Re: [PATCH v2 05/38] refs: create a base class "ref_store" for files_ref_store

From: Michael Haggerty <mhagger@alum.mit.edu>
Date: Sep 5, 2016, 03:53 UTC
Message-ID: <c6ae77bf-e2e2-c108-648d-75b5164b7ba2@alum.mit.edu>
In-Reply-To: <1473021637.6035.27.camel@frank>

On 09/04/2016 10:40 PM, David Turner wrote:

Show 9 quoted lines

> On Sun, 2016-09-04 at 18:08 +0200, Michael Haggerty wrote:
> 
>> +/* A linked list of ref_stores for submodules: */
>> +static struct ref_store *submodule_ref_stores;
> 
> I don't like the per-submodule stores being in a linked list, which
> requires a linear search.  Stefan has, I think, been doing a bunch of
> work to scale git to support on the order of thousands of submodules,
> which this potentially breaks.  What about a hashmap?

I agree it's not ideal, but this linked list is not new. Before this patch the same code was in `files-backend.c`, and before patch [03/38] essentially the same linked list was stored as `submodule_ref_caches`. So this is not a regression, and I'd rather not address it in this patch series.

CC Stefan in case he'd like to put it on his radar. Honestly, I've never checked how often the submodule reference cache is used in real life.

Michael