Re: [PATCH v2 0/5] New hash table implementation

From: Duy Nguyen <pclouds@gmail.com>
Date: Sep 26, 2013, 11:14 UTC
Message-ID: <CACsJy8C_Rr=2tsi_8TmGnHy85qBND1tNby7Nou4O4eqFTOBzgg@mail.gmail.com>
In-Reply-To: <20130926110818.GE6615@paksenarrion.iveqy.com>

On Thu, Sep 26, 2013 at 6:08 PM, Fredrik Gustafsson <iveqy@iveqy.com> wrote:

Show 71 quoted lines

> On Thu, Sep 26, 2013 at 05:26:27PM +0700, Duy Nguyen wrote:
>> On Thu, Sep 26, 2013 at 5:16 PM, Fredrik Gustafsson <iveqy@iveqy.com> wrote:
>> > On Tue, Sep 24, 2013 at 11:50:16AM +0200, Karsten Blees wrote:
>> >> Tests can be reproduced with 'time echo "perfhash[map] <method> 1000" | ./test-hashmap', see test-hashmap.c for definition of method flags.
>> >
>> > So I'm still curious about the actual performance improvements for git.
>> > I runned git describe on the linux kernel with both the old hashmap and
>> > this new one:
>> >
>> > ...
>> >
>> > I can't see any improvements at all here. What do I miss? Am I running
>> > git describe in the wrong way? Does linux.git have too few tags to be
>> > important?
>>
>> I wonder if it makes any difference if there are a lot more refs. I
>> hear gerrit creates a lot but don't know how many. linux-2.6 has ~350
>> refs. How about increasing the number of refs to 3500 refs?
>
> So I runned:
> for i in $(git rev-list HEAD ); do git tag "tag$i" $i ; done
>
> in my linux repo and aborted it after a while:
> iveqy@minilla:/srv/slask/linux$ git tag | wc -l
> 9323
>
> So it's a few at least. Not sure how those artificial tagnames would
> hurt or improve the performance.
>
> Old hashtable
> =============
> iveqy@minilla:/srv/slask/linux$ time ../git/git describe HEAD
> v3.12-rc2-83-g4b97280
>
> real    0m0.384s
> user    0m0.288s
> sys     0m0.092s
> iveqy@minilla:/srv/slask/linux$ time ../git/git describe HEAD
> v3.12-rc2-83-g4b97280
>
> real    0m0.383s
> user    0m0.284s
> sys     0m0.100s
> iveqy@minilla:/srv/slask/linux$ time ../git/git describe HEAD
> v3.12-rc2-83-g4b97280
>
> real    0m0.386s
> user    0m0.312s
> sys     0m0.072s
>
>
> New hashtable
> =============
> iveqy@minilla:/srv/slask/linux$ time ../git/git describe HEAD
> v3.12-rc2-83-g4b97280
>
> real    0m0.382s
> user    0m0.300s
> sys     0m0.084s
> iveqy@minilla:/srv/slask/linux$ time ../git/git describe HEAD
> v3.12-rc2-83-g4b97280
>
> real    0m0.382s
> user    0m0.288s
> sys     0m0.092s
> iveqy@minilla:/srv/slask/linux$ time ../git/git describe HEAD
> v3.12-rc2-83-g4b97280
>
> real    0m0.384s
> user    0m0.296s
> sys     0m0.088s

OK I have to say I don't see any justification for more code then.

-- 
Duy