From: Dave Jones <davej@redhat.com>
To: Andrew Morton <akpm@osdl.org>
Cc: davidm@hpl.hp.com, davidm@napali.hpl.hp.com, mpm@selenic.com,
linux-kernel@vger.kernel.org
Subject: Re: Fw: potential /dev/urandom scalability improvement
Date: Fri, 26 Mar 2004 11:06:19 +0000 [thread overview]
Message-ID: <20040326110619.GA25210@redhat.com> (raw)
In-Reply-To: <20040325180014.29e40b65.akpm@osdl.org>
On Thu, Mar 25, 2004 at 06:00:14PM -0800, Andrew Morton wrote:
> +static inline void prefetch_range(void *addr, size_t len)
> +{
> +#ifdef ARCH_HAS_PREFETCH
> + char *cp;
> + char *end = addr + len;
> +
> + for (cp = addr; cp < end; cp += PREFETCH_STRIDE)
> + prefetch(cp);
> +#endif
> +}
> +
> #endif
I think this may be dangerous on some CPUs, if may prefetch past
the end of the buffer. Ie, if PREFETCH_STRIDE was 32, and len
was 65, we'd end up prefetching 65->97. As well as being
wasteful to cachelines, this can crash if theres for eg
nothing mapped after the next page boundary.
Dave
next prev parent reply other threads:[~2004-03-26 11:13 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20040325141923.7080c6f0.akpm@osdl.org>
2004-03-25 22:47 ` Fw: potential /dev/urandom scalability improvement Matt Mackall
2004-03-26 1:45 ` David Mosberger
2004-03-26 2:00 ` Andrew Morton
2004-03-26 2:10 ` David Mosberger
2004-03-26 4:07 ` Matt Mackall
2004-03-26 4:19 ` Matt Mackall
2004-03-26 4:51 ` David Mosberger
2004-03-26 5:15 ` Matt Mackall
2004-03-26 5:24 ` David Mosberger
2004-03-26 11:06 ` Dave Jones [this message]
2004-03-26 18:08 ` David Mosberger
2004-03-26 18:23 ` Dave Jones
2004-03-26 21:31 ` David Mosberger
2004-03-26 18:49 ` Andrew Morton
2004-03-26 20:25 ` David Mosberger
2004-03-26 20:33 ` Andrew Morton
2004-03-26 20:45 ` Arjan van de Ven
2004-03-26 21:17 ` Andrew Morton
2004-03-27 7:44 ` Arjan van de Ven
2004-03-26 21:12 ` David Mosberger
[not found] <1DLZM-8aK-67@gated-at.bofh.it>
[not found] ` <1DLZM-8aK-65@gated-at.bofh.it>
[not found] ` <1DOE1-20o-17@gated-at.bofh.it>
[not found] ` <1DOXn-2k7-5@gated-at.bofh.it>
[not found] ` <1DXxI-Z7-39@gated-at.bofh.it>
[not found] ` <1E467-6KK-17@gated-at.bofh.it>
[not found] ` <1E4IT-7f3-21@gated-at.bofh.it>
2004-03-27 1:29 ` Andi Kleen
2004-03-27 15:48 ` Matt Mackall
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