[PATCH 3 of 4 tags-cache-split] tags: extract .hgtags filenodes cache to a standalone file

[Pierre-Yves David]

On 03/31/2015 06:19 AM, Matt Mackall wrote:
> On Sun, 2015-03-29 at 23:14 -0700, Gregory Szorc wrote:
>> # HG changeset patch
>> # User Gregory Szorc <gregory.szorc at gmail.com>
>> # Date 1426392860 25200
>> #      Sat Mar 14 21:14:20 2015 -0700
>> # Node ID 9b396004b4338aa3e011cbf4f13800a3c55b1ab6
>> # Parent  c19ef55be215f68a0955c49473c2e07b721998ff
>> tags: extract .hgtags filenodes cache to a standalone file
>>
>> Resolution of .hgtags filenodes values has historically been
>> a performance pain point for large repositories, where reading
>> individual manifests can take over 100ms. Multiplied by hundreds
>> or even thousands of heads and resolving .hgtags filenodes becomes
>> a performance issue.
>>
>> Earlier work to split the tags cache into per-filter files
>> helped alleviate many of the pain points. However, it didn't
>> address the overall problem of redundant .hgtags filenode resolution.
>> In fact, it introduced a new one: redundant .hgtags filenode
>> resolution for each per-filter cache file.
>
> Again, please take a look at the new revbranchcache and either try to
> parallel it or explain why you're doing something different. It's
> already doing the same thing for rev->branch names that you're doing
> for .hgtags nodes, compactly and quickly.

I've spend some time in VC with greg, to talk about how reb branch cache 
collaborate and how such approach could also be used by tags cache.

Collaboration is now clearer in Greg minds while the way the tag cache 
is clearer in mind. There will be a new version of this series.

-- 
Pierre-Yves David