From: Arjan van de Ven <arjan@infradead.org>
To: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: Linux Kernel Mailing List <Linux-Kernel@vger.kernel.org>
Subject: Re: [patch 2/14] mm: pte prefetch
Date: Sun, 06 Nov 2005 09:35:01 +0100 [thread overview]
Message-ID: <1131266102.2826.3.camel@laptopd505.fenrus.org> (raw)
In-Reply-To: <436DBCE2.4050502@yahoo.com.au>
On Sun, 2005-11-06 at 19:20 +1100, Nick Piggin wrote:
> 2/14
>
> plain text document attachment (mm-pte-prefetch.patch)
> Prefetch ptes a line ahead. Worth 25% on ia64 when doing big forks.
>
> Index: linux-2.6/include/asm-generic/pgtable.h
> ===================================================================
> --- linux-2.6.orig/include/asm-generic/pgtable.h
> +++ linux-2.6/include/asm-generic/pgtable.h
> @@ -196,6 +196,33 @@ static inline void ptep_set_wrprotect(st
> })
> #endif
>
> +#ifndef __HAVE_ARCH_PTE_PREFETCH
> +#define PTES_PER_LINE (L1_CACHE_BYTES / sizeof(pte_t))
> +#define PTE_LINE_MASK (~(PTES_PER_LINE - 1))
> +#define ADDR_PER_LINE (PTES_PER_LINE << PAGE_SHIFT)
> +#define ADDR_LINE_MASK (~(ADDR_PER_LINE - 1))
> +
> +#define pte_prefetch(pte, addr, end) \
> +({ \
> + unsigned long __nextline = ((addr) + ADDR_PER_LINE) & ADDR_LINE_MASK; \
> + if (__nextline < (end)) \
> + prefetch(pte + PTES_PER_LINE); \
> +})
> +
are you sure this is right? at least on pc's having a branch predictor
miss is very expensive and might well be more expensive than the gain
you get from a prefetch
next prev parent reply other threads:[~2005-11-06 8:35 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2005-11-06 8:11 [rfc][patch 0/14] mm: performance improvements Nick Piggin
2005-11-06 8:20 ` [patch 1/14] mm: opt rmqueue Nick Piggin
2005-11-06 8:20 ` [patch 2/14] mm: Nick Piggin
2005-11-06 8:20 ` [patch 2/14] mm: pte prefetch Nick Piggin
2005-11-06 8:21 ` [patch 3/14] mm: release opt Nick Piggin
2005-11-06 8:22 ` [patch 4/14] mm: rmap opt Nick Piggin
2005-11-06 8:23 ` [patch 5/14] mm: set_page_refs opt Nick Piggin
2005-11-06 8:24 ` [patch 6/14] mm: microopt conditions Nick Piggin
2005-11-06 8:24 ` [patch 7/14] mm: remove bad_range Nick Piggin
2005-11-06 8:25 ` [patch 8/14] mm: remove pcp_low Nick Piggin
2005-11-06 8:25 ` [patch 9/14] mm: page_state opt Nick Piggin
2005-11-06 8:26 ` [patch 10/14] mm: single pcp list Nick Piggin
2005-11-06 8:26 ` [patch 11/14] mm: increase pcp size Nick Piggin
2005-11-06 8:27 ` [patch 12/14] mm: variable " Nick Piggin
2005-11-06 8:27 ` [patch 13/14] mm: cleanup zone_pcp Nick Piggin
2005-11-06 8:28 ` [patch 14/14] mm: page_alloc cleanups Nick Piggin
2005-11-13 2:38 ` [patch 9/14] mm: page_state opt Andi Kleen
2005-11-06 17:37 ` [patch 7/14] mm: remove bad_range Bob Picco
2005-11-07 0:58 ` Nick Piggin
2005-11-07 3:00 ` Bob Picco
2005-11-07 3:05 ` Nick Piggin
2005-11-07 1:40 ` [patch 5/14] mm: set_page_refs opt Christoph Hellwig
2005-11-07 1:45 ` Nick Piggin
2005-11-06 8:35 ` Arjan van de Ven [this message]
2005-11-06 8:51 ` [patch 2/14] mm: pte prefetch Nick Piggin
2005-11-06 17:37 ` [patch 1/14] mm: opt rmqueue Andi Kleen
2005-11-07 1:06 ` Nick Piggin
2005-11-07 3:23 ` Andi Kleen
2005-11-07 3:43 ` Nick Piggin
2005-11-07 1:39 ` [rfc][patch 0/14] mm: performance improvements Christoph Hellwig
2005-11-07 1:51 ` Nick Piggin
2005-11-07 3:57 ` Paul Jackson
2005-11-07 4:51 ` Nick Piggin
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