Re: [PATCH] refs: fix interleaving hook calls with reference-transaction hook

From: Junio C Hamano <gitster@pobox.com>
Date: Aug 7, 2020, 17:32 UTC
Message-ID: <xmqqpn82gy51.fsf@gitster.c.googlers.com>
In-Reply-To: <20200807094946.GA1758126@tanuki.pks.im>

Patrick Steinhardt <ps@pks.im> writes:

Show 16 quoted lines

> On Fri, Aug 07, 2020 at 05:32:39AM -0400, Jeff King wrote:
>
>> That implies you're just seeing noise. And indeed, with the patch below
>> I get:
>> 
>> Test                         HEAD^             HEAD
>> --------------------------------------------------------------------
>> 1400.2: update-ref           1.93(1.57+0.42)   1.91(1.55+0.42) -1.0%
>> 1400.3: update-ref --stdin   0.07(0.02+0.05)   0.07(0.02+0.05) +0.0%
>> 
>> Running it a second time gets me +0.5%. :)
>
> Yeah, it's also been my take that OS-level overhead is probably going to
> matter more than those access calls, and I argued such back when I
> proposed the hook. So I'm perfectly happy to see this caching mechanism
> go.

Is the above about negative cache? IOW, does the above demonstrate that one extra access() to make sure there is no hook does not hurt us anything?

If so, yes, I am 100% for removing the cache mechanism.

Thanks for driving design decision with numbers. That's always pleasant to see.