From: Michael Haggerty <mhagger@alum.mit.edu>
To: Junio C Hamano <gitster@pobox.com>
Cc: git@vger.kernel.org, Jeff King <peff@peff.net>,
Drew Northup <drew.northup@maine.edu>,
Jakub Narebski <jnareb@gmail.com>,
Heiko Voigt <hvoigt@hvoigt.net>
Subject: Re: [PATCH 6/6] Retain caches of submodule refs
Date: Sun, 09 Oct 2011 13:12:20 +0200 [thread overview]
Message-ID: <4E918194.5060102@alum.mit.edu> (raw)
In-Reply-To: <7v4o1hgemp.fsf@alter.siamese.dyndns.org>
On 08/17/2011 12:45 AM, Junio C Hamano wrote:
> All the changes except for this one made sense to me, but I am not sure
> about this one. How often do we look into different submodule refs in the
> same process over and over again?
I am having pangs of uncertainty about this patch.
Previous to this patch, the submodule reference cache was only used for
the duration of one call to do_for_each_ref(). (It was not *discarded*
until later, but the old cache was never reused.) Therefore, the
submodule reference cache was implicitly invalidated between successive
uses.
After this change, submodule ref caches are invalidated whenever
invalidate_cached_refs() is called. But this function is static, and it
is only called when main-module refs are changed.
AFAIK there is no way within refs.c to add, modify, or delete a
submodule reference. But if other code modifies submodule references
directly, then the submodule ref cache in refs.c would become stale.
Moreover, there is currently no API for invalidating the cache.
So I think I need help from a submodule guru (Heiko?) who can tell me
what is done with submodule references and whether they might be
modified while a git process is executing in the main module. If so,
then either this patch has to be withdrawn, or more work has to be put
in to make such code invalidate the submodule reference cache.
Sorry for the oversight, but I forgot that not all code necessarily uses
the refs.c API when dealing with references (a regrettable situation, BTW).
Michael
--
Michael Haggerty
mhagger@alum.mit.edu
http://softwareswirl.blogspot.com/
next prev parent reply other threads:[~2011-10-09 11:13 UTC|newest]
Thread overview: 54+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-08-12 22:36 [PATCH 0/6] Retain caches of submodule refs Michael Haggerty
2011-08-12 22:36 ` [PATCH 1/6] Extract a function clear_cached_refs() Michael Haggerty
2011-08-12 22:36 ` [PATCH 2/6] Access reference caches only through new function get_cached_refs() Michael Haggerty
2011-08-14 22:12 ` Junio C Hamano
2011-08-23 4:21 ` Michael Haggerty
2011-08-12 22:36 ` [PATCH 3/6] Change the signature of read_packed_refs() Michael Haggerty
2011-08-12 22:36 ` [PATCH 4/6] Allocate cached_refs objects dynamically Michael Haggerty
2011-08-14 22:21 ` Junio C Hamano
2011-08-12 22:36 ` [PATCH 5/6] Store the submodule name in struct cached_refs Michael Haggerty
2011-08-12 22:36 ` [PATCH 6/6] Retain caches of submodule refs Michael Haggerty
2011-08-13 12:54 ` Heiko Voigt
2011-08-24 8:17 ` Michael Haggerty
2011-08-24 20:05 ` Heiko Voigt
2011-08-16 22:45 ` Junio C Hamano
2011-08-24 11:33 ` Michael Haggerty
2011-10-09 11:12 ` Michael Haggerty [this message]
2011-10-09 20:10 ` Junio C Hamano
2011-10-10 5:46 ` [PATCH 0/2] Provide API to invalidate refs cache Michael Haggerty
2011-10-10 5:46 ` [PATCH 1/2] invalidate_cached_refs(): take the submodule as parameter Michael Haggerty
2011-10-10 5:46 ` [PATCH 2/2] invalidate_cached_refs(): expose this function in refs API Michael Haggerty
2011-10-10 8:24 ` [PATCH v2 0/7] Provide API to invalidate refs cache Michael Haggerty
2011-10-10 8:24 ` [PATCH v2 1/7] invalidate_ref_cache(): rename function from invalidate_cached_refs() Michael Haggerty
2011-10-11 0:00 ` Junio C Hamano
2011-10-11 5:53 ` Michael Haggerty
2011-10-10 8:24 ` [PATCH v2 2/7] invalidate_ref_cache(): take the submodule as parameter Michael Haggerty
2011-10-10 8:24 ` [PATCH v2 3/7] invalidate_ref_cache(): expose this function in refs API Michael Haggerty
2011-10-10 8:24 ` [PATCH v2 4/7] clear_cached_refs(): rename parameter Michael Haggerty
2011-10-10 8:24 ` [PATCH v2 5/7] clear_cached_refs(): extract two new functions Michael Haggerty
2011-10-10 8:24 ` [PATCH v2 6/7] write_ref_sha1(): only invalidate the loose ref cache Michael Haggerty
2011-10-10 8:24 ` [PATCH v2 7/7] clear_cached_refs(): inline function Michael Haggerty
2011-10-11 0:02 ` [PATCH v2 0/7] Provide API to invalidate refs cache Junio C Hamano
2011-10-11 5:50 ` Michael Haggerty
2011-10-11 8:09 ` Julian Phillips
2011-10-11 17:26 ` Junio C Hamano
2011-10-12 18:44 ` [PATCH v3 " Michael Haggerty
2011-10-12 18:44 ` [PATCH v3 1/7] invalidate_ref_cache(): rename function from invalidate_cached_refs() Michael Haggerty
2011-10-12 19:14 ` Junio C Hamano
2011-10-12 22:12 ` Michael Haggerty
2011-10-12 18:44 ` [PATCH v3 2/7] invalidate_ref_cache(): take the submodule as parameter Michael Haggerty
2011-10-12 19:19 ` Junio C Hamano
2011-10-12 22:07 ` Michael Haggerty
2011-10-17 18:00 ` Junio C Hamano
2011-11-03 10:23 ` Michael Haggerty
2011-11-03 18:57 ` Junio C Hamano
2011-10-12 18:44 ` [PATCH v3 3/7] invalidate_ref_cache(): expose this function in refs API Michael Haggerty
2011-10-12 18:44 ` [PATCH v3 4/7] clear_cached_refs(): rename parameter Michael Haggerty
2011-10-12 18:44 ` [PATCH v3 5/7] clear_cached_refs(): extract two new functions Michael Haggerty
2011-10-12 18:44 ` [PATCH v3 6/7] write_ref_sha1(): only invalidate the loose ref cache Michael Haggerty
2011-10-12 18:44 ` [PATCH v3 7/7] clear_cached_refs(): inline function Michael Haggerty
2011-10-12 19:28 ` [PATCH v3 0/7] Provide API to invalidate refs cache Junio C Hamano
2011-10-10 19:53 ` Re: [PATCH 6/6] Retain caches of submodule refs Heiko Voigt
2011-10-11 4:12 ` Michael Haggerty
2011-10-11 17:41 ` Heiko Voigt
2011-08-13 12:34 ` [PATCH 0/6] " Heiko Voigt
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