From: Junio C Hamano <gitster@pobox.com>
To: "Victoria Dye via GitGitGadget" <gitgitgadget@gmail.com>
Cc: git@vger.kernel.org, stolee@gmail.com, Victoria Dye <vdye@github.com>
Subject: Re: [PATCH 2/2] sparse-index: update index read to consider index.sparse config
Date: Fri, 15 Oct 2021 14:53:41 -0700 [thread overview]
Message-ID: <xmqqh7di3qfu.fsf@gitster.g> (raw)
In-Reply-To: <c6279b225454af0cf3b54586127eb91206593af3.1634327697.git.gitgitgadget@gmail.com> (Victoria Dye via GitGitGadget's message of "Fri, 15 Oct 2021 19:54:57 +0000")
"Victoria Dye via GitGitGadget" <gitgitgadget@gmail.com> writes:
> From: Victoria Dye <vdye@github.com>
>
> Use the index.sparse config setting to expand or collapse the index when
> read. Previously, index.sparse would determine how the index would be
> written to disk, but would not enforce whether the index is read into memory
> as full or sparse. Now, the index is expanded when a sparse index is read
> with `index.sparse=false` and is collapsed to sparse when a full index is
> read with `index.sparse=true` (and the command does not require a full
> index).
Instead of calling both in-core index and on-disk index, perhaps use
"the in-core index" as appropriately in the above description and
the result would become much less ambigous.
My knee-jerk reaction was that it is of dubious value to spend
cycles to make the in-core index sparse after reading a non-sparse
index from the disk to give to the caller, but this hurts only the
commands that are not yet sparse-aware and call ensure_full_index()
as the first thing they do. To them, we are wasting cycles to
shrink and expand for no good reason, and after they are done, the
final writeout would create a sparse on-disk index.
Besides, the on-disk index is expected to be sparse most of the time
when index.sparse is true, so it is hopefully a one-time waste that
corrects by itself.
For all commands that are sparse-aware, especially when asked to
perform their operation on the paths that are not hidden by a
tree-like index entry, it may or may not be a win, but the downside
would be much smaller. The cost to shrink a full in-core index
before writing out as a sparse one should be comparable to the cost
to shrink a full in-core index just read from the disk before the
sparse-index-aware caller works on it and leaves a still mostly
sparse in-core index to be written out without much extra work to
re-shrink it to the disk.
> This makes the behavior of `index.sparse` more intuitive, as it now clearly
> enables/disables usage of a sparse index.
It is a minor thing, so I am willing to let it pass, but I am not
sure about this claim. The write-out codepath ensures, independent
of this change, that a full on-disk index is corrected to become
sparse when the configuration is set to true, and a sparse on-disk
index is corrected to become full when the configuration is set to
false, no?
So the only "intuitive"-ness we may be gaining is that the codepaths
that are sparse-aware would work in their "sparse" (non-"sparse")
mode when index.sparse is set to true (false), respectively, no
matter how sparse (or not sparse) the on-disk index they work on is
initially. That might help debuggability (assuming that converting
between the full and sparse forms are working correctly), but I am
not sure if that is something end users would even care about.
> - if (istate->repo->settings.command_requires_full_index)
> + if (!istate->repo->settings.sparse_index ||
> + istate->repo->settings.command_requires_full_index)
> ensure_full_index(istate);
> + else if (!istate->sparse_index)
> + convert_to_sparse(istate, 0);
>
> return istate->cache_nr;
Quite straight-forward. Looking good.
