From: Derrick Stolee <stolee@gmail.com>
To: Jonathan Tan <jonathantanmy@google.com>, gitgitgadget@gmail.com
Cc: git@vger.kernel.org, sandals@crustytoothpaste.net,
steadmon@google.com, jrnieder@gmail.com, peff@peff.net,
congdanhqx@gmail.com, phillip.wood123@gmail.com,
emilyshaffer@google.com, sluongng@gmail.com,
derrickstolee@github.com, dstolee@microsoft.com
Subject: Re: [PATCH v3 2/8] maintenance: add loose-objects task
Date: Thu, 24 Sep 2020 09:45:22 -0400 [thread overview]
Message-ID: <446e805a-6b83-a6b7-18a3-f99ac85a6fe1@gmail.com> (raw)
In-Reply-To: <20200922230937.906065-1-jonathantanmy@google.com>
On 9/22/2020 7:09 PM, Jonathan Tan wrote:
>> Create a 'loose-objects' task for the 'git maintenance run' command.
>> This helps clean up loose objects without disrupting concurrent Git
>> commands using the following sequence of events:
>>
>> 1. Run 'git prune-packed' to delete any loose objects that exist
>> in a pack-file. Concurrent commands will prefer the packed
>> version of the object to the loose version. (Of course, there
>> are exceptions for commands that specifically care about the
>> location of an object. These are rare for a user to run on
>> purpose, and we hope a user that has selected background
>> maintenance will not be trying to do foreground maintenance.)
>>
>> 2. Run 'git pack-objects' on a batch of loose objects. These
>> objects are grouped by scanning the loose object directories in
>> lexicographic order until listing all loose objects -or-
>> reaching 50,000 objects. This is more than enough if the loose
>> objects are created only by a user doing normal development.
>> We noticed users with _millions_ of loose objects because VFS
>> for Git downloads blobs on-demand when a file read operation
>> requires populating a virtual file.
>
> [snip]
>
>> This has potential of
>> happening in partial clones if someone runs 'git grep' or
>> otherwise evades the batch-download feature for requesting
>> promisor objects.
>
> This part is not strictly true, as even when Git lazy-fetches one
> object, it fetches it in the form of a packfile - so maybe remove this
> sentence.
This is a good point. I just did some testing and we do store these
single-object downloads as pack-files. My misunderstanding is due to
my own bias and experience with the GVFS protocol.
I have also heard that "git fetch" might explode some small pack-files
into loose objects, and I guess I expected the same here. However, that
is not the case for partial clone. I'll remove this.
> This is nevertheless a good feature to have - loose objects may not be
> created during lazy fetches, but they definitely are created during
> normal operation (e.g. commits). Git, as a whole, prefers packfiles over
> loose objects, and just packing the loose objects themselves instead of
> running repack (which goes through all reachable objects) is definitely
> better for large repositories.
Thanks,
-Stolee
next prev parent reply other threads:[~2020-09-24 13:45 UTC|newest]
Thread overview: 66+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-08-06 16:30 [PATCH 0/9] Maintenance II: prefetch, loose-objects, incremental-repack tasks Derrick Stolee via GitGitGadget
2020-08-06 16:30 ` [PATCH 1/9] fetch: optionally allow disabling FETCH_HEAD update Junio C Hamano via GitGitGadget
2020-08-12 23:10 ` Emily Shaffer
2020-08-13 0:03 ` Junio C Hamano
2020-08-13 1:45 ` Jonathan Nieder
2020-08-13 4:37 ` [PATCH v3] " Junio C Hamano
2020-08-14 1:13 ` Derrick Stolee
2020-08-14 1:32 ` Junio C Hamano
2020-08-06 16:30 ` [PATCH 2/9] maintenance: add prefetch task Derrick Stolee via GitGitGadget
2020-08-12 23:10 ` Emily Shaffer
2020-08-14 1:28 ` Derrick Stolee
2020-08-06 16:30 ` [PATCH 3/9] maintenance: add loose-objects task Derrick Stolee via GitGitGadget
2020-08-12 23:10 ` Emily Shaffer
2020-08-14 1:46 ` Derrick Stolee
2020-08-06 16:30 ` [PATCH 4/9] maintenance: create auto condition for loose-objects Derrick Stolee via GitGitGadget
2020-08-06 16:30 ` [PATCH 5/9] midx: enable core.multiPackIndex by default Derrick Stolee via GitGitGadget
2020-08-06 16:30 ` [PATCH 6/9] midx: use start_delayed_progress() Derrick Stolee via GitGitGadget
