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From: Junio C Hamano <gitster@pobox.com>
To: Jonathan Tan <jonathantanmy@google.com>
Cc: git@vger.kernel.org, peff@peff.net
Subject: Re: [RFC PATCH 1/7] fetch-pack: allow NULL negotiator->add_tip
Date: Wed, 05 Aug 2020 12:53:21 -0700	[thread overview]
Message-ID: <xmqqo8noooni.fsf@gitster.c.googlers.com> (raw)
In-Reply-To: <044a782863dd690ed4e430b3793538f701a850c6.1596590295.git.jonathantanmy@google.com> (Jonathan Tan's message of "Tue, 4 Aug 2020 18:20:44 -0700")

Jonathan Tan <jonathantanmy@google.com> writes:

> In a subsequent patch, a null fetch negotiator will be introduced. This
> negotiator, among other things, will not need any tip information and
> will have a NULL add_tip.

After reading the original code that the patch touches, I know what
"a NULL add_tip" is, but it would have been nicer to readers if you
said "callback" or "method" or "function".

With or without the "if add_tip method is set to NULL, return
without doing anything" optimization, it does make sense to refactor
two existing places that do identical things.  

If all the current negotiators never have NULL in the .add_tip
field, however, I'd suspect that it would make it easier to
understand if this step is explained as refactoring duplicated code
into a single helper _without_ the early-return for optimization,
and then the step that introduces the negotiator that does want to
lack add_tip method to add the early return.  After all, if the null
negotiator added a pointer to a no-op function to its .add_tip field,
things would still work correctly without the early-return in the
new helper function, no?

> Teach fetch-pack to allow this, and to take advantage of this by
> avoiding a ref and alternate traversal when it can. To do this, this
> patch combines all invocations of functions that invoke add_tip into one
> function, and that function first checks whether add_tip is NULL.
>
> Signed-off-by: Jonathan Tan <jonathantanmy@google.com>
> ---
>  fetch-pack.c | 20 +++++++++++++-------
>  1 file changed, 13 insertions(+), 7 deletions(-)



>
> diff --git a/fetch-pack.c b/fetch-pack.c
> index 80fb3bd899..6c786f5970 100644
> --- a/fetch-pack.c
> +++ b/fetch-pack.c
> @@ -240,6 +240,16 @@ static void mark_tips(struct fetch_negotiator *negotiator,
>  	return;
>  }
>  
> +static void add_tips_and_alternates(struct fetch_negotiator *negotiator,
> +				    const struct oid_array *negotiation_tips)
> +{
> +	if (!negotiator->add_tip)
> +		return;
> +
> +	mark_tips(negotiator, negotiation_tips);
> +	for_each_cached_alternate(negotiator, insert_one_alternate_object);
> +}
> +
>  static int find_common(struct fetch_negotiator *negotiator,
>  		       struct fetch_pack_args *args,
>  		       int fd[2], struct object_id *result_oid,
> @@ -262,10 +272,8 @@ static int find_common(struct fetch_negotiator *negotiator,
>  			   PACKET_READ_CHOMP_NEWLINE |
>  			   PACKET_READ_DIE_ON_ERR_PACKET);
>  
> -	if (!args->no_dependents) {
> -		mark_tips(negotiator, args->negotiation_tips);
> -		for_each_cached_alternate(negotiator, insert_one_alternate_object);
> -	}
> +	if (!args->no_dependents)
> +		add_tips_and_alternates(negotiator, args->negotiation_tips);
>  
>  	fetching = 0;
>  	for ( ; refs ; refs = refs->next) {
> @@ -1575,9 +1583,7 @@ static struct ref *do_fetch_pack_v2(struct fetch_pack_args *args,
>  				else
>  					state = FETCH_SEND_REQUEST;
>  
> -				mark_tips(negotiator, args->negotiation_tips);
> -				for_each_cached_alternate(negotiator,
> -							  insert_one_alternate_object);
> +				add_tips_and_alternates(negotiator, args->negotiation_tips);
>  			} else {
>  				filter_refs(args, &ref, sought, nr_sought);
>  				state = FETCH_SEND_REQUEST;

  reply	other threads:[~2020-08-05 19:53 UTC|newest]

