git@vger.kernel.org list mirror (unofficial, one of many)
 help / color / mirror / code / Atom feed
From: Son Luong Ngoc <sluongng@gmail.com>
To: Derrick Stolee via GitGitGadget <gitgitgadget@gmail.com>
Cc: git <git@vger.kernel.org>,
	sandals@crustytoothpaste.net, steadmon@google.com,
	jrnieder@gmail.com, Jeff King <peff@peff.net>,
	congdanhqx@gmail.com, phillip.wood123@gmail.com,
	Emily Shaffer <emilyshaffer@google.com>,
	Jonathan Tan <jonathantanmy@google.com>,
	Derrick Stolee <derrickstolee@github.com>,
	Derrick Stolee <dstolee@microsoft.com>
Subject: Re: [PATCH 8/9] maintenance: auto-size incremental-repack batch
Date: Thu, 6 Aug 2020 19:02:30 +0200	[thread overview]
Message-ID: <6FA8F54A-C92D-497B-895F-AC6E8287AACD@gmail.com> (raw)
In-Reply-To: <c3487fb8e3e72949080f51f341655f37b5f2f03f.1596731425.git.gitgitgadget@gmail.com>

Hi Derrick,

> On Aug 6, 2020, at 18:30, Derrick Stolee via GitGitGadget <gitgitgadget@gmail.com> wrote:
> 
> From: Derrick Stolee <dstolee@microsoft.com>
> 
> When repacking during the 'incremental-repack' task, we use the
> --batch-size option in 'git multi-pack-index repack'. The initial setting
> used --batch-size=0 to repack everything into a single pack-file. This is
> not sustainable for a large repository. The amount of work required is
> also likely to use too many system resources for a background job.
> 
> Update the 'incremental-repack' task by dynamically computing a
> --batch-size option based on the current pack-file structure.
> 
> The dynamic default size is computed with this idea in mind for a client
> repository that was cloned from a very large remote: there is likely one
> "big" pack-file that was created at clone time. Thus, do not try
> repacking it as it is likely packed efficiently by the server.
> 
> Instead, we select the second-largest pack-file, and create a batch size
> that is one larger than that pack-file. If there are three or more
> pack-files, then this guarantees that at least two will be combined into
> a new pack-file.

I have been using this strategy with git-care.sh [1] with large success.
However it worth to note that there are still edge case where I observed that
pack count keep increasing because using '--batch-size=<second-biggest-pack>+1'
did not resulted in any repacking.
In one case, I have observed a local copy went up to 160+ packs without being able
to repack.

I have been considering whether a strategy such as falling back to the '(3rd biggest
pack size) + 1' and 4th and 5th and so on... when midx repack call resulted in no-op,
as that was how I fixed my repo when the edge case happen.

Such strategy would require a way to detect midx repack to signal when no-op happen,
so something like 'git multi-pack-index repack --batch-size=123456 --exit-code' would
be much desirable.

> 
> Of course, this means that the second-largest pack-file size is likely
> to grow over time and may eventually surpass the initially-cloned
> pack-file. Recall that the pack-file batch is selected in a greedy
> manner: the packs are considered from oldest to newest and are selected
> if they have size smaller than the batch size until the total selected
> size is larger than the batch size. Thus, that oldest "clone" pack will
> be first to repack after the new data creates a pack larger than that.
> 
> We also want to place some limits on how large these pack-files become,
> in order to bound the amount of time spent repacking. A maximum
> batch-size of two gigabytes means that large repositories will never be
> packed into a single pack-file using this job, but also that repack is
> rather expensive. This is a trade-off that is valuable to have if the
> maintenance is being run automatically or in the background. Users who
> truly want to optimize for space and performance (and are willing to pay
> the upfront cost of a full repack) can use the 'gc' task to do so.
> 
> Create a test for this two gigabyte limit by creating an EXPENSIVE test
> that generates two pack-files of roughly 2.5 gigabytes in size, then
> performs an incremental repack. Check that the --batch-size argument in
> the subcommand uses the hard-coded maximum.
> 
> Helped-by: Chris Torek <chris.torek@gmail.com>
> Reported-by: Son Luong Ngoc <sluongng@gmail.com>
> Signed-off-by: Derrick Stolee <dstolee@microsoft.com>

Generally, I have found working with '--batch-size' to be a bit unpredictable.
I wonder if we could tweak the behavior somewhat so that its more consistent
to use and test?

Thanks a lot for making this happen.
Hope this patch would make it in stable soon

Cheers,
Son Luong.

[1]: https://github.com/sluongng/git-care

  reply	other threads:[~2020-08-06 17:09 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 [this message]
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
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

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

  List information: http://vger.kernel.org/majordomo-info.html

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=6FA8F54A-C92D-497B-895F-AC6E8287AACD@gmail.com \
    --to=sluongng@gmail.com \
    --cc=congdanhqx@gmail.com \
    --cc=derrickstolee@github.com \
    --cc=dstolee@microsoft.com \
    --cc=emilyshaffer@google.com \
    --cc=git@vger.kernel.org \
    --cc=gitgitgadget@gmail.com \
    --cc=jonathantanmy@google.com \
    --cc=jrnieder@gmail.com \
    --cc=peff@peff.net \
    --cc=phillip.wood123@gmail.com \
    --cc=sandals@crustytoothpaste.net \
    --cc=steadmon@google.com \
    --subject='Re: [PATCH 8/9] maintenance: auto-size incremental-repack batch' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

Code repositories for project(s) associated with this inbox:

	https://80x24.org/mirrors/git.git

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).