From: Andrew Morton <akpm@osdl.org>
To: Marcelo Tosatti <marcelo.tosatti@cyclades.com>
Cc: linux-kernel@vger.kernel.org
Subject: Re: [PATCH] cacheline align pagevec structure
Date: Thu, 9 Sep 2004 15:52:26 -0700 [thread overview]
Message-ID: <20040909155226.714dc704.akpm@osdl.org> (raw)
In-Reply-To: <20040909163929.GA4484@logos.cnet>
Marcelo Tosatti <marcelo.tosatti@cyclades.com> wrote:
>
> I do not see a problem with changing pagevec to "15" page pointers either,
> Andrew, is there a special reason for that "16"? Is intentional to align
> to 64 kbytes (IO device alignment)? I dont think that matters much because
> of the elevator which sorts and merges requests anyway?
No, it was just a randomly-chosen batching factor.
The tradeoff here is between
a) lock acquisition frequency versus lock hold time (increasing the size
helps).
b) icache misses versus dcache misses. (increasing the size probably hurts).
I suspect that some benefit would be seen from making the size very small
(say, 4). And on some machines, making it larger might help.
next prev parent reply other threads:[~2004-09-09 22:48 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-09-09 16:39 [PATCH] cacheline align pagevec structure Marcelo Tosatti
2004-09-09 22:49 ` Andrew Morton
2004-09-09 21:41 ` Marcelo Tosatti
2004-09-09 23:20 ` Andrew Morton
2004-09-09 22:52 ` Andrew Morton [this message]
2004-09-09 23:09 ` William Lee Irwin III
2004-09-09 22:12 ` Marcelo Tosatti
2004-09-09 23:59 ` William Lee Irwin III
2004-09-09 23:22 ` Andrew Morton
2004-09-10 0:07 ` [pagevec] resize pagevec to O(lg(NR_CPUS)) William Lee Irwin III
2004-09-10 4:56 ` Nick Piggin
2004-09-10 4:59 ` Nick Piggin
2004-09-10 17:49 ` Marcelo Tosatti
2004-09-12 0:29 ` Nick Piggin
2004-09-12 5:23 ` William Lee Irwin III
2004-09-12 4:36 ` Nick Piggin
2004-09-12 4:56 ` William Lee Irwin III
2004-09-12 4:28 ` Nick Piggin
2004-09-12 6:27 ` William Lee Irwin III
2004-09-12 6:03 ` Nick Piggin
2004-09-12 7:19 ` William Lee Irwin III
2004-09-12 7:42 ` Andrew Morton
2004-09-14 2:18 ` William Lee Irwin III
2004-09-14 2:57 ` Andrew Morton
2004-09-14 3:12 ` William Lee Irwin III
2004-09-12 8:57 ` William Lee Irwin III
2004-09-13 22:21 ` Marcelo Tosatti
2004-09-14 1:59 ` Nick Piggin
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