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From: Derrick Stolee <stolee@gmail.com>
To: Jeff King <peff@peff.net>, git@vger.kernel.org
Cc: Junio C Hamano <gitster@pobox.com>
Subject: Re: [PATCH v2 09/15] rev-list: allow commit-only bitmap traversals
Date: Tue, 18 Feb 2020 13:18:21 -0500
Message-ID: <967821c8-aca4-52ff-8eb9-01a74f5a8144@gmail.com> (raw)
In-Reply-To: <20200214182227.GI150965@coredump.intra.peff.net>

On 2/14/2020 1:22 PM, Jeff King wrote:
> Here are numbers for linux.git:
> 
>   Test                         HEAD^               HEAD
>   ------------------------------------------------------------------------
>   5310.7: rev-list (commits)   8.29(8.10+0.19)       1.76(1.72+0.04) -78.8%
>   5310.8: rev-list (objects)   8.06(7.94+0.12)       8.14(7.94+0.13) +1.0%

Nice.

> That run was cheating a little, as I didn't have any commit-graph in the
> repository, and we'd built it by default these days when running git-gc.
> Here are numbers with a commit-graph:
> 
>   Test                         HEAD^               HEAD
>   ------------------------------------------------------------------------
>   5310.7: rev-list (commits)   0.70(0.58+0.12)     0.51(0.46+0.04) -27.1%
>   5310.8: rev-list (objects)   6.20(6.09+0.10)     6.27(6.16+0.11) +1.1%
> 
> Still an improvement, but a lot less impressive.

I think this is still impressive, because you are still allocating the
object structs and writing data to the output. The commit-graph code allows
cheating and doing very little work when navigating from one commit to
another. I suppose the biggest difference between these two approaches is
that the object cache contains "parsed" commits at the end (with allocated
parents and initialized commit times) and we needed a priority queue for
the commit walk. I'm impressed that this is still 27% improvement!

> diff --git a/t/t5310-pack-bitmaps.sh b/t/t5310-pack-bitmaps.sh
> index b8645ae070..2c64d0c441 100755
> --- a/t/t5310-pack-bitmaps.sh
> +++ b/t/t5310-pack-bitmaps.sh
> @@ -80,6 +80,12 @@ rev_list_tests() {
>  		test_cmp expect actual
>  	'
>  
> +	test_expect_success "enumerate commits ($state)" '
> +		git rev-list --use-bitmap-index HEAD >actual &&
> +		git rev-list HEAD >expect &&
> +		test_bitmap_traversal --no-confirm-bitmaps expect actual
> +	'
> +

I was wondering if there is anything we could add to the "expect"
command that could better guarantee these commits show up in a
different order than the bitmap order, allowing us to drop the
"--no-confirm-bitmaps". Perhaps the issue is the merge structure
of the repository, and how it will cause these orders to always
agree?

I suppose "--topo-order" may actually present an order _even closer_
to the bitmap order.

