From: Junio C Hamano <gitster@pobox.com>
To: Brandon Williams <bmwill@google.com>
Cc: git@vger.kernel.org, pclouds@gmail.com, sbeller@google.com
Subject: Re: [PATCH 25/27] attr: store attribute stacks in hashmap
Date: Fri, 13 Jan 2017 13:20:50 -0800 [thread overview]
Message-ID: <xmqqshomejwt.fsf@gitster.mtv.corp.google.com> (raw)
In-Reply-To: <20170112235354.153403-26-bmwill@google.com> (Brandon Williams's message of "Thu, 12 Jan 2017 15:53:52 -0800")
Brandon Williams <bmwill@google.com> writes:
> The last big hurdle towards a thread-safe API for the attribute system
> is the reliance on a global attribute stack that is modified during each
> call into the attribute system.
>
> This patch removes this global stack and instead a stack is retrieved or
> constructed locally. Since each of these stacks is only used as a
> read-only structure once constructed, they can be stored in a hashmap
> and shared between threads.
Very good.
The reason why the original code used a stack was because it wanted
to keep only the info read from releavant files in-core, discarding
ones from files no-longer relevant (because the traversal switched
to another subdirectory of the same parent directory), to avoid the
memory consumption grow unbounded. It probably was a premature
"optimization" that we can do without, so keeping everything we have
read so far in a hashmap (which is my understanding of what is going
on in this patch) is probably OK.
I suspect that this hashmap may eventually need to become per
attr_check if we want to follow through the optimization envisioned
by patch 15/27.
Inside fill(), path_matches() is called for the number of match_attr
in the entire attribute stack but it is wasteful to check if the
path matches with the a.u.pat if none of the a.state[] entries talk
about attributes and macros that are eventually get used by the
caller of check_attr(). By introducing a wrapping structure, 15/27
wanted to make sure that we have a place to store a "reduced"
attribute stack that is kept per attr_check that has only entries
from the files that talk about the attributes the particular
attr_check wants to learn about.
I need to think about this a bit more, but I do not offhand think
that it makes future such enhancement to make it per-check harder to
move from a global stack to a global hashmap, i.e. the above is not
an objection to this step.
> One caveat with storing and sharing the stack frames like this is that
> the info stack needs to be treated separately from the rest of the
> attribute stack. This is because each stack frame holds a pointer to
> the stack that comes before it and if it was placed on top of the rest
> of the attribute stack then this pointer would be different for each
> attribute stack and wouldn't be able to be shared between threads. In
> order to allow for sharing the info stack frame it needs to be its own
> isolated frame and can simply be processed first to have the same affect
> of being at the top of the stack.
Good.
Thanks.
next prev parent reply other threads:[~2017-01-13 21:20 UTC|newest]
Thread overview: 111+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-01-12 23:53 [PATCH 00/27] Revamp the attribute system; another round Brandon Williams
2017-01-12 23:53 ` [PATCH 01/27] commit.c: use strchrnul() to scan for one line Brandon Williams
2017-01-12 23:53 ` [PATCH 02/27] attr.c: " Brandon Williams
2017-01-12 23:53 ` [PATCH 03/27] attr.c: update a stale comment on "struct match_attr" Brandon Williams
2017-01-12 23:53 ` [PATCH 04/27] attr.c: explain the lack of attr-name syntax check in parse_attr() Brandon Williams
2017-01-12 23:53 ` [PATCH 05/27] attr.c: complete a sentence in a comment Brandon Williams
2017-01-12 23:53 ` [PATCH 06/27] attr.c: mark where #if DEBUG ends more clearly Brandon Williams
2017-01-12 23:53 ` [PATCH 07/27] attr.c: simplify macroexpand_one() Brandon Williams
2017-01-12 23:53 ` [PATCH 08/27] attr.c: tighten constness around "git_attr" structure Brandon Williams
2017-01-12 23:53 ` [PATCH 09/27] attr.c: plug small leak in parse_attr_line() Brandon Williams
2017-01-12 23:53 ` [PATCH 10/27] attr: support quoting pathname patterns in C style Brandon Williams
