From: Jeff King <peff@peff.net>
To: Taylor Blau <me@ttaylorr.com>
Cc: git@vger.kernel.org, dstolee@microsoft.com, gitster@pobox.com,
jrnieder@gmail.com
Subject: Re: [PATCH v2 1/8] packfile: prepare for the existence of '*.rev' files
Date: Mon, 25 Jan 2021 13:27:00 -0500 [thread overview]
Message-ID: <YA8NdHJloTf15qXf@coredump.intra.peff.net> (raw)
In-Reply-To: <YA8DlQwSzNZXq+AU@nand.local>
On Mon, Jan 25, 2021 at 12:44:53PM -0500, Taylor Blau wrote:
> Thanks for including a compelling argument in favor of the approach that
> I took in this patch.
>
> I added something along the lines of what you suggested to the final
> paragraph, so now it concludes nicely instead of ending in a comma. I
> briefly considered whether I should add something about how these
> operations scale and how the warming efforts are really amortized across
> all of the objects, but I decided against it.
>
> I think that this argument is already documented here, and that there's
> no way to concisely state it in an already long patch. Interested
> readers will easily be able to find our discussion here, which is good.
That sounds good. It is sort of arguing against a strawman anyway.
> > It mostly looks good to me. I agree with Junio that "compute" is a
> > better verb than "load" for generating the in-memory revindex.
>
> Yeah, I settled on load_pack_revindex() either calling
> "create_pack_revindex_in_memory()" or "load_pack_revindex_from_disk()".
Perfect.
> > If p->revindex_data were "const uint32_t *", then this line would just
> > be:
> >
> > return get_be32(p->revindex_data + pos);
> >
> > Not a huge deal either way since the whole point is to abstract this
> > behind a function where it only has to be written once. I don't think
> > there is any downside from the compiler's view (and we already use this
> > trick for the bitmap name-hash cache).
>
> Honestly, I'm not a huge fan of implicitly scaling pos by
> sizeof(*p->revindex_data), but I can understand why it reads more
> clearly here. I don't really feel strongly either way, so I'm happy to
> change it in favor of your suggestion.
>
> Of course, since RIDX_HEADER_SIZE is in bytes, not uint32_t's (and it
> has to be, since it's also used in the RIDX_MIN_SIZE macro, which is
> compared against the st_size of stating the .rev file), you have to do
> gross stuff like:
>
> p->revindex_data = (const uint32_t *)((const char *)p->revindex_map + RIDX_HEADER_SIZE);
>
> But I guess the tradeoff is worth it, since the readers are easier to
> parse.
Yeah, that is definitely a downside. Perhaps keeping everything in bytes
makes things a bit more obvious. In which case I might suggest that
revindex_data just be a "const char *". You'd have to scale any pointer
computations at the point of use then, but you'd avoid needing to do any
extra casting.
-Peff
next prev parent reply other threads:[~2021-01-25 18:30 UTC|newest]
Thread overview: 82+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-08 18:19 [PATCH 0/8] pack-revindex: introduce on-disk '.rev' format Taylor Blau
2021-01-08 18:19 ` [PATCH 1/8] packfile: prepare for the existence of '*.rev' files Taylor Blau
2021-01-08 18:20 ` [PATCH 2/8] pack-write.c: prepare to write 'pack-*.rev' files Taylor Blau
2021-01-08 18:20 ` [PATCH 3/8] builtin/index-pack.c: write reverse indexes Taylor Blau
2021-01-08 18:20 ` [PATCH 4/8] builtin/pack-objects.c: respect 'pack.writeReverseIndex' Taylor Blau
2021-01-08 18:20 ` [PATCH 5/8] Documentation/config/pack.txt: advertise 'pack.writeReverseIndex' Taylor Blau
2021-01-08 18:20 ` [PATCH 6/8] t: prepare for GIT_TEST_WRITE_REV_INDEX Taylor Blau
2021-01-12 17:11 ` Ævar Arnfjörð Bjarmason
2021-01-12 18:40 ` Taylor Blau
2021-01-08 18:20 ` [PATCH 7/8] t: support GIT_TEST_WRITE_REV_INDEX Taylor Blau
