From: Jeff King <peff@peff.net>
To: Junio C Hamano <gitster@pobox.com>
Cc: "Michael Haggerty" <mhagger@alum.mit.edu>,
"Nguyễn Thái Ngọc Duy" <pclouds@gmail.com>,
"Stefan Beller" <sbeller@google.com>,
"Johannes Schindelin" <Johannes.Schindelin@gmx.de>,
"David Turner" <novalis@novalis.org>,
git@vger.kernel.org
Subject: Re: [PATCH 1/5] refs: store submodule ref stores in a hashmap
Date: Thu, 9 Feb 2017 23:04:00 -0500 [thread overview]
Message-ID: <20170210040400.kf6hurtcblnoxdqi@sigill.intra.peff.net> (raw)
In-Reply-To: <xmqqh943p0hv.fsf@gitster.mtv.corp.google.com>
On Thu, Feb 09, 2017 at 12:34:04PM -0800, Junio C Hamano wrote:
> > +static struct submodule_hash_entry *alloc_submodule_hash_entry(
> > + const char *submodule, struct ref_store *refs)
> > +{
> > + size_t len = strlen(submodule);
> > + struct submodule_hash_entry *entry = malloc(sizeof(*entry) + len + 1);
>
> I think this (and the later memcpy) is what FLEX_ALLOC_MEM() was
> invented for.
Yes, it was. Though since the length comes from a strlen() call, it can
actually use the _STR variant, like:
FLEX_ALLOC_STR(entry, submodule, submodule);
Besides being shorter, this does integer-overflow checks on the final
length.
> > @@ -1373,16 +1405,17 @@ void base_ref_store_init(struct ref_store *refs,
> > die("BUG: main_ref_store initialized twice");
> >
> > refs->submodule = "";
> > - refs->next = NULL;
> > main_ref_store = refs;
> > } else {
> > - if (lookup_ref_store(submodule))
> > + refs->submodule = xstrdup(submodule);
> > +
> > + if (!submodule_ref_stores.tablesize)
> > + hashmap_init(&submodule_ref_stores, submodule_hash_cmp, 20);
>
> Makes me wonder what "20" stands for. Perhaps the caller should be
> allowed to say "I do not quite care what initial size is" by passing
> 0 or some equally but more clealy meaningless value (which of course
> would be outside the scope of this series).
I think this is what "0" already does (grep for HASHMAP_INITIAL_SIZE).
In fact, that constant is 64. The 20 we pass in goes through some magic
load-factor computation and ends up as 25. That being smaller than the
INITIAL_SIZE constant, I believe that we end up allocating 64 entries
either way (that's just from reading the code, though; I didn't run it
to double check).
-Peff
next prev parent reply other threads:[~2017-02-10 4:41 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-02-09 13:26 [PATCH 0/5] Store submodules in a hash, not a linked list Michael Haggerty
2017-02-09 13:26 ` [PATCH 1/5] refs: store submodule ref stores in a hashmap Michael Haggerty
2017-02-09 16:58 ` Stefan Beller
2017-02-09 17:40 ` Michael Haggerty
2017-02-09 17:43 ` Stefan Beller
2017-02-09 19:32 ` Jeff King
2017-02-09 20:34 ` Junio C Hamano
2017-02-10 4:04 ` Jeff King [this message]
2017-02-10 10:23 ` Michael Haggerty
2017-02-09 13:26 ` [PATCH 2/5] refs: push the submodule attribute down Michael Haggerty
2017-02-09 17:03 ` Stefan Beller
2017-02-09 21:07 ` Junio C Hamano
2017-02-09 13:27 ` [PATCH 3/5] register_ref_store(): new function Michael Haggerty
2017-02-09 17:20 ` Stefan Beller
2017-02-09 18:14 ` Michael Haggerty
2017-02-09 21:16 ` Junio C Hamano
2017-02-09 13:27 ` [PATCH 4/5] files_ref_store::submodule: use NULL for the main repository Michael Haggerty
2017-02-09 17:25 ` Stefan Beller
2017-02-09 21:19 ` Junio C Hamano
2017-02-09 21:36 ` Stefan Beller
2017-02-09 13:27 ` [PATCH 5/5] read_loose_refs(): read refs using resolve_ref_recursively() Michael Haggerty
2017-02-09 17:39 ` Stefan Beller
2017-02-09 19:48 ` [PATCH 0/5] Store submodules in a hash, not a linked list Junio C Hamano
2017-02-09 19:58 ` Jeff King
2017-02-09 21:23 ` Michael Haggerty
2017-02-10 0:40 ` Jeff King
2017-02-10 10:27 ` Michael Haggerty
2017-02-13 2:39 ` Duy Nguyen
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