linux-kernel - Re: [PATCH 06/14] Pramfs: Include files

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Message-Id: <200906230107.43667.arnd@arndb.de>
Date:	Tue, 23 Jun 2009 01:07:42 +0200
From:	Arnd Bergmann <arnd@...db.de>
To:	Jörn Engel <joern@...fs.org>
Cc:	Chris Simmonds <chris@...t.co.uk>,
	Marco <marco.stornelli@...il.com>,
	Sam Ravnborg <sam@...nborg.org>,
	Linux FS Devel <linux-fsdevel@...r.kernel.org>,
	Linux Embedded <linux-embedded@...r.kernel.org>,
	Linux Kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 06/14] Pramfs: Include files

On Monday 22 June 2009, Jörn Engel wrote:
> Four loops doing the same increment with different data types: long,
> u64, we32 (wrong-endian) and we64.  Compile with no optimizations.
> 
> Results on my i386 notebook:
> long:     453953 us
> we32:     880273 us
> u64:      504214 us
> we64:    2259953 us
> loops: 100000000

(couldn't resist)

The we64 number is artificially high because the glibc bswap_64
implementation forces the conversion to be done on the stack.
Using __builtin_bswap64 make this look more logical, and
makes your point even stronger (on core 2, using -m32):

long:     236792 us
we32:     500827 us
u64:      265990 us
we64:     757380 us
loops: 100000000

	Arnd <><
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