2021-01-12 16:49 ` Derrick Stolee
2021-01-12 17:34 ` Taylor Blau
2021-01-12 17:18 ` Ævar Arnfjörð Bjarmason
2021-01-12 17:39 ` Derrick Stolee
2021-01-12 18:17 ` Taylor Blau
2021-01-08 18:20 ` [PATCH 8/8] pack-revindex: ensure that on-disk reverse indexes are given precedence Taylor Blau
2021-01-13 22:28 ` [PATCH v2 0/8] pack-revindex: introduce on-disk '.rev' format Taylor Blau
2021-01-13 22:28 ` [PATCH v2 1/8] packfile: prepare for the existence of '*.rev' files Taylor Blau
2021-01-14 7:22 ` Junio C Hamano
2021-01-14 12:07 ` Derrick Stolee
2021-01-14 19:57 ` Jeff King
2021-01-14 18:28 ` Taylor Blau
2021-01-14 7:26 ` Junio C Hamano
2021-01-14 18:13 ` Taylor Blau
2021-01-14 20:57 ` Junio C Hamano
2021-01-22 22:54 ` Jeff King
2021-01-25 17:44 ` Taylor Blau
2021-01-25 18:27 ` Jeff King [this message]
2021-01-25 19:04 ` Junio C Hamano
2021-01-25 19:23 ` Taylor Blau
2021-01-13 22:28 ` [PATCH v2 2/8] pack-write.c: prepare to write 'pack-*.rev' files Taylor Blau
2021-01-22 23:24 ` Jeff King
2021-01-25 19:15 ` Taylor Blau
2021-01-26 21:43 ` Jeff King
2021-01-13 22:28 ` [PATCH v2 3/8] builtin/index-pack.c: write reverse indexes Taylor Blau
2021-01-22 23:53 ` Jeff King
2021-01-25 20:03 ` Taylor Blau
2021-01-13 22:28 ` [PATCH v2 4/8] builtin/pack-objects.c: respect 'pack.writeReverseIndex' Taylor Blau
2021-01-22 23:57 ` Jeff King
2021-01-23 0:08 ` Jeff King
2021-01-25 20:21 ` Taylor Blau
2021-01-25 20:50 ` Jeff King
2021-01-13 22:28 ` [PATCH v2 5/8] Documentation/config/pack.txt: advertise 'pack.writeReverseIndex' Taylor Blau
2021-01-13 22:28 ` [PATCH v2 6/8] t: prepare for GIT_TEST_WRITE_REV_INDEX Taylor Blau
2021-01-13 22:28 ` [PATCH v2 7/8] t: support GIT_TEST_WRITE_REV_INDEX Taylor Blau
2021-01-13 22:28 ` [PATCH v2 8/8] pack-revindex: ensure that on-disk reverse indexes are given precedence Taylor Blau
2021-01-25 23:37 ` [PATCH v3 00/10] pack-revindex: introduce on-disk '.rev' format Taylor Blau
2021-01-25 23:37 ` [PATCH v3 01/10] packfile: prepare for the existence of '*.rev' files Taylor Blau
2021-01-29 0:27 ` Jeff King
2021-01-29 1:14 ` Taylor Blau
2021-01-30 8:39 ` Jeff King
2021-01-25 23:37 ` [PATCH v3 02/10] pack-write.c: prepare to write 'pack-*.rev' files Taylor Blau
2021-01-25 23:37 ` [PATCH v3 03/10] builtin/index-pack.c: allow stripping arbitrary extensions Taylor Blau
2021-01-29 0:28 ` Jeff King
2021-01-29 1:15 ` Taylor Blau
2021-01-25 23:37 ` [PATCH v3 04/10] builtin/index-pack.c: write reverse indexes Taylor Blau
2021-01-25 23:37 ` [PATCH v3 05/10] builtin/pack-objects.c: respect 'pack.writeReverseIndex' Taylor Blau
2021-01-25 23:37 ` [PATCH v3 06/10] Documentation/config/pack.txt: advertise 'pack.writeReverseIndex' Taylor Blau
2021-01-29 0:30 ` Jeff King
2021-01-29 1:17 ` Taylor Blau
2021-01-30 8:41 ` Jeff King
2021-01-25 23:37 ` [PATCH v3 07/10] t: prepare for GIT_TEST_WRITE_REV_INDEX Taylor Blau
2021-01-29 0:45 ` Jeff King
2021-01-29 1:09 ` Eric Sunshine
2021-01-29 1:21 ` Taylor Blau
2021-01-30 8:43 ` Jeff King
2021-01-29 2:42 ` Junio C Hamano
2021-01-25 23:37 ` [PATCH v3 08/10] t: support GIT_TEST_WRITE_REV_INDEX Taylor Blau
2021-01-29 0:47 ` Jeff King
2021-01-25 23:37 ` [PATCH v3 09/10] pack-revindex: ensure that on-disk reverse indexes are given precedence Taylor Blau
2021-01-29 0:53 ` Jeff King
2021-01-29 1:25 ` Taylor Blau
2021-01-30 8:46 ` Jeff King
2021-01-25 23:37 ` [PATCH v3 10/10] t5325: check both on-disk and in-memory reverse index Taylor Blau
2021-01-29 1:04 ` Jeff King
2021-01-29 1:05 ` Jeff King
2021-01-29 1:32 ` Taylor Blau
2021-01-30 8:47 ` Jeff King
2021-01-26 2:36 ` [PATCH v3 00/10] pack-revindex: introduce on-disk '.rev' format Junio C Hamano
2021-01-26 2:49 ` Taylor Blau
2021-01-29 1:06 ` Jeff King
2021-01-29 1:34 ` Taylor Blau
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