Re: [PATCH 0/9] Prefix-compress on-disk index entries

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Nguyen Thai Ngoc Duy <pclouds@xxxxxxxxx> writes:

> On Wed, Apr 4, 2012 at 5:53 AM, Junio C Hamano <gitster@xxxxxxxxx> wrote:
> ...
> I wonder what causes user time drop from .29s to .13s here. I think
> the main patch should increase computation, even only slightly, not
> less.

The main patch reduced the amount of the data needs to be sent to the
machinery to checksum and write to disk by about 45%, saving both I/O
and computation.

This is a tangent, but I wonder why we are not using csum-file API to do
this (I know the dircache code came first way before csum-file; I am
wondering why we haven't rewritten the codepath using it later).

> Anything else you have in mind for v4? Any chance we can adopt crc32
> instead of sha-1?

I am not interested in sacrificing integrity over unproven/unmeasured
performance "issues" on SHA-1, so I am not planning to experiment with
such a change myself.  The choice of hashing algorithm from my point of
view is the least interesting part.


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