From: Andi Kleen <ak@suse.de>
To: Benjamin LaHaise <bcrl@linux.intel.com>
Cc: Andrew Morton <akpm@osdl.org>,
linux-mm@kvack.org, netdev@vger.kernel.org
Subject: Re: [PATCH] avoid atomic op on page free
Date: Tue, 7 Mar 2006 07:30:27 +0100 [thread overview]
Message-ID: <200603070730.27999.ak@suse.de> (raw)
In-Reply-To: <20060307015229.GJ32565@linux.intel.com>
On Tuesday 07 March 2006 02:52, Benjamin LaHaise wrote:
> Those 1-2 cycles are free if you look at how things get scheduled with the
> execution of the surrounding code. I bet $20 that you can't find a modern
> CPU where the cost is measurable (meaning something like a P4, Athlon).
> If this level of cost for the common case is a concern, it's probably worth
> making atomic_dec_and_test() inline for page_cache_release(). The overhead
> of the function call and the PageCompound() test is probably more than what
> we're talking about as you're increasing the cache footprint and actually
> performing a write to memory.
The test should be essentially free at least on an out of order CPU. Not quite sure
about in order though.
-Andi
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next prev parent reply other threads:[~2006-03-07 6:30 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-03-07 0:10 Benjamin LaHaise
2006-03-07 0:50 ` Andrew Morton
2006-03-07 1:11 ` Benjamin LaHaise
2006-03-07 1:39 ` Andrew Morton
2006-03-07 1:52 ` Benjamin LaHaise
2006-03-07 6:30 ` Andi Kleen [this message]
2006-03-07 2:04 ` Nick Piggin
2006-03-07 2:10 ` Benjamin LaHaise
2006-03-07 4:08 ` Nick Piggin
2006-03-07 2:30 ` Chen, Kenneth W
2006-03-07 4:13 ` Nick Piggin
2006-03-07 1:21 ` Rick Jones
2006-03-07 1:53 ` Nick Piggin
2006-03-07 1:58 ` Benjamin LaHaise
2006-03-07 2:14 ` Nick Piggin
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