Re: [PATCH 1/1] commit-graph.c: avoid unnecessary tag dereference when merging

From: Jeff King <peff@peff.net>
Date: Mar 24, 2020, 06:06 UTC
Message-ID: <20200324060637.GB610977@coredump.intra.peff.net>
In-Reply-To: <20200322164531.GA55067@syl.local>

On Sun, Mar 22, 2020 at 10:45:31AM -0600, Taylor Blau wrote:

Show 5 quoted lines

> So, I'm not sure what was going on with my original measurements, other
> than that I took them around midnight, so the chance for error was
> probably high. I'll go with your measurements, since they are both
> closer to what we'd see in the real world, and actually representative
> of the change here.

I wondered if perhaps you had stray commit-graph files sitting around. I don't think we'd look at them if they aren't mentioned in the commit-graphs index, though. And anyway, feeding all of the packed objects would mean those would all be parsed in the earlier stage, so even if we _did_ have a bunch of stuff to merge, it would have been fast even with the old code.

So...I dunno.

One other thing that's bitten me in the past is accidentally compiling with the wrong optimization settings. I have my config.mak set up to compile with -O0 by default (because it's faster and because I'm frequently debugging anyway), and then I do a -O2 build for my daily driver. But when performance testing, I sometimes accidentally compare -O0 and -O2 builds to each other. That's all very specific to my config.mak setup, but I know you've picked up some of it, so it's possible you inherited that subtlety. :)

-Peff