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From: Taylor Blau <me@ttaylorr.com>
To: "Ævar Arnfjörð Bjarmason" <avarab@gmail.com>
Cc: git@vger.kernel.org, Junio C Hamano <gitster@pobox.com>,
	Jeff King <peff@peff.net>, Taylor Blau <me@ttaylorr.com>,
	Derrick Stolee <dstolee@microsoft.com>
Subject: Re: [PATCH] pack-write: skip *.rev work when not writing *.rev
Date: Tue, 7 Sep 2021 22:50:58 -0400	[thread overview]
Message-ID: <YTglEreI7nFCII/b@nand.local> (raw)
In-Reply-To: <patch-1.1-366ba928bd-20210908T010743Z-avarab@gmail.com>

On Wed, Sep 08, 2021 at 03:08:03AM +0200, Ævar Arnfjörð Bjarmason wrote:
> Fix a performance regression introduced in a587b5a786 (pack-write.c:
> extract 'write_rev_file_order', 2021-03-30) and stop needlessly
> allocating the "pack_order" array and sorting it with
> "pack_order_cmp()", only to throw that work away when we discover that
> we're not writing *.rev files after all.
>
> This redundant work was not present in the original version of this
> code added in 8ef50d9958 (pack-write.c: prepare to write 'pack-*.rev'
> files, 2021-01-25). There we'd call write_rev_file() from
> e.g. finish_tmp_packfile(), but we'd "return NULL" early in
> write_rev_file() if not doing a "WRITE_REV" or "WRITE_REV_VERIFY".
>
> Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
> ---
>  pack-write.c | 3 +++
>  1 file changed, 3 insertions(+)
>
> diff --git a/pack-write.c b/pack-write.c
> index f1fc3ecafa..1883848e7c 100644
> --- a/pack-write.c
> +++ b/pack-write.c
> @@ -224,6 +224,9 @@ const char *write_rev_file(const char *rev_name,
>  	uint32_t i;
>  	const char *ret;
>
> +	if (!(flags & WRITE_REV) && !(flags & WRITE_REV_VERIFY))
> +		return NULL;
> +

Great catch! This fix as-is is obviously correct, but it does make the
same checks in write_rev_file_order redundant as a result.

If we call write_rev_file() without WRITE_REV, then we'll never call
write_rev_file_order(). The other caller of write_rev_file_order() is
from midx.c:write_midx_reverse_index(), which is only called by
write_midx_internal() where it is guarded by a similar conditional.

So I think we could probably either:

  - remove the check from write_rev_file_order() altogether, moving it
    to write_rev_file() like you did here, or

  - remove the check from write_rev_file_order() and elevate it to the
    caller which is missing the check in finish_tmp_packfile()

Of the two, I think the former is more appealing (since no other
functions called by finish_tmp_packfile() are guarded like that; they
conditionally behave as noops depending on `flags`).

But what you wrote here is just fine as-is, so the above are just some
optional ideas for potential improvements.

Thanks,
Taylor

  parent reply	other threads:[~2021-09-08  2:51 UTC|newest]

