From: Elijah Newren <newren@gmail.com>
Date: Sun, 22 Jul 2018 06:22:10 GMT
Subject: Re: [PATCH] pack-objects: fix performance issues on packing large deltas
Message-ID: <CABPp-BHecS-TewK=tCxEZkCiM_QF=Pj3LkDWOT6+2F1VCu-KcQ@mail.gmail.com>
In-Reply-To: <20180721044711.GA31376@duynguyen.home>

On Fri, Jul 20, 2018 at 9:47 PM, Duy Nguyen <pclouds@gmail.com> wrote:
> On Fri, Jul 20, 2018 at 10:43:25AM -0700, Elijah Newren wrote:
>> Out of curiosity, would it be possible to use the delta_size_ field
>> for deltas that are small enough, and only use an external data
>> structure (perhaps a hash rather than an array) for the few deltas
>> that are large?
>
> We could. And because repack time is still a bit higher in your
> linux.git case. Let's try this. No locking in common case and very
> small locked region when we hit large deltas

This one looks like a winner.  Labelling this as fix-v7, this rounds
out the table to:

Version  Time (s)
-------  --------
 2.17.0   621.36
 2.18.0   621.80
 fix-v5   836.29
 fix-v6   831.73
 fix-v2   619.96
 fix-v7   622.88

So the runtime is basically within the noise of different runs of the
timing for 2.17.0 or 2.18.0 or -v2, and is much faster than -v5 or
-v6.