From: Junio C Hamano <gitster@pobox•com>
To: Duy Nguyen <pclouds@gmail•com>
Cc: "brian m. carlson" <sandals@crustytoothpaste•net>,
Michael Haggerty <mhagger@alum•mit.edu>,
"Kyle J. McKay" <mackyle@gmail•com>,
Git Mailing List <git@vger•kernel.org>,
Andreas Schwab <schwab@linux-m68k•org>
Subject: Re: [PATCH v2 01/10] Define a structure for object IDs.
Date: Sat, 14 Mar 2015 15:19:03 -0700 [thread overview]
Message-ID: <xmqqbnjvw7c8.fsf@gitster.dls.corp.google.com> (raw)
In-Reply-To: <CACsJy8BeFO3RQJ6pU5+q6E4n3A36X9PgYoi7xB_NQ4C_JYaP5w@mail.gmail.com> (Duy Nguyen's message of "Sat, 14 Mar 2015 18:49:51 +0700")
Duy Nguyen <pclouds@gmail•com> writes:
>> Anyway, wouldn't this be all academic? I do not see how you would
>> keep the object name in the <pack, nth> format in-core, as the
>> obj_hash[] is a hashtable keyed by <sha-1>, and even when we switch
>> to a different hash, I cannot see how such a table to ensure the
>> singleton-ness of in-core objects can be keyed sometimes by <hash>
>> and by <pack, nth> in some other time.
>
> I'm implementing something to see how much we gain by avoiding object
> lookup. The current approach is having "struct object ** obj" in
> "struct packed_git", indexed by "nth". So when you have <pack, nth>
> and pack->obj[nth] is valid, you'll get to "struct object *" without
> hashing.
But do you realize that the hashtable serves two purposes? Grab the
object from its name is one thing, and the other one I am not seeing
how you will make it work with "sometimes <sha-1> sometimes <pack,nth>"
is to ensure that we will have only one in-core copy for the same object.
We even walk the hashtable when we want to drop the flag bits from
all in-core objects, so even if you instanciated an in-core object
without going through the object name layer, the hashtable needs to
have a pointer to such a pointer, no?
next prev parent reply other threads:[~2015-03-14 22:19 UTC|newest]
Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-03-07 23:23 [PATCH v2 00/10] Use a structure for object IDs brian m. carlson
2015-03-07 23:23 ` [PATCH v2 01/10] Define " brian m. carlson
[not found] ` <CEA07500-9F47-4B24-AD5D-1423A601A4DD@gmail.com>
2015-03-11 22:08 ` brian m. carlson
2015-03-12 0:26 ` Junio C Hamano
2015-03-12 9:34 ` brian m. carlson
2015-03-12 10:28 ` Michael Haggerty
2015-03-12 10:46 ` brian m. carlson
2015-03-12 11:16 ` Duy Nguyen
2015-03-12 18:24 ` Junio C Hamano
2015-03-12 18:44 ` Junio C Hamano
2015-03-13 0:58 ` Duy Nguyen
2015-03-13 6:03 ` Junio C Hamano
2015-03-14 11:49 ` Duy Nguyen
2015-03-14 22:19 ` Junio C Hamano [this message]
2015-03-15 0:17 ` Duy Nguyen
2015-03-15 2:32 ` Junio C Hamano
2015-03-07 23:23 ` [PATCH v2 02/10] Define utility functions " brian m. carlson
2015-03-08 9:57 ` Duy Nguyen
2015-03-08 14:48 ` brian m. carlson
2015-03-11 12:44 ` Michael Haggerty
2015-03-07 23:23 ` [PATCH v2 03/10] bisect.c: convert leaf functions to use struct object_id brian m. carlson
2015-03-07 23:23 ` [PATCH v2 04/10] archive.c: convert " brian m. carlson
2015-03-11 14:20 ` Michael Haggerty
2015-03-11 22:12 ` brian m. carlson
2015-03-07 23:24 ` [PATCH v2 05/10] zip: use GIT_SHA1_HEXSZ for trailers brian m. carlson
2015-03-07 23:24 ` [PATCH v2 06/10] bulk-checkin.c: convert to use struct object_id brian m. carlson
2015-03-07 23:24 ` [PATCH v2 07/10] diff: convert struct combine_diff_path to object_id brian m. carlson
2015-03-07 23:24 ` [PATCH v2 08/10] commit: convert parts to struct object_id brian m. carlson
2015-03-11 14:46 ` Michael Haggerty
2015-03-07 23:24 ` [PATCH v2 09/10] patch-id: convert to use " brian m. carlson
2015-03-07 23:24 ` [PATCH v2 10/10] apply: convert threeway_stage to object_id brian m. carlson
2015-03-08 7:43 ` [PATCH v2 00/10] Use a structure for object IDs Junio C Hamano
2015-03-11 2:38 ` Kyle J. McKay
2015-03-11 16:08 ` Michael Haggerty
2015-03-11 20:35 ` Junio C Hamano
2015-03-13 22:45 ` brian m. carlson
-- strict thread matches above, loose matches on Subject: below --
2015-03-13 23:39 brian m. carlson
2015-03-13 23:39 ` [PATCH v2 01/10] Define " brian m. carlson
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