Re: Fw: potential /dev/urandom scalability improvement

[Dave Jones]

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

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