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Date:      Fri, 15 Sep 2006 09:12:52 -0400
From:      Michael Butler <imb@protected-networks.net>
To:        freebsd-current@freebsd.org
Subject:   PQ_CACHESIZE now too small?
Message-ID:  <450AA6D4.3050009@protected-networks.net>

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I note in /sys/vm/vm_page.h we have ..

/* Backward compatibility for existing PQ_*CACHE config options. */
#if !defined(PQ_CACHESIZE)
#if defined(PQ_HUGECACHE)
#define PQ_CACHESIZE 1024
#elif defined(PQ_LARGECACHE)
#define PQ_CACHESIZE 512
#elif defined(PQ_MEDIUMCACHE)
#define PQ_CACHESIZE 256
#elif defined(PQ_NORMALCACHE)
#define PQ_CACHESIZE 64
#elif defined(PQ_NOOPT)
#define PQ_CACHESIZE 0
#else
#define PQ_CACHESIZE 128
#endif
#endif                  /* !defined(PQ_CACHESIZE) */

#if PQ_CACHESIZE >= 1024
#define PQ_PRIME1 31    /* Prime number somewhat less than PQ_L2_SIZE */
#define PQ_PRIME2 23    /* Prime number somewhat less than PQ_L2_SIZE */
#define PQ_L2_SIZE 256  /* A number of colors opt for 1M cache */

#elif PQ_CACHESIZE >= 512

 [ .. snip .. ]

 .. given the ever-increasing availability of L2 cache (even my core duo
laptop has 2MB of unified cache between two cores), are these numbers
now too small?

Alternatively, are these parameters subject to the laws of diminishing
returns?

	Michael
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