2020-08-06 16:30 ` [PATCH 7/9] maintenance: add incremental-repack task Derrick Stolee via GitGitGadget
2020-08-06 16:30 ` [PATCH 8/9] maintenance: auto-size incremental-repack batch Derrick Stolee via GitGitGadget
2020-08-06 17:02 ` Son Luong Ngoc
2020-08-06 18:13 ` Derrick Stolee
2020-08-06 16:30 ` [PATCH 9/9] maintenance: add incremental-repack auto condition Derrick Stolee via GitGitGadget
2020-08-18 14:25 ` [PATCH v2 0/9] Maintenance II: prefetch, loose-objects, incremental-repack tasks Derrick Stolee via GitGitGadget
2020-08-18 14:25 ` [PATCH v2 1/9] fetch: optionally allow disabling FETCH_HEAD update Junio C Hamano via GitGitGadget
2020-08-18 14:25 ` [PATCH v2 2/9] maintenance: add prefetch task Derrick Stolee via GitGitGadget
2020-08-18 14:25 ` [PATCH v2 3/9] maintenance: add loose-objects task Derrick Stolee via GitGitGadget
2020-08-18 14:25 ` [PATCH v2 4/9] maintenance: create auto condition for loose-objects Derrick Stolee via GitGitGadget
2020-08-18 14:25 ` [PATCH v2 5/9] midx: enable core.multiPackIndex by default Derrick Stolee via GitGitGadget
2020-08-18 14:25 ` [PATCH v2 6/9] midx: use start_delayed_progress() Derrick Stolee via GitGitGadget
2020-08-18 14:25 ` [PATCH v2 7/9] maintenance: add incremental-repack task Derrick Stolee via GitGitGadget
2020-08-18 14:25 ` [PATCH v2 8/9] maintenance: auto-size incremental-repack batch Derrick Stolee via GitGitGadget
2020-08-18 14:25 ` [PATCH v2 9/9] maintenance: add incremental-repack auto condition Derrick Stolee via GitGitGadget
2020-08-25 18:36 ` [PATCH v3 0/8] Maintenance II: prefetch, loose-objects, incremental-repack tasks Derrick Stolee via GitGitGadget
2020-08-25 18:36 ` [PATCH v3 1/8] maintenance: add prefetch task Derrick Stolee via GitGitGadget
2020-09-22 23:05 ` Jonathan Tan
2020-08-25 18:36 ` [PATCH v3 2/8] maintenance: add loose-objects task Derrick Stolee via GitGitGadget
2020-09-22 23:09 ` Jonathan Tan
2020-09-24 13:45 ` Derrick Stolee [this message]
2020-08-25 18:36 ` [PATCH v3 3/8] maintenance: create auto condition for loose-objects Derrick Stolee via GitGitGadget
2020-09-22 23:15 ` Jonathan Tan
2020-09-24 13:51 ` Derrick Stolee
2020-08-25 18:36 ` [PATCH v3 4/8] midx: enable core.multiPackIndex by default Derrick Stolee via GitGitGadget
2020-09-22 23:16 ` Jonathan Tan
2020-09-24 13:53 ` Derrick Stolee
2020-08-25 18:36 ` [PATCH v3 5/8] midx: use start_delayed_progress() Derrick Stolee via GitGitGadget
2020-08-25 18:36 ` [PATCH v3 6/8] maintenance: add incremental-repack task Derrick Stolee via GitGitGadget
2020-09-22 23:26 ` Jonathan Tan
2020-09-24 14:05 ` Derrick Stolee
2020-09-24 22:01 ` Jonathan Tan
2020-08-25 18:36 ` [PATCH v3 7/8] maintenance: auto-size incremental-repack batch Derrick Stolee via GitGitGadget
2020-08-25 18:36 ` [PATCH v3 8/8] maintenance: add incremental-repack auto condition Derrick Stolee via GitGitGadget
2020-09-22 23:52 ` Jonathan Tan
2020-08-25 20:59 ` [PATCH v3 0/8] Maintenance II: prefetch, loose-objects, incremental-repack tasks Junio C Hamano
2020-08-26 15:15 ` Son Luong Ngoc
2020-08-26 16:21 ` Derrick Stolee
2020-09-25 12:33 ` [PATCH v4 " Derrick Stolee via GitGitGadget
2020-09-25 12:33 ` [PATCH v4 1/8] maintenance: add prefetch task Derrick Stolee via GitGitGadget
2020-09-25 12:33 ` [PATCH v4 2/8] maintenance: add loose-objects task Derrick Stolee via GitGitGadget
2020-09-25 12:33 ` [PATCH v4 3/8] maintenance: create auto condition for loose-objects Derrick Stolee via GitGitGadget
2020-09-25 18:00 ` Junio C Hamano
2020-09-25 18:43 ` Derrick Stolee
2020-09-25 12:33 ` [PATCH v4 4/8] midx: enable core.multiPackIndex by default Derrick Stolee via GitGitGadget
2020-09-25 12:33 ` [PATCH v4 5/8] midx: use start_delayed_progress() Derrick Stolee via GitGitGadget
2020-09-25 12:33 ` [PATCH v4 6/8] maintenance: add incremental-repack task Derrick Stolee via GitGitGadget
2020-09-25 12:33 ` [PATCH v4 7/8] maintenance: auto-size incremental-repack batch Derrick Stolee via GitGitGadget
2020-09-25 12:33 ` [PATCH v4 8/8] maintenance: add incremental-repack auto condition Derrick Stolee via GitGitGadget
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