From: Derrick Stolee <stolee@gmail.com>
To: Taylor Blau <me@ttaylorr.com>, git@vger.kernel.org
Cc: peff@peff.net, jrnieder@gmail.com
Subject: Re: [PATCH 00/20] pack-revindex: prepare for on-disk reverse index
Date: Mon, 11 Jan 2021 07:07:17 -0500 [thread overview]
Message-ID: <75ba9979-1a1f-de9f-c2cc-1433d30ed09d@gmail.com> (raw)
In-Reply-To: <cover.1610129796.git.me@ttaylorr.com>
On 1/8/2021 1:16 PM, Taylor Blau wrote:
...
> - First, a new API is proposed.
>
> - Then, uses of the old API are removed one by one and replaced with their
> new counterparts.
>
> - Finally, without any callers remaining, the old API is removed.
This patch series has a clear layout that was easy to follow.
In a vacuum, the conversions from immediate struct member lookups
to API calls seems like adding overhead to something that is done
frequently in a loop. However, you do justify it:
> Generating the reverse index in memory for repositories with large packs has two
> significant drawbacks:
>
> - It requires allocating sizeof(struct revindex_entry) per packed object.
>
> - It requires us to sort the entries by their pack offset. This is implemented
> in sort_revindex() using a radix sort, but still takes considerable time (as
> benchmarks found in the second series demonstrate).
>
> Both of these can be addressed by storing the reverse index in a new '.rev' file
> alongside the packs. This file is written once (during pack creation), and does
> not require sorting when accessed, since it is stored in a sorted order.
Even if these method calls do add a bit of overhead to each
access, it helps to not compute the table from scratch before
any access is possible.
This will be particularly valuable for operations that use only
a few position lookups, such as "is object A reachable from
commit C?"
Operations that iterate through every object in a bitmap are
more likely to notice a difference, but that will probably be
visible in the next series.
My comments on this series are very minor.
I made only one comment about "if (method() < 0)" versus
"if (method())" but that pattern appears in multiple patches.
_If_ you decide to change that pattern, then I'm sure you can
find all uses.
Reviewed-by: Derrick Stolee <dstolee@microsoft.com>
Thanks,
-Stolee
next prev parent reply other threads:[~2021-01-11 12:08 UTC|newest]
Thread overview: 121+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-08 18:16 [PATCH 00/20] pack-revindex: prepare for on-disk reverse index Taylor Blau
2021-01-08 18:16 ` [PATCH 01/20] pack-revindex: introduce a new API Taylor Blau
2021-01-12 8:41 ` Jeff King
2021-01-12 9:41 ` Jeff King
2021-01-12 16:27 ` Taylor Blau
2021-01-13 8:06 ` Junio C Hamano
2021-01-13 8:54 ` Junio C Hamano
2021-01-13 13:17 ` Jeff King
2021-01-13 16:23 ` Taylor Blau
2021-01-08 18:16 ` [PATCH 02/20] write_reuse_object(): convert to new revindex API Taylor Blau
2021-01-12 8:47 ` Jeff King
2021-01-12 16:31 ` Taylor Blau
2021-01-13 13:02 ` Jeff King
2021-01-08 18:16 ` [PATCH 03/20] write_reused_pack_one(): " Taylor Blau
2021-01-12 8:50 ` Jeff King
2021-01-12 16:34 ` Taylor Blau
2021-01-08 18:16 ` [PATCH 04/20] write_reused_pack_verbatim(): " Taylor Blau
2021-01-12 8:50 ` Jeff King
2021-01-08 18:17 ` [PATCH 05/20] check_object(): " Taylor Blau
2021-01-11 11:43 ` Derrick Stolee
2021-01-11 16:15 ` Taylor Blau
2021-01-12 8:54 ` Jeff King
2021-01-12 8:51 ` Jeff King
2021-01-08 18:17 ` [PATCH 06/20] bitmap_position_packfile(): " Taylor Blau
2021-01-08 18:17 ` [PATCH 07/20] show_objects_for_type(): " Taylor Blau
2021-01-12 8:57 ` Jeff King
2021-01-12 16:35 ` Taylor Blau
2021-01-08 18:17 ` [PATCH 08/20] get_size_by_pos(): " Taylor Blau
2021-01-08 18:17 ` [PATCH 09/20] try_partial_reuse(): " Taylor Blau
2021-01-12 9:06 ` Jeff King
2021-01-12 16:47 ` Taylor Blau
2021-01-08 18:17 ` [PATCH 10/20] rebuild_existing_bitmaps(): " Taylor Blau
2021-01-08 18:17 ` [PATCH 11/20] get_delta_base_oid(): " Taylor Blau
2021-01-08 18:17 ` [PATCH 12/20] retry_bad_packed_offset(): " Taylor Blau
2021-01-08 18:17 ` [PATCH 13/20] packed_object_info(): " Taylor Blau
2021-01-12 9:11 ` Jeff King
2021-01-12 16:51 ` Taylor Blau
2021-01-08 18:17 ` [PATCH 14/20] unpack_entry(): " Taylor Blau
2021-01-12 9:22 ` Jeff King
