From: Derrick Stolee <stolee@gmail.com>
To: Junio C Hamano <gitster@pobox.com>
Cc: Victoria Dye via GitGitGadget <gitgitgadget@gmail.com>,
git@vger.kernel.org, Victoria Dye <vdye@github.com>
Subject: Re: [PATCH v3 2/3] sparse-index: add ensure_correct_sparsity function
Date: Wed, 27 Oct 2021 21:24:59 -0400 [thread overview]
Message-ID: <bc960863-7ff2-d6bf-9710-6803f3784751@gmail.com> (raw)
In-Reply-To: <xmqqbl3aupbh.fsf@gitster.g>
On 10/27/2021 5:32 PM, Junio C Hamano wrote:
> Derrick Stolee <stolee@gmail.com> writes:
>
>>> +int convert_to_sparse(struct index_state *istate, int flags)
>>> +{
>>> + /*
>>> + * If the index is already sparse, empty, or otherwise
>>> + * cannot be converted to sparse, do not convert.
>>> + */
>>> + if (istate->sparse_index || !istate->cache_nr ||
>>> + !is_sparse_index_allowed(istate, flags))
>>> + return 0;
>
> Shouldn't we also at least do this? Blindly blowing away the entire
> cache-tree and rebuilding it from scratch may be hiding a latent bug
> somewhere else, but is never supposed to be needed, and is a huge
> waste of computational resources.
>
> I say "at least" here, because a cache tree that is partially valid
> should be safely salvageable---at least that was the intention back
> when I designed the subsystem.
I think you are right, what you propose below. It certainly seems
like it would work, and even speed up the conversion from full to
sparse. I think I erred on the side of extreme caution and used
a hope that converting to sparse would be rare.
> sparse-index.c | 24 +++++++++++++-----------
> 1 file changed, 13 insertions(+), 11 deletions(-)
>
> diff --git c/sparse-index.c w/sparse-index.c
> index bc3ee358c6..a95c3386f3 100644
> --- c/sparse-index.c
> +++ w/sparse-index.c
> @@ -188,17 +188,19 @@ int convert_to_sparse(struct index_state *istate, int flags)
> if (index_has_unmerged_entries(istate))
> return 0;
>
> - /* Clear and recompute the cache-tree */
> - cache_tree_free(&istate->cache_tree);
> - /*
> - * Silently return if there is a problem with the cache tree update,
> - * which might just be due to a conflict state in some entry.
> - *
> - * This might create new tree objects, so be sure to use
> - * WRITE_TREE_MISSING_OK.
> - */
> - if (cache_tree_update(istate, WRITE_TREE_MISSING_OK))
> - return 0;
> + if (!cache_tree_fully_valid(&istate->cache_tree)) {
> + /* Clear and recompute the cache-tree */
> + cache_tree_free(&istate->cache_tree);
> + /*
> + * Silently return if there is a problem with the cache tree update,
> + * which might just be due to a conflict state in some entry.
> + *
> + * This might create new tree objects, so be sure to use
> + * WRITE_TREE_MISSING_OK.
> + */
> + if (cache_tree_update(istate, WRITE_TREE_MISSING_OK))
> + return 0;
> + }
I think at this point we have enough tests that check the sparse index
and its different conversion points that the test suite might catch if
this is a bad idea. Note that this is only a change of behavior if the
cache-tree is valid, which I expect to be the case most of the time in
the tests.
Thanks,
-Stolee
next prev parent reply other threads:[~2021-10-28 1:25 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
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 [this message]
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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