2017-01-12 23:53 ` [PATCH 11/27] attr.c: add push_stack() helper Brandon Williams
2017-01-12 23:53 ` [PATCH 12/27] Documentation: fix a typo Brandon Williams
2017-01-12 23:53 ` [PATCH 13/27] attr.c: outline the future plans by heavily commenting Brandon Williams
2017-01-12 23:53 ` [PATCH 14/27] attr: rename function and struct related to checking attributes Brandon Williams
2017-01-12 23:53 ` [PATCH 15/27] attr: (re)introduce git_check_attr() and struct attr_check Brandon Williams
2017-01-12 23:53 ` [PATCH 16/27] attr: convert git_all_attrs() to use "struct attr_check" Brandon Williams
2017-01-12 23:53 ` [PATCH 17/27] attr: convert git_check_attrs() callers to use the new API Brandon Williams
2017-01-12 23:53 ` [PATCH 18/27] attr: retire git_check_attrs() API Brandon Williams
2017-01-12 23:53 ` [PATCH 19/27] attr: pass struct attr_check to collect_some_attrs Brandon Williams
2017-01-12 23:53 ` [PATCH 20/27] attr: change validity check for attribute names to use positive logic Brandon Williams
2017-01-12 23:53 ` [PATCH 21/27] attr: use hashmap for attribute dictionary Brandon Williams
2017-01-18 20:20 ` Stefan Beller
2017-01-18 20:23 ` Brandon Williams
2017-01-12 23:53 ` [PATCH 22/27] attr: eliminate global check_all_attr array Brandon Williams
2017-01-12 23:53 ` [PATCH 23/27] attr: remove maybe-real, maybe-macro from git_attr Brandon Williams
2017-01-12 23:53 ` [PATCH 24/27] attr: tighten const correctness with git_attr and match_attr Brandon Williams
2017-01-12 23:53 ` [PATCH 25/27] attr: store attribute stacks in hashmap Brandon Williams
2017-01-13 21:20 ` Junio C Hamano [this message]
2017-01-18 20:34 ` Brandon Williams
2017-01-23 18:08 ` Brandon Williams
2017-01-18 20:39 ` Stefan Beller
2017-01-18 20:45 ` Stefan Beller
2017-01-18 20:50 ` Brandon Williams
2017-01-12 23:53 ` [PATCH 26/27] attr: push the bare repo check into read_attr() Brandon Williams
2017-01-12 23:53 ` [PATCH 27/27] attr: reformat git_attr_set_direction() function Brandon Williams
2017-01-15 23:47 ` [PATCH 00/27] Revamp the attribute system; another round Junio C Hamano
2017-01-16 8:10 ` Jeff King
2017-01-23 20:34 ` [PATCH v2 " Brandon Williams
2017-01-23 20:34 ` [PATCH v2 01/27] commit.c: use strchrnul() to scan for one line Brandon Williams
2017-01-23 20:35 ` [PATCH v2 02/27] attr.c: " Brandon Williams
2017-01-23 20:35 ` [PATCH v2 03/27] attr.c: update a stale comment on "struct match_attr" Brandon Williams
2017-01-23 20:35 ` [PATCH v2 04/27] attr.c: explain the lack of attr-name syntax check in parse_attr() Brandon Williams
2017-01-23 20:35 ` [PATCH v2 05/27] attr.c: complete a sentence in a comment Brandon Williams
2017-01-23 20:35 ` [PATCH v2 06/27] attr.c: mark where #if DEBUG ends more clearly Brandon Williams
2017-01-23 20:35 ` [PATCH v2 07/27] attr.c: simplify macroexpand_one() Brandon Williams
2017-01-23 20:35 ` [PATCH v2 08/27] attr.c: tighten constness around "git_attr" structure Brandon Williams
2017-01-23 20:35 ` [PATCH v2 09/27] attr.c: plug small leak in parse_attr_line() Brandon Williams
2017-01-23 20:35 ` [PATCH v2 10/27] attr: support quoting pathname patterns in C style Brandon Williams
2017-01-23 20:35 ` [PATCH v2 11/27] attr.c: add push_stack() helper Brandon Williams
2017-01-23 20:35 ` [PATCH v2 12/27] Documentation: fix a typo Brandon Williams
2017-01-23 20:35 ` [PATCH v2 13/27] attr.c: outline the future plans by heavily commenting Brandon Williams
2017-01-23 20:35 ` [PATCH v2 14/27] attr: rename function and struct related to checking attributes Brandon Williams
2017-01-23 20:35 ` [PATCH v2 15/27] attr: (re)introduce git_check_attr() and struct attr_check Brandon Williams
2017-01-23 20:35 ` [PATCH v2 16/27] attr: convert git_all_attrs() to use "struct attr_check" Brandon Williams
2017-01-23 20:35 ` [PATCH v2 17/27] attr: convert git_check_attrs() callers to use the new API Brandon Williams
2017-01-23 20:35 ` [PATCH v2 18/27] attr: retire git_check_attrs() API Brandon Williams
2017-01-23 20:35 ` [PATCH v2 19/27] attr: pass struct attr_check to collect_some_attrs Brandon Williams
2017-01-23 20:35 ` [PATCH v2 20/27] attr: change validity check for attribute names to use positive logic Brandon Williams
