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From: Derrick Stolee <stolee@gmail.com>
To: Elijah Newren <newren@gmail.com>,
	Derrick Stolee via GitGitGadget <gitgitgadget@gmail.com>
Cc: Git Mailing List <git@vger.kernel.org>, Jeff King <peff@peff.net>,
	Taylor Blau <me@ttaylorr.com>,
	Jonathan Nieder <jrnieder@gmail.com>,
	Derrick Stolee <dstolee@microsoft.com>
Subject: Re: [PATCH 06/10] sparse-checkout: use oidset to prevent repeat blobs
Date: Thu, 21 May 2020 13:54:36 -0400	[thread overview]
Message-ID: <b78b124a-81f2-933a-775d-1d8256e83e05@gmail.com> (raw)
In-Reply-To: <CABPp-BGcjpJOht7ip_cPcHEtd3kx5fCwm=i19narWCEfCUwWAQ@mail.gmail.com>

On 5/20/2020 11:49 PM, Elijah Newren wrote:
> Replying to my own questions...
> 
> On Wed, May 20, 2020 at 9:40 AM Elijah Newren <newren@gmail.com> wrote:
>>
>> On Thu, May 7, 2020 at 6:21 AM Derrick Stolee via GitGitGadget
>> <gitgitgadget@gmail.com> wrote:
>>>
>>> From: Derrick Stolee <dstolee@microsoft.com>
>>>
>>> As we parse the in-tree config files that store the sparse.dir values
>>> used to create an in-tree sparse-checkout definition, we can easily
>>> avoid parsing the same file multiple times by using an oidset on those
>>> blobs. We only parse if the oid is new to the oidset.
>>>
>>> This is unlikely to have a major performance benefit right now, but will
>>> be extremely important when we introduce the sparse.inherit options to
>>> link multiple files in a directed graph. This oidset will prevent
>>> infinite loops when cycles exist in that digraph, or exponential blowups
>>> even in the case of a directed acyclic graph.
>>
>> I'm still not sure if I like the idea of having a mirror dependency
>> structure separate from (and duplicative of) the build code; I'm still
>> mulling that over.
> 
> I mentioned this to a few other buildsystem folks at $DAYJOB.  They
> were strongly opposed to having more than one source of truth, but
> generating the git in-tree sparse values from the official build
> system files, with commit hooks and build system checks to make sure
> they get updated seemed like it'd be fine or not concern them much.

The intention is that these files are "downstream" from the build
system. As the build changes, it would adjust the config files to
tell Git what to do.

>> It's good that you've protected against infinite loops.
>>
>> Is there any reason to prefer swallowing infinite loops rather than
>> warning or flagging as an error?  (I'm not sure, just thinking my
>> questions out loud.)
> 
> The buildsystem folks also reminded me that we have cylic dependencies
> already, and although it's absolutely ugly, it is somewhat forced on
> us by a combination of different external tools that we can't change.
> As such, warnings or errors would be really annoying and we'd be one
> of the ones to want to turn them off.  So drop that idea from me.  :-)

This is more common than one might think!

Thanks for taking a look,
-Stolee

  reply	other threads:[~2020-05-21 17:54 UTC|newest]

Thread overview: 32+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-05-07 13:17 [PATCH 00/10] [RFC] In-tree sparse-checkout definitions Derrick Stolee via GitGitGadget
2020-05-07 13:17 ` [PATCH 01/10] unpack-trees: avoid array out-of-bounds error Derrick Stolee via GitGitGadget
2020-05-07 22:27   ` Junio C Hamano
2020-05-08 12:19     ` Derrick Stolee
2020-05-08 15:09       ` Junio C Hamano
2020-05-20 16:32     ` Elijah Newren
2020-05-07 13:17 ` [PATCH 02/10] sparse-checkout: move code from builtin Derrick Stolee via GitGitGadget
2020-05-07 13:17 ` [PATCH 03/10] sparse-checkout: move code from unpack-trees.c Derrick Stolee via GitGitGadget
2020-05-07 13:17 ` [PATCH 04/10] sparse-checkout: allow in-tree definitions Derrick Stolee via GitGitGadget
2020-05-07 22:58   ` Junio C Hamano
2020-05-08 15:40     ` Derrick Stolee
2020-05-20 17:52       ` Elijah Newren
2020-06-17 23:07         ` Elijah Newren
2020-06-18  8:18           ` Son Luong Ngoc
2020-05-07 13:17 ` [PATCH 05/10] sparse-checkout: automatically update in-tree definition Derrick Stolee via GitGitGadget
2020-05-20 16:28   ` Elijah Newren
2020-05-07 13:17 ` [PATCH 06/10] sparse-checkout: use oidset to prevent repeat blobs Derrick Stolee via GitGitGadget
2020-05-20 16:40   ` Elijah Newren
2020-05-21  3:49     ` Elijah Newren
2020-05-21 17:54       ` Derrick Stolee [this message]
2020-05-07 13:17 ` [PATCH 07/10] sparse-checkout: define in-tree dependencies Derrick Stolee via GitGitGadget
2020-05-20 18:10   ` Elijah Newren
2020-05-30 17:26     ` Elijah Newren
2020-05-07 13:17 ` [PATCH 08/10] Makefile: skip git-gui if dir is missing Derrick Stolee via GitGitGadget
2020-05-07 13:17 ` [PATCH 09/10] Makefile: disable GETTEXT when 'po' " Derrick Stolee via GitGitGadget
2020-05-07 13:17 ` [PATCH 10/10] .sparse: add in-tree sparse-checkout for Git Derrick Stolee via GitGitGadget
2020-05-20 17:38 ` [PATCH 00/10] [RFC] In-tree sparse-checkout definitions Elijah Newren
2020-06-17 23:14 ` Elijah Newren
2020-06-18  1:42   ` Derrick Stolee
2020-06-18  1:59     ` Elijah Newren
2020-06-18  3:01       ` Derrick Stolee
2020-06-18  5:03         ` Elijah Newren

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