From: Junio C Hamano <gitster@pobox.com>
Date: Sat, 03 Nov 2018 00:38:29 GMT
Subject: Re: [PATCH v1] add: speed up cmd_add() by utilizing read_cache_preload()
Message-ID: <xmqqmuqrngfu.fsf@gitster-ct.c.googlers.com>
In-Reply-To: <CACsJy8CVPSe8TWYMrK9MiRCaG36qyWfd42cEPo5844XWuTmqew@mail.gmail.com>

Duy Nguyen <pclouds@gmail.com> writes:

> On Fri, Nov 2, 2018 at 2:32 PM Ben Peart <peartben@gmail.com> wrote:
>>
>> From: Ben Peart <benpeart@microsoft.com>
>>
>> During an "add", a call is made to run_diff_files() which calls
>> check_remove() for each index-entry.  The preload_index() code distributes
>> some of the costs across multiple threads.
>
> Instead of doing this site by site. How about we make read_cache()
> always do multithread preload?

I suspect that it would be a huge performance killer. 

Many codepaths do not even want to know if the working tree files
have been modified, even though they need to know what's in the
index.  Think "git commit-tree", "git diff --cached", etc.