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From: Arnaldo Carvalho de Melo <acme@kernel.org>
To: Bill Wendling <morbo@google.com>
Cc: Andrii Nakryiko <andrii.nakryiko@gmail.com>,
	dwarves@vger.kernel.org, bpf <bpf@vger.kernel.org>,
	Arnaldo Carvalho de Melo <arnaldo.melo@gmail.com>
Subject: Re: [PATCH] dwarf_loader: use a better hashing function
Date: Fri, 12 Feb 2021 09:35:14 -0300	[thread overview]
Message-ID: <20210212123514.GD1398414@kernel.org> (raw)
In-Reply-To: <CAGG=3QWADRX158cM-wMWG4Gf4NxN+bpJTnRNwesV5JPnL9-PWw@mail.gmail.com>

Em Thu, Feb 11, 2021 at 10:55:32PM -0800, Bill Wendling escreveu:
> On Thu, Feb 11, 2021 at 5:01 AM Arnaldo Carvalho de Melo
> <acme@kernel.org> wrote:
> >
> > Em Wed, Feb 10, 2021 at 05:31:48PM -0800, Andrii Nakryiko escreveu:
> > > On Wed, Feb 10, 2021 at 5:24 PM Bill Wendling <morbo@google.com> wrote:
> > > > On Wed, Feb 10, 2021 at 4:00 PM Andrii Nakryiko <andrii.nakryiko@gmail.com> wrote:
> > > > > On Wed, Feb 10, 2021 at 3:25 PM Bill Wendling <morbo@google.com> wrote:
> > > > > > This hashing function[1] produces better hash table bucket
> > > > > > distributions. The original hashing function always produced zeros in
> > > > > > the three least significant bits.
> >
> > > > > > The new hashing funciton gives a modest performance boost.
> >
> > > > > >       Original      New
> > > > > >        0:11.41       0:11.38
> > > > > >        0:11.36       0:11.34
> > > > > >        0:11.35       0:11.26
> > > > > >       -----------------------
> > > > > >   Avg: 0:11.373      0:11.327
> >
> > > > > > for a performance improvement of 0.4%.
> >
> > > > > > [1] From Numerical Recipes, 3rd Ed. 7.1.4 Random Hashes and Random Bytes
> >
> > > > > Can you please also test with the one libbpf uses internally:
> >
> > > > > return (val * 11400714819323198485llu) >> (64 - bits);
> >
> > > > > ?
> >
> > > > It's giving me a running time of ~11.11s, which is even better. Would
> > > > you like me to submit a patch?
> >
> > > faster is better, so yeah, why not? :)
> >
> > Yeah, I agree, faster is better, please make it so :-)
> >
> Your wish is my command! :-) Done.

Thanks, looking for the patch and applying!

No go think about something else to make it faster 8-)

- Arnaldo

  reply	other threads:[~2021-02-12 12:36 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-02-10 23:23 [PATCH] dwarf_loader: use a better hashing function Bill Wendling
2021-02-10 23:59 ` Andrii Nakryiko
2021-02-11  1:24   ` Bill Wendling
2021-02-11  1:31     ` Andrii Nakryiko
2021-02-11 13:01       ` Arnaldo Carvalho de Melo
2021-02-12  6:55         ` Bill Wendling
2021-02-12 12:35           ` Arnaldo Carvalho de Melo [this message]
2021-02-12  8:01 ` [PATCH v2] " Bill Wendling
2021-02-12 12:37   ` Arnaldo Carvalho de Melo
2021-02-12 12:39     ` Arnaldo Carvalho de Melo
2021-02-12 20:14     ` Bill Wendling

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