From: Matthew Wilcox <matthew@wil.cx>
To: Liuweni <qingshenlwy@gmail.com>
Cc: linux-kernel <linux-kernel@vger.kernel.org>,
viro <viro@zeniv.linux.org.uk>, akpm <akpm@linux-foundation.org>,
jack <jack@suse.cz>, npiggin <npiggin@suse.de>,
linux-fsdevel <linux-fsdevel@vger.kernel.org>,
strongzgy <strongzgy@gmail.com>, xgr178 <xgr178@163.com>,
Liu Hui <onlyflyer@gmail.com>
Subject: Re: [PATCH 2/3]fs/inode: iunique() Optimize Performance
Date: Wed, 25 Nov 2009 07:17:28 -0700 [thread overview]
Message-ID: <20091125141727.GI9482@parisc-linux.org> (raw)
In-Reply-To: <200911252212166092236@gmail.com>
On Wed, Nov 25, 2009 at 10:12:19PM +0800, Liuweni wrote:
> @@ -605,8 +605,8 @@ static unsigned long hash(struct super_block *sb, unsigned long hashval)
> {
> unsigned long tmp;
>
> - tmp = (hashval * (unsigned long)sb) ^ (GOLDEN_RATIO_PRIME + hashval) /
> - L1_CACHE_BYTES;
> + tmp = (hashval * (unsigned long)sb) ^ (GOLDEN_RATIO_PRIME + hashval) >>
> + L1_CACHE_SHIFT;
> tmp = tmp ^ ((tmp ^ GOLDEN_RATIO_PRIME) >> I_HASHBITS);
> return tmp & I_HASHMASK;
> }
Have you compared the compiler output before/after your change? I'd be
amazed if GCC isn't able to optimise division-by-a-constant-power-of-two
into shift-by-constant.
--
Matthew Wilcox Intel Open Source Technology Centre
"Bill, look, we understand that you're interested in selling us this
operating system, but compare it to ours. We can't possibly take such
a retrograde step."
next prev parent reply other threads:[~2009-11-25 14:17 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-11-25 14:12 [PATCH 2/3]fs/inode: iunique() Optimize Performance Liuweni
2009-11-25 14:17 ` Matthew Wilcox [this message]
2009-11-25 14:45 ` Américo Wang
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