Thread overview: 171+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-02-10 23:02 [PATCH 0/9] midx: implement a multi-pack reverse index Taylor Blau
2021-02-10 23:02 ` [PATCH 1/9] t/helper/test-read-midx.c: add '--show-objects' Taylor Blau
2021-02-11  2:27   ` Derrick Stolee
2021-02-11  2:34     ` Taylor Blau
2021-02-10 23:02 ` [PATCH 2/9] midx: allow marking a pack as preferred Taylor Blau
2021-02-11 19:33   ` SZEDER Gábor
2021-02-15 15:49     ` Taylor Blau
2021-02-15 17:01       ` Ævar Arnfjörð Bjarmason
2021-02-15 18:41         ` [PATCH 0/5] commit-graph: parse_options() cleanup Ævar Arnfjörð Bjarmason
2021-02-15 18:41         ` [PATCH 1/5] commit-graph: define common usage with a macro Ævar Arnfjörð Bjarmason
2021-02-16 11:33           ` Derrick Stolee
2021-02-15 18:41         ` [PATCH 2/5] commit-graph: remove redundant handling of -h Ævar Arnfjörð Bjarmason
2021-02-16 11:35           ` Derrick Stolee
2021-02-15 18:41         ` [PATCH 3/5] commit-graph: use parse_options_concat() Ævar Arnfjörð Bjarmason
2021-02-15 18:51           ` Taylor Blau
2021-02-15 19:53             ` Taylor Blau
2021-02-15 20:39             ` Ævar Arnfjörð Bjarmason
2021-09-17 21:13               ` SZEDER Gábor
2021-09-17 22:03                 ` Jeff King
2021-09-18  4:30                   ` Taylor Blau
2021-09-18  7:20                     ` Ævar Arnfjörð Bjarmason
2021-09-18 15:56                       ` Taylor Blau
2021-09-18 15:58                         ` Taylor Blau
2021-09-18  0:58                 ` Ævar Arnfjörð Bjarmason
2021-02-15 18:41         ` [PATCH 4/5] commit-graph: refactor dispatch loop for style Ævar Arnfjörð Bjarmason
2021-02-15 18:53           ` Taylor Blau
2021-02-16 11:40             ` Derrick Stolee
2021-02-16 12:02               ` Ævar Arnfjörð Bjarmason
2021-02-16 18:28                 ` Derrick Stolee
2021-02-15 18:41         ` [PATCH 5/5] commit-graph: show usage on "commit-graph [write|verify] garbage" Ævar Arnfjörð Bjarmason
2021-02-15 19:06           ` Taylor Blau
2021-02-16 11:43           ` Derrick Stolee
2021-02-15 21:01         ` [PATCH v2 0/4] midx: split out sub-commands Taylor Blau
2021-02-15 21:01           ` [PATCH v2 1/4] builtin/multi-pack-index.c: inline 'flags' with options Taylor Blau
2021-02-15 21:01           ` [PATCH v2 2/4] builtin/multi-pack-index.c: don't handle 'progress' separately Taylor Blau
2021-02-15 21:39             ` Ævar Arnfjörð Bjarmason
2021-02-15 21:45               ` Taylor Blau
2021-02-16 11:47                 ` Derrick Stolee
2021-02-15 21:01           ` [PATCH v2 3/4] builtin/multi-pack-index.c: define common usage with a macro Taylor Blau
2021-02-15 21:01           ` [PATCH v2 4/4] builtin/multi-pack-index.c: split sub-commands Taylor Blau
2021-02-15 21:54             ` Ævar Arnfjörð Bjarmason
2021-02-15 22:34               ` Taylor Blau
2021-02-15 23:11                 ` Ævar Arnfjörð Bjarmason
2021-02-15 23:49                   ` Taylor Blau
2021-02-16 11:50           ` [PATCH v2 0/4] midx: split out sub-commands Derrick Stolee
2021-02-16 14:28             ` Taylor Blau
2021-02-10 23:02 ` [PATCH 3/9] midx: don't free midx_name early Taylor Blau
2021-02-10 23:02 ` [PATCH 4/9] midx: keep track of the checksum Taylor Blau
2021-02-11  2:33   ` Derrick Stolee
2021-02-11  2:35     ` Taylor Blau
2021-02-10 23:03 ` [PATCH 5/9] midx: make some functions non-static Taylor Blau
2021-02-10 23:03 ` [PATCH 6/9] Documentation/technical: describe multi-pack reverse indexes Taylor Blau
2021-02-11  2:48   ` Derrick Stolee
2021-02-11  3:03     ` Taylor Blau
2021-02-10 23:03 ` [PATCH 7/9] pack-revindex: read " Taylor Blau
2021-02-11  2:53   ` Derrick Stolee
2021-02-11  3:04     ` Taylor Blau
2021-02-11  7:54   ` Junio C Hamano
2021-02-11 14:54     ` Taylor Blau