Thanks,
-Stolee

  reply index

Thread overview: 73+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-02-13  2:15 [PATCH 0/13] combining object filters and bitmaps Jeff King
2020-02-13  2:16 ` [PATCH 01/13] pack-bitmap: factor out type iterator initialization Jeff King
2020-02-13 17:45   ` Junio C Hamano
2020-02-13  2:16 ` [PATCH 02/13] pack-bitmap: fix leak of haves/wants object lists Jeff King
2020-02-13 18:12   ` Junio C Hamano
2020-02-13  2:17 ` [PATCH 03/13] rev-list: fallback to non-bitmap traversal when filtering Jeff King
2020-02-13 18:19   ` Junio C Hamano
2020-02-13 18:40     ` Jeff King
2020-02-13  2:17 ` [PATCH 04/13] rev-list: consolidate bitmap-disabling options Jeff King
2020-02-13  2:18 ` [PATCH 05/13] rev-list: factor out bitmap-optimized routines Jeff King
2020-02-13 18:34   ` Junio C Hamano
2020-02-13  2:19 ` [PATCH 06/13] rev-list: make --count work with --objects Jeff King
2020-02-13 19:14   ` Junio C Hamano
2020-02-13 20:27     ` Jeff King
2020-02-13  2:20 ` [PATCH 07/13] rev-list: allow bitmaps when counting objects Jeff King
2020-02-13 21:47   ` Junio C Hamano
2020-02-13 22:27     ` Jeff King
2020-02-13  2:20 ` [PATCH 08/13] pack-bitmap: basic noop bitmap filter infrastructure Jeff King
2020-02-13  2:21 ` [PATCH 09/13] rev-list: use bitmap filters for traversal Jeff King
2020-02-13 22:22   ` Junio C Hamano
2020-02-13 22:34     ` Jeff King
2020-02-13  2:21 ` [PATCH 10/13] bitmap: add bitmap_unset() function Jeff King
2020-02-13  2:23 ` [PATCH 11/13] pack-bitmap: implement BLOB_NONE filtering Jeff King
2020-02-13  2:25 ` [PATCH 12/13] pack-bitmap: implement BLOB_LIMIT filtering Jeff King
2020-02-13 23:17   ` Junio C Hamano
2020-02-13  2:25 ` [PATCH 13/13] pack-objects: support filters with bitmaps Jeff King
2020-02-14 18:21 ` [PATCH v2 0/15] combining object filters and bitmaps Jeff King
2020-02-14 18:22   ` [PATCH v2 01/15] pack-bitmap: factor out type iterator initialization Jeff King
2020-02-15  0:10     ` Taylor Blau
2020-02-14 18:22   ` [PATCH v2 02/15] pack-bitmap: fix leak of haves/wants object lists Jeff King
2020-02-15  0:15     ` Taylor Blau
2020-02-15  6:46       ` Jeff King
2020-02-18 17:58     ` Derrick Stolee
2020-02-18 20:02       ` Jeff King
2020-02-14 18:22   ` [PATCH v2 03/15] rev-list: fallback to non-bitmap traversal when filtering Jeff King
2020-02-15  0:22     ` Taylor Blau
2020-02-14 18:22   ` [PATCH v2 04/15] pack-bitmap: refuse to do a bitmap traversal with pathspecs Jeff King
2020-02-14 19:03     ` Junio C Hamano
2020-02-14 20:51       ` Jeff King
2020-02-14 18:22   ` [PATCH v2 05/15] rev-list: factor out bitmap-optimized routines Jeff King
2020-02-15  0:35     ` Taylor Blau
2020-02-14 18:22   ` [PATCH v2 06/15] rev-list: make --count work with --objects Jeff King
2020-02-15  0:42     ` Taylor Blau
2020-02-15  6:48       ` Jeff King
2020-02-16 23:34         ` Junio C Hamano
2020-02-18  5:24           ` Jeff King
2020-02-18 17:28             ` Junio C Hamano
2020-02-18 19:55               ` Jeff King
2020-02-18 21:19                 ` Junio C Hamano
2020-02-18 21:23                   ` Jeff King
2020-02-18 18:05     ` Derrick Stolee
2020-02-18 19:59       ` Jeff King
2020-02-14 18:22   ` [PATCH v2 07/15] rev-list: allow bitmaps when counting objects Jeff King
2020-02-15  0:45     ` Taylor Blau
2020-02-15  6:55       ` Jeff King
2020-02-16 23:36         ` Junio C Hamano
2020-02-14 18:22   ` [PATCH v2 08/15] t5310: factor out bitmap traversal comparison Jeff King
2020-02-15  2:14     ` Taylor Blau
2020-02-15  7:00       ` Jeff King
2020-02-14 18:22   ` [PATCH v2 09/15] rev-list: allow commit-only bitmap traversals Jeff King
2020-02-18 18:18     ` Derrick Stolee [this message]
2020-02-18 20:05       ` Jeff King
2020-02-18 20:11         ` Derrick Stolee
2020-02-14 18:22   ` [PATCH v2 10/15] pack-bitmap: basic noop bitmap filter infrastructure Jeff King
2020-02-14 18:22   ` [PATCH v2 11/15] rev-list: use bitmap filters for traversal Jeff King
2020-02-14 18:22   ` [PATCH v2 12/15] bitmap: add bitmap_unset() function Jeff King
2020-02-14 18:22   ` [PATCH v2 13/15] pack-bitmap: implement BLOB_NONE filtering Jeff King
2020-02-18 19:26     ` Derrick Stolee
2020-02-18 19:36       ` Derrick Stolee
2020-02-18 20:30         ` Jeff King
2020-02-18 20:24       ` Jeff King
2020-02-14 18:22   ` [PATCH v2 14/15] pack-bitmap: implement BLOB_LIMIT filtering Jeff King
2020-02-14 18:22   ` [PATCH v2 15/15] pack-objects: support filters with bitmaps Jeff King

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