From: Thomas Gummerer <t.gummerer@gmail.com>
To: Jeff King <peff@peff.net>
Cc: Jeff Hostetler <git@jeffhostetler.com>,
git@vger.kernel.org, gitster@pobox.com,
Jeff Hostetler <jeffhost@microsoft.com>
Subject: Re: [PATCH v3 0/2] read-cache: call verify_hdr() in a background thread
Date: Thu, 30 Mar 2017 21:06:48 +0100 [thread overview]
Message-ID: <20170330200648.GH27158@hank> (raw)
In-Reply-To: <20170328195605.xy4pnhy74s6wgwps@sigill.intra.peff.net>
On 03/28, Jeff King wrote:
> On Tue, Mar 28, 2017 at 03:50:34PM -0400, Jeff Hostetler wrote:
>
> > It was a convenient way to isolate, average, and compare
> > read_index() times, but I suppose we could do something
> > like that.
> >
> > I did confirm that a ls-files does show a slight 0.008
> > second difference on the 58K file Linux tree when toggled
> > on or off.
>
> Yeah, I agree it helps isolate the change. I'm just not sure we want to
> carry a bunch of function-specific perf-testing code. And one of the
> nice things about testing a real command is that it's...a real command.
> So it's an actual improvement a user might see.
>
> > But I'm tempted to suggest that we just omit my helper exe
> > and not worry about a test -- since we don't have any test
> > repos large enough to really demonstrate the differences.
> > My concern is that that 0.008 would be lost in the noise
> > of the rest of the test and make for an unreliable result.
>
> Yeah, I think that would be fine. You _could_ write a t/perf test and
> then use your 400MB monstrosity as GIT_PERF_LARGE_REPO. But given that
> most people don't have such a thing, there's not much value over you
> just showing off the perf improvement in the commit message.
Sorry if this was already discussed, but we already do have a perf
test for the index (p0002), and a corresponding helper program which
just does read_cache() and discard_cache(). Maybe we could re-use
that and add a second test running the same using the new config?
> We could also have a t/perf test that generates a monstrous index and
> shows that it's faster. But frankly, I don't think this is all that
> interesting as a performance regression test. It's not like there's
> something subtle about the performance improvement; we stopped computing
> the SHA-1, and (gasp!) it takes exactly one SHA-1 computation's less
> time.
>
> So just mentioning the test case and the improvement in the commit
> message is sufficient, IMHO.
>
> -Peff
next prev parent reply other threads:[~2017-03-30 20:06 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-03-28 19:07 [PATCH v3 0/2] read-cache: call verify_hdr() in a background thread git
2017-03-28 19:07 ` [PATCH v3 1/2] read-cache: core.checksumindex git
2017-03-28 19:07 ` [PATCH v3 2/2] test-core-checksum-index: core.checksumindex test helper git
2017-03-28 19:16 ` [PATCH v3 0/2] read-cache: call verify_hdr() in a background thread Jeff King
2017-03-28 19:50 ` Jeff Hostetler
2017-03-28 19:56 ` Jeff King
2017-03-30 19:49 ` Junio C Hamano
2017-03-30 19:58 ` Jeff King
2017-03-30 20:44 ` Junio C Hamano
2017-03-31 13:20 ` Jeff Hostetler
2017-03-30 20:06 ` Thomas Gummerer [this message]
2017-03-30 20:39 ` Jeff King
2017-03-31 13:23 ` Jeff Hostetler
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