Re: [PATCH 0/5] A series of performance enhancements in the memihash and name-cache area

From: Jeff Hostetler <git@jeffhostetler.com>
Date: Feb 15, 2017, 14:27 UTC
Message-ID: <16b1259c-4cdc-8f4d-db47-d724386a3d2b@jeffhostetler.com>
In-Reply-To: <20170214220332.753i4tgclm62er4f@sigill.intra.peff.net>

On 2/14/2017 5:03 PM, Jeff King wrote:

Show 17 quoted lines

> On Tue, Feb 14, 2017 at 12:31:46PM +0100, Johannes Schindelin wrote:
>
>> On Windows, calls to memihash() and maintaining the istate.name_hash and
>> istate.dir_hash HashMaps take significant time on very large
>> repositories. This series of changes reduces the overall time taken for
>> various operations by reducing the number calls to memihash(), moving
>> some of them into multi-threaded code, and etc.
>>
>> Note: one commenter in https://github.com/git-for-windows/git/pull/964
>> pointed out that memihash() only handles ASCII correctly. That is true.
>> And fixing this is outside the purview of this patch series.
> Out of curiosity, do you have numbers? Bonus points if the speedup can
> be shown via a t/perf script.
>
> We have a read-cache perf-test already, but I suspect you'd want
> something more like "git status" or "ls-files -o" that calls into
> read_directory().

I have some informal numbers in a spreadsheet. I was seeing a 8-9% speed up on a status on my gigantic repo.

I'll try to put together a before/after perf-test to better demonstrate this.

Jeff