From: hugang <hugang@soulinfo.com>
To: Andrew Morton <akpm@digeo.com>, linux-kernel@vger.kernel.org
Subject: Re: [RFC][PATCH] Faster generic_fls
Date: Thu, 1 May 2003 13:33:07 +0800 [thread overview]
Message-ID: <20030501133307.158c7e10.hugang@soulinfo.com> (raw)
In-Reply-To: <20030430221129.11595e2e.akpm@digeo.com>
On Wed, 30 Apr 2003 22:11:29 -0700
Andrew Morton <akpm@digeo.com> wrote:
> nooo.. That has a big cache footprint. At the very least you should use
> a binary search. gcc will do it for you:
>
> switch (n) {
> case 0 ... 1:
> return 1;
> case 2 ... 3:
> return 2;
> case 4 ... 7:
> return 3;
> case 8 ... 15:
> return 4;
>
> etc.
It is here.
--------------------
static inline int fls_table_fls(unsigned n)
{
switch (n) {
case 0 ... 0: return 1;
case 1 ... 1: return 2;
case 2 ... 3: return 3;
case 4 ... 7: return 4;
case 8 ... 15: return 5;
case 16 ... 31: return 6;
case 32 ... 63: return 7;
case 64 ... 127: return 8;
case 128 ... 255: return 9;
case 256 ... 511: return 10;
case 512 ... 1023: return 11;
case 1024 ... 2047: return 12;
case 2048 ... 4095: return 13;
case 4096 ... 8191: return 14;
case 8192 ... 16383: return 15;
case 16384 ... 32767: return 16;
case 32768 ... 65535: return 17;
case 65536 ... 131071: return 18;
case 131072 ... 262143: return 19;
case 262144 ... 524287: return 20;
case 524288 ... 1048575: return 21;
case 1048576 ... 2097151: return 22;
case 2097152 ... 4194303: return 23;
case 4194304 ... 8388607: return 24;
case 8388608 ... 16777215: return 25;
case 16777216 ... 33554431: return 26;
case 33554432 ... 67108863: return 27;
case 67108864 ... 134217727: return 28;
case 134217728 ... 268435455: return 29;
case 268435456 ... 536870911: return 30;
case 536870912 ... 1073741823: return 31;
default:
}
return 32;
}
Now it in test, I will put log and file into
http://soulinfo.com/~hugang/kernel/
--
Hu Gang / Steve
Email : huagng@soulinfo.com, steve@soulinfo.com
GPG FinePrint: 4099 3F1D AE01 1817 68F7 D499 A6C2 C418 86C8 610E
ICQ# : 205800361
Registered Linux User : 204016
next prev parent reply other threads:[~2003-05-01 5:21 UTC|newest]
Thread overview: 65+ messages / expand[flat|nested] mbox.gz Atom feed top
2003-04-30 2:46 Daniel Phillips
2003-04-30 7:19 ` Willy Tarreau
2003-04-30 8:36 ` Aaron Lehmann
2003-04-30 8:43 ` Aaron Lehmann
2003-04-30 8:52 ` Aaron Lehmann
2003-04-30 8:51 ` P
2003-04-30 13:51 ` Daniel Phillips
2003-04-30 11:14 ` Falk Hueffner
2003-04-30 13:03 ` Daniel Phillips
2003-04-30 13:17 ` Falk Hueffner
2003-04-30 14:07 ` Daniel Phillips
2003-04-30 14:11 ` Linus Torvalds
2003-04-30 14:53 ` Falk Hueffner
2003-04-30 15:28 ` Linus Torvalds
2003-04-30 16:03 ` Falk Hueffner
2003-04-30 16:16 ` Linus Torvalds
2003-04-30 16:43 ` Falk Hueffner
2003-04-30 20:25 ` Alan Cox
2003-04-30 21:59 ` Falk Hueffner
2003-04-30 22:22 ` Alan Cox
2003-04-30 23:41 ` Linus Torvalds
2003-04-30 22:47 ` Alan Cox
2003-05-01 0:12 ` Falk Hueffner
2003-05-01 1:07 ` Linus Torvalds
2003-04-30 19:15 ` Daniel Phillips
2003-04-30 20:59 ` Willy Tarreau
2003-05-01 1:02 ` Daniel Phillips
2003-05-01 9:19 ` Willy Tarreau
2003-05-01 16:02 ` Linus Torvalds
2003-04-30 20:55 ` Andrew Morton
2003-05-01 5:03 ` hugang
2003-05-01 5:11 ` Andrew Morton
2003-05-01 5:33 ` hugang [this message]
2003-05-01 7:05 ` hugang
2003-05-01 13:52 ` Willy TARREAU
2003-05-01 14:14 ` Falk Hueffner
2003-05-01 14:26 ` Willy TARREAU
2003-05-01 14:53 ` hugang
2003-05-01 15:54 ` Thomas Schlichter
2003-05-02 0:33 ` hugang
2003-05-01 17:16 ` Willy TARREAU
2003-05-01 23:27 ` Thomas Schlichter
2003-05-02 0:10 ` Willy Tarreau
2003-05-02 0:43 ` Daniel Phillips
2003-05-02 0:54 ` Andrew Morton
2003-05-02 12:21 ` Daniel Phillips
2003-05-02 1:47 ` Thomas Schlichter
2003-05-02 13:24 ` Willy Tarreau
2003-05-02 0:13 ` Daniel Phillips
2003-05-02 0:13 ` Lincoln Dale
2003-05-01 5:16 ` hugang
2003-05-01 10:22 ` Willy TARREAU
2003-05-01 11:17 ` hugang
2003-05-01 11:45 ` Willy TARREAU
[not found] <87d6j34jad.fsf@student.uni-tuebingen.de.suse.lists.linux.kernel>
[not found] ` <Pine.LNX.4.44.0304301801210.20283-100000@home.transmeta.com.suse.lists.linux.kernel>
2003-05-01 1:46 ` Andi Kleen
2003-05-01 4:40 ` Linus Torvalds
2003-05-01 12:00 ` David S. Miller
2003-05-02 5:14 ` Linus Torvalds
2003-05-01 13:31 linux
2003-05-01 17:15 Chuck Ebbert
2003-05-02 8:50 Chuck Ebbert
2003-05-02 9:37 ` Peter Osterlund
2003-05-02 10:04 Chuck Ebbert
2003-05-02 22:55 ` David S. Miller
2003-05-03 2:21 Chuck Ebbert
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