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NAME

       tlb - TLB size and latency benchmark

SYNOPSIS

       tlb [ -L <line size> ] [ -M <len> ] [ -W <warmups> ] [ -N <repetitions>
       ]

DESCRIPTION

       tlb tries to determine the size, in pages, of  the  TLB.   The  largest
       amount of memory it will examine is len bytes.

       tlb  compares the memory latency for two different pointer chains.  The
       two chains occupy the same amount of cache space, but they  stress  the
       memory  subsystem  differently.   The first chain accesses one word per
       page, while the second chain randomly jumps through all the lines on  a
       page  before jumping to the next page.  When all of the pointers reside
       in the cache (which is the usual case), and all of the  pages  for  the
       first chain reside in the TLB, then the average memory latencies should
       be identical.  Assuming there is a fixed size TLB, then at  some  point
       the  number of pages accessed by the first page will be larger than the
       TLB.  At this point the average latency for each memory access for  the
       first chain will be a cache hit plus some fraction of a TLB miss.

       Once  the  TLB  boundary is located tlb reports the TLB miss latency as
       the TLB latency for twice as many pages as the TLB can hold.

BUGS

       tlb is an experimental benchmark, but it seems to  work  well  on  most
       systems.   However,  if  a processor has a TLB hierarchy tlb only finds
       the top level TLB.

SEE ALSO

       lmbench(8), line(8), cache(8), par_mem(8).

AUTHOR

       Carl Staelin and Larry McVoy

       Comments, suggestions, and bug reports are always welcome.

(c)2000 Carl Staelin and Larry McVoy$Date$                              TLB(8)