2021-02-10 23:03 ` [PATCH 8/9] pack-write.c: extract 'write_rev_file_order' Taylor Blau
2021-02-10 23:03 ` [PATCH 9/9] pack-revindex: write multi-pack reverse indexes Taylor Blau
2021-02-11  2:58 ` [PATCH 0/9] midx: implement a multi-pack reverse index Derrick Stolee
2021-02-11  3:06   ` Taylor Blau
2021-02-11  8:13 ` Junio C Hamano
2021-02-11 18:37   ` Derrick Stolee
2021-02-11 18:55     ` Junio C Hamano
2021-02-24 19:09 ` [PATCH v2 00/15] " Taylor Blau
2021-02-24 19:09   ` [PATCH v2 01/15] builtin/multi-pack-index.c: inline 'flags' with options Taylor Blau
2021-02-24 19:09   ` [PATCH v2 02/15] builtin/multi-pack-index.c: don't handle 'progress' separately Taylor Blau
2021-02-24 19:09   ` [PATCH v2 03/15] builtin/multi-pack-index.c: define common usage with a macro Taylor Blau
2021-02-24 19:09   ` [PATCH v2 04/15] builtin/multi-pack-index.c: split sub-commands Taylor Blau
2021-03-02  4:06     ` Jonathan Tan
2021-03-02 19:02       ` Taylor Blau
2021-03-04  1:54         ` Jonathan Tan
2021-03-04  3:02           ` Taylor Blau
2021-02-24 19:09   ` [PATCH v2 05/15] builtin/multi-pack-index.c: don't enter bogus cmd_mode Taylor Blau
2021-02-24 19:09   ` [PATCH v2 06/15] builtin/multi-pack-index.c: display usage on unrecognized command Taylor Blau
2021-02-24 19:09   ` [PATCH v2 07/15] t/helper/test-read-midx.c: add '--show-objects' Taylor Blau
2021-02-24 19:09   ` [PATCH v2 08/15] midx: allow marking a pack as preferred Taylor Blau
2021-03-02  4:17     ` Jonathan Tan
2021-03-02 19:09       ` Taylor Blau
2021-03-04  2:00         ` Jonathan Tan
2021-03-04  3:04           ` Taylor Blau
2021-02-24 19:09   ` [PATCH v2 09/15] midx: don't free midx_name early Taylor Blau
2021-02-24 19:10   ` [PATCH v2 10/15] midx: keep track of the checksum Taylor Blau
2021-02-24 19:10   ` [PATCH v2 11/15] midx: make some functions non-static Taylor Blau
2021-02-24 19:10   ` [PATCH v2 12/15] Documentation/technical: describe multi-pack reverse indexes Taylor Blau
2021-03-02  4:21     ` Jonathan Tan
2021-03-02  4:36       ` Taylor Blau
2021-03-02 19:15       ` Taylor Blau
2021-03-04  2:03         ` Jonathan Tan
2021-02-24 19:10   ` [PATCH v2 13/15] pack-revindex: read " Taylor Blau
2021-03-02 18:36     ` Jonathan Tan
2021-03-03 15:27       ` Taylor Blau
2021-02-24 19:10   ` [PATCH v2 14/15] pack-write.c: extract 'write_rev_file_order' Taylor Blau
2021-02-24 19:10   ` [PATCH v2 15/15] pack-revindex: write multi-pack reverse indexes Taylor Blau
2021-03-02 18:40     ` Jonathan Tan
2021-03-03 15:30       ` Taylor Blau
2021-03-04  2:04         ` Jonathan Tan
2021-03-04  3:06           ` Taylor Blau
2021-03-11 17:04 ` [PATCH v3 00/16] midx: implement a multi-pack reverse index Taylor Blau
2021-03-11 17:04   ` [PATCH v3 01/16] builtin/multi-pack-index.c: inline 'flags' with options Taylor Blau
2021-03-29 11:20     ` Jeff King
2021-03-11 17:04   ` [PATCH v3 02/16] builtin/multi-pack-index.c: don't handle 'progress' separately Taylor Blau
2021-03-29 11:22     ` Jeff King
2021-03-11 17:04   ` [PATCH v3 03/16] builtin/multi-pack-index.c: define common usage with a macro Taylor Blau
2021-03-11 17:04   ` [PATCH v3 04/16] builtin/multi-pack-index.c: split sub-commands Taylor Blau
2021-03-29 11:36     ` Jeff King
2021-03-29 20:38       ` Taylor Blau
2021-03-30  7:04         ` Jeff King
2021-03-11 17:04   ` [PATCH v3 05/16] builtin/multi-pack-index.c: don't enter bogus cmd_mode Taylor Blau
2021-03-11 17:04   ` [PATCH v3 06/16] builtin/multi-pack-index.c: display usage on unrecognized command Taylor Blau
2021-03-29 11:42     ` Jeff King
2021-03-29 20:41       ` Taylor Blau
2021-03-11 17:05   ` [PATCH v3 07/16] t/helper/test-read-midx.c: add '--show-objects' Taylor Blau
2021-03-11 17:05   ` [PATCH v3 08/16] midx: allow marking a pack as preferred Taylor Blau