2021-01-12 16:56 ` Taylor Blau
2021-01-08 18:17 ` [PATCH 15/20] for_each_object_in_pack(): " Taylor Blau
2021-01-08 18:17 ` [PATCH 16/20] builtin/gc.c: guess the size of the revindex Taylor Blau
2021-01-11 11:52 ` Derrick Stolee
2021-01-11 16:23 ` Taylor Blau
2021-01-11 17:09 ` Derrick Stolee
2021-01-12 9:28 ` Jeff King
2021-01-08 18:17 ` [PATCH 17/20] pack-revindex: remove unused 'find_pack_revindex()' Taylor Blau
2021-01-08 18:17 ` [PATCH 18/20] pack-revindex: remove unused 'find_revindex_position()' Taylor Blau
2021-01-11 11:57 ` Derrick Stolee
2021-01-11 16:27 ` Taylor Blau
2021-01-11 17:11 ` Derrick Stolee
2021-01-12 9:32 ` Jeff King
2021-01-12 16:59 ` Taylor Blau
2021-01-13 13:05 ` Jeff King
2021-01-08 18:18 ` [PATCH 19/20] pack-revindex: hide the definition of 'revindex_entry' Taylor Blau
2021-01-11 11:57 ` Derrick Stolee
2021-01-12 9:34 ` Jeff King
2021-01-08 18:18 ` [PATCH 20/20] pack-revindex.c: avoid direct revindex access in 'offset_to_pack_pos()' Taylor Blau
2021-01-12 9:37 ` Jeff King
2021-01-12 17:02 ` Taylor Blau
2021-01-11 12:07 ` Derrick Stolee [this message]
2021-01-11 16:30 ` [PATCH 00/20] pack-revindex: prepare for on-disk reverse index Taylor Blau
2021-01-11 17:15 ` Derrick Stolee
2021-01-11 17:29 ` Taylor Blau
2021-01-11 18:40 ` Junio C Hamano
2021-01-12 9:45 ` Jeff King
2021-01-12 17:07 ` Taylor Blau
2021-01-13 0:23 ` Junio C Hamano
2021-01-13 0:52 ` Taylor Blau
2021-01-13 2:15 ` Junio C Hamano
2021-01-13 3:23 ` Taylor Blau
2021-01-13 8:21 ` Junio C Hamano
2021-01-13 13:13 ` Jeff King
2021-01-13 15:34 ` Taylor Blau
2021-01-13 20:06 ` Junio C Hamano
2021-01-13 20:13 ` Taylor Blau
2021-01-13 20:22 ` Jeff King
2021-01-13 22:23 ` [PATCH v2 " Taylor Blau
2021-01-13 22:23 ` [PATCH v2 01/20] pack-revindex: introduce a new API Taylor Blau
2021-01-14 6:46 ` Junio C Hamano
2021-01-14 12:00 ` Derrick Stolee
2021-01-14 17:06 ` Taylor Blau
2021-01-14 19:19 ` Jeff King
2021-01-14 20:47 ` Junio C Hamano
2021-01-13 22:23 ` [PATCH v2 02/20] write_reuse_object(): convert to new revindex API Taylor Blau
2021-01-13 22:23 ` [PATCH v2 03/20] write_reused_pack_one(): " Taylor Blau
2021-01-13 22:23 ` [PATCH v2 04/20] write_reused_pack_verbatim(): " Taylor Blau
2021-01-13 22:23 ` [PATCH v2 05/20] check_object(): " Taylor Blau
2021-01-13 22:23 ` [PATCH v2 06/20] bitmap_position_packfile(): " Taylor Blau
2021-01-13 22:23 ` [PATCH v2 07/20] show_objects_for_type(): " Taylor Blau
2021-01-13 22:24 ` [PATCH v2 08/20] get_size_by_pos(): " Taylor Blau
2021-01-13 22:24 ` [PATCH v2 09/20] try_partial_reuse(): " Taylor Blau
2021-01-13 22:24 ` [PATCH v2 10/20] rebuild_existing_bitmaps(): " Taylor Blau
2021-01-13 22:24 ` [PATCH v2 11/20] get_delta_base_oid(): " Taylor Blau
2021-01-13 22:24 ` [PATCH v2 12/20] retry_bad_packed_offset(): " Taylor Blau
2021-01-13 22:24 ` [PATCH v2 13/20] packed_object_info(): " Taylor Blau
2021-01-13 22:24 ` [PATCH v2 14/20] unpack_entry(): " Taylor Blau
2021-01-13 22:24 ` [PATCH v2 15/20] for_each_object_in_pack(): " Taylor Blau
2021-01-14 6:43 ` Junio C Hamano
2021-01-14 17:00 ` Taylor Blau
2021-01-14 19:33 ` Jeff King
2021-01-14 20:11 ` Jeff King
2021-01-14 20:15 ` Taylor Blau
2021-01-15 2:22 ` Junio C Hamano
2021-01-15 2:29 ` Taylor Blau
2021-01-14 20:51 ` Junio C Hamano
2021-01-13 22:24 ` [PATCH v2 16/20] builtin/gc.c: guess the size of the revindex Taylor Blau
2021-01-14 6:33 ` Junio C Hamano
2021-01-14 16:53 ` Taylor Blau
2021-01-14 19:43 ` Jeff King
2021-01-13 22:24 ` [PATCH v2 17/20] pack-revindex: remove unused 'find_pack_revindex()' Taylor Blau
2021-01-13 22:25 ` [PATCH v2 18/20] pack-revindex: remove unused 'find_revindex_position()' Taylor Blau
2021-01-14 6:42 ` Junio C Hamano
2021-01-13 22:25 ` [PATCH v2 19/20] pack-revindex: hide the definition of 'revindex_entry' Taylor Blau
2021-01-13 22:25 ` [PATCH v2 20/20] pack-revindex.c: avoid direct revindex access in 'offset_to_pack_pos()' Taylor Blau
2021-01-14 6:42 ` Junio C Hamano
2021-01-14 16:56 ` Taylor Blau
2021-01-14 19:51 ` [PATCH v2 00/20] pack-revindex: prepare for on-disk reverse index Jeff King
2021-01-14 20:53 ` Junio C Hamano
2021-01-15 9:32 ` Jeff King
2021-01-15 9:33 ` Jeff King
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