next prev parent reply other threads:[~2021-10-15 21:53 UTC|newest]
Thread overview: 44+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-10-15 19:54 [PATCH 0/2] sparse-index: expand/collapse based on 'index.sparse' Victoria Dye via GitGitGadget
2021-10-15 19:54 ` [PATCH 1/2] test-read-cache.c: prepare_repo_settings after config init Victoria Dye via GitGitGadget
2021-10-15 19:54 ` [PATCH 2/2] sparse-index: update index read to consider index.sparse config Victoria Dye via GitGitGadget
2021-10-15 21:53 ` Junio C Hamano [this message]
2021-10-17 1:21 ` Derrick Stolee
2021-10-17 5:58 ` Junio C Hamano
2021-10-17 19:33 ` Derrick Stolee
2021-10-18 1:15 ` Junio C Hamano
2021-10-18 13:25 ` Derrick Stolee
2021-10-18 14:14 ` Victoria Dye
2021-10-21 13:26 ` Derrick Stolee
2021-10-18 16:09 ` Junio C Hamano
2021-10-21 20:48 ` [PATCH v2 0/3] sparse-index: expand/collapse based on 'index.sparse' Victoria Dye via GitGitGadget
2021-10-21 20:48 ` [PATCH v2 1/3] test-read-cache.c: prepare_repo_settings after config init Victoria Dye via GitGitGadget
2021-10-21 20:48 ` [PATCH v2 2/3] sparse-index: add ensure_correct_sparsity function Victoria Dye via GitGitGadget
2021-10-21 22:20 ` Junio C Hamano
2021-10-27 17:21 ` Victoria Dye
2021-10-21 20:48 ` [PATCH v2 3/3] sparse-index: update do_read_index to ensure correct sparsity Victoria Dye via GitGitGadget
2021-10-27 18:20 ` [PATCH v3 0/3] sparse-index: expand/collapse based on 'index.sparse' Victoria Dye via GitGitGadget
2021-10-27 18:20 ` [PATCH v3 1/3] test-read-cache.c: prepare_repo_settings after config init Victoria Dye via GitGitGadget
2021-10-27 18:20 ` [PATCH v3 2/3] sparse-index: add ensure_correct_sparsity function Victoria Dye via GitGitGadget
2021-10-27 20:07 ` Derrick Stolee
2021-10-27 21:32 ` Junio C Hamano
2021-10-28 1:24 ` Derrick Stolee
2021-10-29 13:43 ` Victoria Dye
2021-10-27 18:20 ` [PATCH v3 3/3] sparse-index: update do_read_index to ensure correct sparsity Victoria Dye via GitGitGadget
2021-10-27 20:08 ` [PATCH v3 0/3] sparse-index: expand/collapse based on 'index.sparse' Derrick Stolee
2021-10-29 13:51 ` [PATCH v4 0/4] " Victoria Dye via GitGitGadget
2021-10-29 13:51 ` [PATCH v4 1/4] test-read-cache.c: prepare_repo_settings after config init Victoria Dye via GitGitGadget
2021-10-29 13:51 ` [PATCH v4 2/4] sparse-index: avoid unnecessary cache tree clearing Victoria Dye via GitGitGadget
2021-10-29 18:45 ` Junio C Hamano
2021-10-29 19:00 ` Derrick Stolee
2021-10-29 20:01 ` Junio C Hamano
2021-10-29 13:51 ` [PATCH v4 3/4] sparse-index: add ensure_correct_sparsity function Victoria Dye via GitGitGadget
2021-10-29 13:51 ` [PATCH v4 4/4] sparse-index: update do_read_index to ensure correct sparsity Victoria Dye via GitGitGadget
2021-11-22 17:36 ` Elijah Newren
2021-11-22 18:59 ` Victoria Dye
2021-11-22 17:40 ` [PATCH v4 0/4] sparse-index: expand/collapse based on 'index.sparse' Elijah Newren
2021-11-23 0:20 ` [PATCH v5 " Victoria Dye via GitGitGadget
2021-11-23 0:20 ` [PATCH v5 1/4] test-read-cache.c: prepare_repo_settings after config init Victoria Dye via GitGitGadget
2021-11-23 0:20 ` [PATCH v5 2/4] sparse-index: avoid unnecessary cache tree clearing Victoria Dye via GitGitGadget
2021-11-23 0:20 ` [PATCH v5 3/4] sparse-index: add ensure_correct_sparsity function Victoria Dye via GitGitGadget
2021-11-23 0:20 ` [PATCH v5 4/4] sparse-index: update do_read_index to ensure correct sparsity Victoria Dye via GitGitGadget
2021-11-23 17:21 ` [PATCH v5 0/4] sparse-index: expand/collapse based on 'index.sparse' Elijah Newren
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