Re: [PATCH v1] add: speed up cmd_add() by utilizing read_cache_preload()

From: Duy Nguyen <pclouds@gmail.com>
Date: Nov 3, 2018, 04:47 UTC
Message-ID: <CACsJy8AZ4kxrpttfsHOWKP=Xg3HaTLySy7sepC5691mGzfgO5g@mail.gmail.com>
In-Reply-To: <xmqqmuqrngfu.fsf@gitster-ct.c.googlers.com>

On Sat, Nov 3, 2018 at 1:38 AM Junio C Hamano <gitster@pobox.com> wrote:

Show 19 quoted lines

>
> 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.

Ah. I keep forgetting read_cache_preload is loading the index _and_ refreshing. I thought the two had some different semantics but failed to see it last time.

-- 
Duy