Thread overview: 57+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-07-24 22:38 [RFC PATCH] Modify fetch-pack to no longer die on error? Jonathan Tan
2020-07-24 23:07 ` Junio C Hamano
2020-07-24 23:11 ` Junio C Hamano
2020-07-25 21:41   ` Jeff King
2020-07-25 23:01     ` Junio C Hamano
2020-07-27 17:11       ` Jeff King
2020-07-28 19:23       ` Jonathan Tan
2020-07-28 20:08         ` Jeff King
2020-07-29 18:53           ` Jonathan Tan
2020-07-29 19:29             ` Jeff King
2020-07-29 19:02           ` Junio C Hamano
2020-07-29 22:55             ` Jonathan Tan
2020-08-05  1:20 ` [RFC PATCH 0/7] Lazy fetch with subprocess Jonathan Tan
2020-08-05  1:20   ` [RFC PATCH 1/7] fetch-pack: allow NULL negotiator->add_tip Jonathan Tan
2020-08-05 19:53     ` Junio C Hamano [this message]
2020-08-07 20:53       ` Jonathan Tan
2020-08-05  1:20   ` [RFC PATCH 2/7] fetch-pack: allow NULL negotiator->known_common Jonathan Tan
2020-08-05 20:08     ` Junio C Hamano
2020-08-05 22:11       ` Junio C Hamano
2020-08-07 20:59         ` Jonathan Tan
2020-08-05  1:20   ` [RFC PATCH 3/7] negotiator/null: add null fetch negotiator Jonathan Tan
2020-08-05  1:20   ` [RFC PATCH 4/7] fetch: --stdin Jonathan Tan
2020-08-05 20:33     ` Junio C Hamano
2020-08-07 21:10       ` Jonathan Tan
2020-08-07 21:58         ` Junio C Hamano
2020-08-07 21:10       ` Jonathan Tan
2020-08-05  1:20   ` [RFC PATCH 5/7] fetch: submodule config Jonathan Tan
2020-08-05  1:20   ` [RFC PATCH 6/7] fetch: only populate existing_refs if needed Jonathan Tan
2020-08-05  1:20   ` [RFC PATCH 7/7] promisor-remote: use subprocess to fetch Jonathan Tan
2020-08-11 22:52 ` [PATCH v2 0/7] Lazy fetch with subprocess Jonathan Tan
2020-08-11 22:52   ` [PATCH v2 1/7] negotiator/null: add null fetch negotiator Jonathan Tan
2020-08-12 12:55     ` Derrick Stolee
2020-08-12 16:44       ` Junio C Hamano
2020-08-12 17:29         ` Jonathan Tan
2020-08-11 22:52   ` [PATCH v2 2/7] fetch: allow refspecs specified through stdin Jonathan Tan
2020-08-11 22:52   ` [PATCH v2 3/7] fetch: avoid reading submodule config until needed Jonathan Tan
2020-08-12 17:34     ` Junio C Hamano
2020-08-11 22:52   ` [PATCH v2 4/7] fetch: only populate existing_refs if needed Jonathan Tan
2020-08-12 18:06     ` Junio C Hamano
2020-08-11 22:52   ` [PATCH v2 5/7] fetch-pack: do not lazy-fetch during ref iteration Jonathan Tan
2020-08-12 18:25     ` Junio C Hamano
2020-08-11 22:52   ` [PATCH v2 6/7] promisor-remote: lazy-fetch objects in subprocess Jonathan Tan
2020-08-12 18:28     ` Junio C Hamano
2020-08-11 22:52   ` [PATCH v2 7/7] fetch-pack: remove no_dependents code Jonathan Tan
2020-08-12 12:51   ` [PATCH v2 0/7] Lazy fetch with subprocess Derrick Stolee
2020-08-18  4:01 ` [PATCH v3 " Jonathan Tan
2020-08-18  4:01   ` [PATCH v3 1/7] negotiator/noop: add noop fetch negotiator Jonathan Tan
2020-08-18  4:01   ` [PATCH v3 2/7] fetch: allow refspecs specified through stdin Jonathan Tan
2020-08-18  4:01   ` [PATCH v3 3/7] fetch: avoid reading submodule config until needed Jonathan Tan
2020-08-18  4:01   ` [PATCH v3 4/7] fetch: only populate existing_refs if needed Jonathan Tan
2020-08-18  4:01   ` [PATCH v3 5/7] fetch-pack: do not lazy-fetch during ref iteration Jonathan Tan
2020-08-18  4:01   ` [PATCH v3 6/7] promisor-remote: lazy-fetch objects in subprocess Jonathan Tan
2020-08-18  4:01   ` [PATCH v3 7/7] fetch-pack: remove no_dependents code Jonathan Tan
2020-08-18 19:56   ` [PATCH v3 0/7] Lazy fetch with subprocess Junio C Hamano
2020-08-18 22:32     ` Junio C Hamano
2020-08-18 23:36       ` [PATCH] fixup! promisor-remote: lazy-fetch objects in subprocess Jonathan Tan
2020-08-18 23:57         ` Junio C Hamano

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