From: Pekka Enberg <penberg@cs.helsinki.fi>
To: kusmabite@gmail.com
Cc: "Ingo Molnar" <mingo@elte.hu>,
"Junio C Hamano" <gitster@pobox.com>,
git@vger.kernel.org, "H. Peter Anvin" <hpa@zytor.com>,
"Thomas Gleixner" <tglx@linutronix.de>,
"Peter Zijlstra" <a.p.zijlstra@chello.nl>,
"Arnaldo Carvalho de Melo" <acme@redhat.com>,
"Frédéric Weisbecker" <fweisbec@gmail.com>
Subject: Re: [PATCH] git gc: Speed it up by 18% via faster hash comparisons
Date: Thu, 28 Apr 2011 15:12:13 +0300 [thread overview]
Message-ID: <4DB9599D.3010208@cs.helsinki.fi> (raw)
In-Reply-To: <BANLkTik-uk-mpdHZxcz8Nem=nEzED_tuJg@mail.gmail.com>
On 4/28/11 2:59 PM, Erik Faye-Lund wrote:
> So my preference is still something like this. Call me conservative ;)
>
> diff --git a/cache.h b/cache.h
> index c730c58..8bc03c6 100644
> --- a/cache.h
> +++ b/cache.h
> @@ -681,13 +681,17 @@ extern char *sha1_pack_name(const unsigned char *sha1);
> extern char *sha1_pack_index_name(const unsigned char *sha1);
> extern const char *find_unique_abbrev(const unsigned char *sha1, int);
> extern const unsigned char null_sha1[20];
> -static inline int is_null_sha1(const unsigned char *sha1)
> +static inline int hashcmp(const unsigned char *sha1, const unsigned char *sha2)
> {
> - return !memcmp(sha1, null_sha1, 20);
> + /* early out for fast mis-match */
> + if (*sha1 != *sha2)
> + return *sha1 - *sha2;
> +
> + return memcmp(sha1 + 1, sha2 + 1, 19);
> }
> -static inline int hashcmp(const unsigned char *sha1, const unsigned char *sha2)
> +static inline int is_null_sha1(const unsigned char *sha1)
> {
> - return memcmp(sha1, sha2, 20);
> + return !hashcmp(sha1, null_sha1);
> }
> static inline void hashcpy(unsigned char *sha_dst, const unsigned
> char *sha_src)
> {
Yup, might be the most reasonable thing to do if it still speeds things up.
Pekka
next prev parent reply other threads:[~2011-04-28 12:12 UTC|newest]
Thread overview: 45+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-04-27 22:51 [PATCH] git gc: Speed it up by 18% via faster hash comparisons Ingo Molnar
2011-04-27 23:10 ` Ingo Molnar
2011-04-27 23:18 ` Jonathan Nieder
2011-04-28 6:36 ` Ingo Molnar
2011-04-28 9:31 ` Jonathan Nieder
2011-04-28 10:36 ` Ingo Molnar
2011-04-28 9:32 ` Dmitry Potapov
2011-04-27 23:32 ` Junio C Hamano
2011-04-28 0:35 ` Ralf Baechle
2011-04-28 8:18 ` Bernhard R. Link
2011-04-28 9:42 ` Andreas Ericsson
2011-04-28 9:55 ` Erik Faye-Lund
2011-04-28 20:19 ` H. Peter Anvin
2011-04-28 6:27 ` Ingo Molnar
2011-04-28 9:17 ` Erik Faye-Lund
2011-04-28 9:33 ` Ingo Molnar
2011-04-28 9:37 ` Ingo Molnar
2011-04-28 9:50 ` Erik Faye-Lund
2011-04-28 10:10 ` Pekka Enberg
2011-04-28 10:19 ` Erik Faye-Lund
2011-04-28 10:30 ` Pekka Enberg
2011-04-28 11:59 ` Erik Faye-Lund
2011-04-28 12:12 ` Pekka Enberg [this message]
2011-04-28 12:36 ` Jonathan Nieder
2011-04-28 12:40 ` Erik Faye-Lund
2011-04-28 13:37 ` Ingo Molnar
2011-04-28 15:14 ` Ingo Molnar
2011-04-28 16:00 ` Erik Faye-Lund
2011-04-28 20:32 ` Ingo Molnar
2011-04-29 7:05 ` Alex Riesen
2011-04-29 16:24 ` H. Peter Anvin
2011-04-28 12:16 ` Tor Arntsen
2011-04-28 20:23 ` H. Peter Anvin
2011-04-28 12:17 ` Andreas Ericsson
2011-04-28 12:28 ` Erik Faye-Lund
2011-04-28 10:19 ` Ingo Molnar
2011-04-28 12:02 ` Nguyen Thai Ngoc Duy
2011-04-28 12:18 ` Erik Faye-Lund
2011-04-28 20:20 ` Junio C Hamano
2011-04-28 16:36 ` Dmitry Potapov
2011-04-28 8:52 ` Dmitry Potapov
2011-04-28 9:11 ` Ingo Molnar
2011-04-28 9:31 ` Dmitry Potapov
2011-04-28 9:44 ` Ingo Molnar
2011-04-28 9:38 ` Ingo Molnar
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