2017-01-23 20:35 ` [PATCH v2 21/27] attr: use hashmap for attribute dictionary Brandon Williams
2017-01-23 20:35 ` [PATCH v2 22/27] attr: eliminate global check_all_attr array Brandon Williams
2017-01-23 21:11 ` Junio C Hamano
2017-01-23 20:35 ` [PATCH v2 23/27] attr: remove maybe-real, maybe-macro from git_attr Brandon Williams
2017-01-23 20:35 ` [PATCH v2 24/27] attr: tighten const correctness with git_attr and match_attr Brandon Williams
2017-01-23 20:35 ` [PATCH v2 25/27] attr: store attribute stack in attr_check structure Brandon Williams
2017-01-23 21:42 ` Junio C Hamano
2017-01-23 22:06 ` Brandon Williams
2017-01-24 1:11 ` Brandon Williams
2017-01-24 2:28 ` Junio C Hamano
2017-01-25 19:57 ` Brandon Williams
2017-01-25 20:10 ` Stefan Beller
2017-01-25 20:14 ` Junio C Hamano
2017-01-25 21:54 ` Brandon Williams
2017-01-25 23:19 ` Brandon Williams
2017-01-23 20:35 ` [PATCH v2 26/27] attr: push the bare repo check into read_attr() Brandon Williams
2017-01-23 20:35 ` [PATCH v2 27/27] attr: reformat git_attr_set_direction() function Brandon Williams
2017-01-28 2:01 ` [PATCH v3 00/27] Revamp the attribute system; another round Brandon Williams
2017-01-28 2:01 ` [PATCH v3 01/27] commit.c: use strchrnul() to scan for one line Brandon Williams
2017-01-28 2:01 ` [PATCH v3 02/27] attr.c: " Brandon Williams
2017-01-28 2:01 ` [PATCH v3 03/27] attr.c: update a stale comment on "struct match_attr" Brandon Williams
2017-01-28 2:01 ` [PATCH v3 04/27] attr.c: explain the lack of attr-name syntax check in parse_attr() Brandon Williams
2017-01-28 2:01 ` [PATCH v3 05/27] attr.c: complete a sentence in a comment Brandon Williams
2017-01-28 2:01 ` [PATCH v3 06/27] attr.c: mark where #if DEBUG ends more clearly Brandon Williams
2017-01-28 2:01 ` [PATCH v3 07/27] attr.c: simplify macroexpand_one() Brandon Williams
2017-01-28 2:01 ` [PATCH v3 08/27] attr.c: tighten constness around "git_attr" structure Brandon Williams
2017-01-28 2:01 ` [PATCH v3 09/27] attr.c: plug small leak in parse_attr_line() Brandon Williams
2017-01-28 2:01 ` [PATCH v3 10/27] attr: support quoting pathname patterns in C style Brandon Williams
2017-01-28 2:01 ` [PATCH v3 11/27] attr.c: add push_stack() helper Brandon Williams
2017-01-28 2:01 ` [PATCH v3 12/27] Documentation: fix a typo Brandon Williams
2017-01-28 2:01 ` [PATCH v3 13/27] attr.c: outline the future plans by heavily commenting Brandon Williams
2017-01-28 2:01 ` [PATCH v3 14/27] attr: rename function and struct related to checking attributes Brandon Williams
2017-01-28 2:01 ` [PATCH v3 15/27] attr: (re)introduce git_check_attr() and struct attr_check Brandon Williams
2017-01-30 18:05 ` Brandon Williams
2017-01-28 2:01 ` [PATCH v3 16/27] attr: convert git_all_attrs() to use "struct attr_check" Brandon Williams
2017-01-28 23:50 ` Stefan Beller
2017-01-29 2:44 ` Brandon Williams
2017-01-30 18:06 ` Brandon Williams
2017-01-28 2:01 ` [PATCH v3 17/27] attr: convert git_check_attrs() callers to use the new API Brandon Williams
2017-01-28 2:01 ` [PATCH v3 18/27] attr: retire git_check_attrs() API Brandon Williams
2017-01-28 2:01 ` [PATCH v3 19/27] attr: pass struct attr_check to collect_some_attrs Brandon Williams
2017-01-28 2:02 ` [PATCH v3 20/27] attr: change validity check for attribute names to use positive logic Brandon Williams
2017-01-28 2:02 ` [PATCH v3 21/27] attr: use hashmap for attribute dictionary Brandon Williams
2017-01-28 2:02 ` [PATCH v3 22/27] attr: eliminate global check_all_attr array Brandon Williams
2017-01-28 2:02 ` [PATCH v3 23/27] attr: remove maybe-real, maybe-macro from git_attr Brandon Williams
2017-01-28 2:02 ` [PATCH v3 24/27] attr: tighten const correctness with git_attr and match_attr Brandon Williams
2017-01-28 2:02 ` [PATCH v3 25/27] attr: store attribute stack in attr_check structure Brandon Williams
2017-01-28 2:02 ` [PATCH v3 26/27] attr: push the bare repo check into read_attr() Brandon Williams
2017-01-28 2:02 ` [PATCH v3 27/27] attr: reformat git_attr_set_direction() function Brandon Williams
2017-02-02 19:14 ` [PATCH v3 00/27] Revamp the attribute system; another round Junio C Hamano
2017-02-09 17:18 ` Brandon Williams
2017-02-09 19:31 ` Junio C Hamano
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