From: Shawn Pearce <spearce@spearce.org>
Date: Mon, 08 Jul 2013 15:54:24 GMT
Subject: expanding pack idx fanout table
Message-ID: <CAJo=hJsto1ik=GTC8c3+2_jBuUqcAPL0UWp-1uoYYMpgbLB+qg@mail.gmail.com>

Has anyone studied the impact of converting the pack idx fanout table
from 256 entries to 65536 entries?

Back of the envelope estimates for 3.1M objects in linux.git suggests
a 2^16 fanout table would decrease the number of binary search
iterations from ~14 to ~6. The increased table costs an extra 255 KiB
of disk. On a 70M idx file this is noise.

I'm starting to wonder if increasing the fanout table once the object
count is above a certain threshold is a reasonable optimization for
larger repositories.