From: Junio C Hamano <gitster@pobox.com>
To: Jeff King <peff@peff.net>
Cc: Taylor Blau <me@ttaylorr.com>,
git@vger.kernel.org, dstolee@microsoft.com, jrnieder@gmail.com
Subject: Re: [PATCH v2 01/20] pack-revindex: introduce a new API
Date: Thu, 14 Jan 2021 12:47:31 -0800 [thread overview]
Message-ID: <xmqq35z3xn30.fsf@gitster.c.googlers.com> (raw)
In-Reply-To: <YACZLHm4NtrM3POZ@coredump.intra.peff.net> (Jeff King's message of "Thu, 14 Jan 2021 14:19:08 -0500")
Jeff King <peff@peff.net> writes:
> On Thu, Jan 14, 2021 at 12:06:20PM -0500, Taylor Blau wrote:
>
>> > > + * This function runs in time O(log N) with the number of objects in the pack.
>> >
>> > Is it a good idea to commit to such performance characteristics as a
>> > promise to callers like this (the comment applies to all three
>> > functions)?
>> >
>> > It depends on how a developer is helped by this comment when
>> > deciding whether to use this function, or find other ways, to
>> > implement what s/he wants to do.
>>
>> I don't mind it. If they all had the same performance characteristics, I
>> wouldn't be for it, but since they don't, I think that it's good to
>> know. Peff suggested this back in [1].
>
> Yeah, I asked for this. As somebody who has frequently worked on the
> code which accesses the revindex (mostly bitmap stuff), I found it
> useful to understand how expensive the operations were. However, I also
> know what their runtimes are at this point, and it is not like somebody
> interested cannot look at the implementation. So it may not be that
> important.
>
> So I do still think it is useful, but if somebody feels strongly against
> it, I don't mind it being removed.
That won't be me. It's not like you'd use pack_pos_to_index()
combined with pack_pos_to_offset() instead of offset_to_pack_pos()
because the latter is more expensive than using the other two
functions; the comment does not help those who want to know relative
performance of these functions for such a purpose.
I was just curious who the comments were meant to help, that's all.
Thanks.
next prev parent reply other threads:[~2021-01-14 20:48 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 ` [PATCH 00/20] pack-revindex: prepare for on-disk reverse index Derrick Stolee
2021-01-11 16:30 ` 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 [this message]
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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