannot remember. Perhaps Peff does?
Thanks,
Taylor
next prev parent reply other threads:[~2023-05-03 21:42 UTC|newest]
Thread overview: 51+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-04-25 0:00 [PATCH 0/3] pack-bitmap: boundary-based bitmap traversal Taylor Blau
2023-04-25 0:00 ` [PATCH 1/3] revision: support tracking uninteresting commits Taylor Blau
2023-04-25 18:15 ` Derrick Stolee
2023-05-03 21:48 ` Taylor Blau
2023-05-04 13:46 ` Derrick Stolee
2023-05-03 22:08 ` Taylor Blau
2023-05-04 13:59 ` Derrick Stolee
2023-05-05 17:30 ` Taylor Blau
2023-04-25 18:22 ` Junio C Hamano
2023-04-25 18:48 ` Taylor Blau
2023-04-25 0:00 ` [PATCH 2/3] pack-bitmap.c: extract `fill_in_bitmap()` Taylor Blau
2023-04-25 18:32 ` Junio C Hamano
2023-04-25 18:51 ` [PATCH 2/3] pack-bitmap.c: extract `fill_in_bitmap()`t Taylor Blau
2023-04-25 0:00 ` [PATCH 3/3] pack-bitmap.c: use commit boundary during bitmap traversal Taylor Blau
2023-04-25 18:52 ` Junio C Hamano
2023-05-02 21:31 ` Felipe Contreras
2023-05-03 21:42 ` Taylor Blau [this message]
2023-05-03 21:58 ` Junio C Hamano
2023-04-25 18:53 ` Derrick Stolee
2023-04-25 18:02 ` [PATCH 0/3] pack-bitmap: boundary-based " Junio C Hamano
2023-04-25 18:30 ` Derrick Stolee
2023-04-25 18:57 ` Taylor Blau
2023-04-25 19:52 ` Derrick Stolee
2023-05-03 21:43 ` Taylor Blau
2023-04-25 18:06 ` Derrick Stolee
2023-04-25 19:01 ` Taylor Blau
2023-04-25 20:27 ` Derrick Stolee
2023-05-01 22:08 ` Junio C Hamano
2023-05-02 23:52 ` Taylor Blau
2023-05-05 17:27 ` [PATCH v2 0/2] " Taylor Blau
2023-05-05 17:27 ` [PATCH v2 1/2] pack-bitmap.c: extract `fill_in_bitmap()` Taylor Blau
2023-05-05 17:27 ` [PATCH v2 2/2] pack-bitmap.c: use commit boundary during bitmap traversal Taylor Blau
2023-05-05 18:13 ` Derrick Stolee
2023-05-05 18:43 ` Taylor Blau
2023-05-05 17:33 ` [PATCH v2 0/2] pack-bitmap: boundary-based " Junio C Hamano
2023-05-05 17:59 ` Derrick Stolee
2023-05-05 18:46 ` [PATCH v2 0/2] pack-bitmap: boundary-based bitmap traversalt Taylor Blau
2023-05-05 20:45 ` Derrick Stolee
2023-05-08 17:38 ` [PATCH v3 0/3] pack-bitmap: boundary-based bitmap traversal Taylor Blau
2023-05-08 17:38 ` [PATCH v3 1/3] object: add object_array initializer helper function Taylor Blau
2023-05-08 17:38 ` [PATCH v3 2/3] pack-bitmap.c: extract `fill_in_bitmap()` Taylor Blau
2023-05-08 17:38 ` [PATCH v3 3/3] pack-bitmap.c: use commit boundary during bitmap traversal Taylor Blau
2023-05-08 20:53 ` Derrick Stolee
2023-05-08 22:12 ` Taylor Blau
2023-05-10 22:55 ` [PATCH v3 0/3] pack-bitmap: boundary-based " Junio C Hamano
2023-05-10 23:10 ` Taylor Blau
2023-05-11 15:23 ` Derrick Stolee
2023-06-08 16:25 ` [PATCH v4 " Taylor Blau
2023-06-08 16:25 ` [PATCH v4 1/3] object: add object_array initializer helper function Taylor Blau
2023-06-08 16:25 ` [PATCH v4 2/3] pack-bitmap.c: extract `fill_in_bitmap()` Taylor Blau
2023-06-08 16:25 ` [PATCH v4 3/3] pack-bitmap.c: use commit boundary during bitmap traversal Taylor Blau
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