From: Andi Kleen <ak@suse.de>
To: Christoph Lameter <clameter@sgi.com>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>,
Andrew Morton <akpm@osdl.org>,
linux-mm@kvack.org, Andy Whitcroft <apw@shadowen.org>,
Dave Hansen <haveblue@us.ibm.com>
Subject: Re: [PATCH] Get rid of zone_table V2
Date: Tue, 19 Sep 2006 20:24:54 +0200 [thread overview]
Message-ID: <200609192024.54477.ak@suse.de> (raw)
In-Reply-To: <Pine.LNX.4.64.0609191049250.5879@schroedinger.engr.sgi.com>
On Tuesday 19 September 2006 19:50, Christoph Lameter wrote:
> On Wed, 20 Sep 2006, Nick Piggin wrote:
>
> > BTW. I wonder why gcc isn't using two shifts in your example? Not that
> > I think it would be great even if it were, because subtle differences
> > could cause that to become more shifts...
>
> Perhaps multiply is highly optimized in contemporary processors and I am
> worrying too much about the multiply?
It is. e.g. an Opteron can do a multiply in 3-4 cycles
Just arbitary division is still slow. Division by constant is usually
also not that bad because the compiler can decompose it into multiplies
and other operations.
-Andi
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next prev parent reply other threads:[~2006-09-19 18:24 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-09-18 19:21 [PATCH] Get rid of zone_table V2 Christoph Lameter
2006-09-18 20:28 ` Andrew Morton
2006-09-18 22:51 ` Christoph Lameter
2006-09-18 23:15 ` Andrew Morton
2006-09-18 23:46 ` Christoph Lameter
2006-09-18 23:58 ` Andrew Morton
2006-09-19 0:08 ` Christoph Lameter
2006-09-19 0:14 ` Christoph Lameter
2006-09-19 0:31 ` Andrew Morton
2006-09-19 1:20 ` Christoph Lameter
2006-09-19 6:12 ` Christoph Lameter
2006-09-19 6:33 ` Andrew Morton
2006-09-19 14:10 ` Christoph Lameter
2006-09-19 15:38 ` Andrew Morton
2006-09-19 15:41 ` Christoph Lameter
2006-09-19 16:23 ` Nick Piggin
2006-09-19 16:45 ` Nick Piggin
2006-09-19 17:50 ` Christoph Lameter
2006-09-19 18:24 ` Andi Kleen [this message]
2006-09-19 16:17 ` Nick Piggin
2006-09-24 10:06 ` Andrew Morton
2006-09-24 16:58 ` Christoph Lameter
2006-09-27 9:19 ` Andrew Morton
2006-09-27 9:26 ` Andy Whitcroft
2006-09-27 11:23 ` [PATCH] zone table removal miss merge Andy Whitcroft
2006-09-27 11:23 ` Andy Whitcroft
2006-09-27 16:19 ` Christoph Lameter
2006-09-27 16:19 ` Christoph Lameter
2006-09-27 11:27 ` [PATCH] Get rid of zone_table V2 Andy Whitcroft
2006-09-27 16:24 ` Andrew Morton
2006-09-30 18:47 ` Christoph Lameter
2006-09-30 18:48 ` Christoph Lameter
2006-09-30 20:08 ` Andrew Morton
2006-10-02 15:57 ` Christoph Lameter
2006-10-02 17:10 ` Christoph Lameter
2006-10-04 10:10 ` Andy Whitcroft
2006-10-06 14:45 ` [PATCH] zoneid fix up calculations for ZONEID_PGSHIFT Andy Whitcroft
2006-10-06 17:00 ` Christoph Lameter
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