2021-03-29 12:00     ` Jeff King
2021-03-29 21:15       ` Taylor Blau
2021-03-30  7:11         ` Jeff King
2021-03-11 17:05   ` [PATCH v3 09/16] midx: don't free midx_name early Taylor Blau
2021-03-11 17:05   ` [PATCH v3 10/16] midx: keep track of the checksum Taylor Blau
2021-03-11 17:05   ` [PATCH v3 11/16] midx: make some functions non-static Taylor Blau
2021-03-11 17:05   ` [PATCH v3 12/16] Documentation/technical: describe multi-pack reverse indexes Taylor Blau
2021-03-29 12:12     ` Jeff King
2021-03-29 21:22       ` Taylor Blau
2021-03-11 17:05   ` [PATCH v3 13/16] pack-revindex: read " Taylor Blau
2021-03-29 12:43     ` Jeff King
2021-03-29 21:27       ` Taylor Blau
2021-03-11 17:05   ` [PATCH v3 14/16] pack-write.c: extract 'write_rev_file_order' Taylor Blau
2021-03-11 17:05   ` [PATCH v3 15/16] pack-revindex: write multi-pack reverse indexes Taylor Blau
2021-03-29 12:53     ` Jeff King
2021-03-29 21:30       ` Taylor Blau
2021-03-11 17:05   ` [PATCH v3 16/16] midx.c: improve cache locality in midx_pack_order_cmp() Taylor Blau
2021-03-29 12:59     ` Jeff King
2021-03-29 21:34       ` Taylor Blau
2021-03-30  7:15         ` Jeff King
2021-03-12 15:16   ` [PATCH v3 00/16] midx: implement a multi-pack reverse index Derrick Stolee
2021-03-29 13:05   ` Jeff King
2021-03-29 21:30     ` Junio C Hamano
2021-03-29 21:37     ` Taylor Blau
2021-03-30  7:15       ` Jeff King
2021-03-30 13:37         ` Taylor Blau
2021-03-30 15:03 ` [PATCH v4 " Taylor Blau
2021-03-30 15:03   ` [PATCH v4 01/16] builtin/multi-pack-index.c: inline 'flags' with options Taylor Blau
2021-03-30 15:03   ` [PATCH v4 02/16] builtin/multi-pack-index.c: don't handle 'progress' separately Taylor Blau
2021-03-30 15:03   ` [PATCH v4 03/16] builtin/multi-pack-index.c: define common usage with a macro Taylor Blau
2021-03-30 15:03   ` [PATCH v4 04/16] builtin/multi-pack-index.c: split sub-commands Taylor Blau
2021-03-30 15:04   ` [PATCH v4 05/16] builtin/multi-pack-index.c: don't enter bogus cmd_mode Taylor Blau
2021-03-30 15:04   ` [PATCH v4 06/16] builtin/multi-pack-index.c: display usage on unrecognized command Taylor Blau
2021-03-30 15:04   ` [PATCH v4 07/16] t/helper/test-read-midx.c: add '--show-objects' Taylor Blau
2021-03-30 15:04   ` [PATCH v4 08/16] midx: allow marking a pack as preferred Taylor Blau
2021-04-01  0:32     ` Taylor Blau
2021-03-30 15:04   ` [PATCH v4 09/16] midx: don't free midx_name early Taylor Blau
2021-03-30 15:04   ` [PATCH v4 10/16] midx: keep track of the checksum Taylor Blau
2021-03-30 15:04   ` [PATCH v4 11/16] midx: make some functions non-static Taylor Blau
2021-03-30 15:04   ` [PATCH v4 12/16] Documentation/technical: describe multi-pack reverse indexes Taylor Blau
2021-03-30 15:04   ` [PATCH v4 13/16] pack-revindex: read " Taylor Blau
2021-03-30 15:04   ` [PATCH v4 14/16] pack-write.c: extract 'write_rev_file_order' Taylor Blau
2021-09-08  1:08     ` [PATCH] pack-write: skip *.rev work when not writing *.rev Ævar Arnfjörð Bjarmason
2021-09-08  1:35       ` Carlo Arenas
2021-09-08  2:42         ` Taylor Blau
2021-09-08 15:47           ` Junio C Hamano
2021-09-08  2:50       ` Taylor Blau [this message]
2021-09-08  3:50         ` Taylor Blau
2021-09-08 10:18           ` Ævar Arnfjörð Bjarmason
2021-09-08 16:32             ` Taylor Blau
2021-03-30 15:04   ` [PATCH v4 15/16] pack-revindex: write multi-pack reverse indexes Taylor Blau
2021-03-30 15:04   ` [PATCH v4 16/16] midx.c: improve cache locality in midx_pack_order_cmp() Taylor Blau
2021-03-30 15:45   ` [PATCH v4 00/16] midx: implement a multi-pack reverse index Jeff King
2021-03-30 15:49     ` Taylor Blau
2021-03-30 16:01       ` Jeff King

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