Re: [bigmem-patch] 4GB with Linux on IA32

Andrea Arcangeli
1999-08-16T17:19:46Z

On Mon, 16 Aug 1999, Matthew Wilcox wrote:

>Have you got some lmbench results to back this up?

Does lmbench benchmark the _allocation_ of the memory? If so could you
point out to me the exact lmbench command? (you would save me the time for
writing such a simple bench ;). I looked a bit at lmbench and it seems to
me that all mm tools are measuring the time _after_ the allocation
happened (so measuring the hardware bus/cache speed or page-colouring
algorithms and not the OS anonymous/shm page-fault time). But maybe I am
overlooking something?

All bw_mem_rw/bw_mem_cp/bw_mem_rd are _useless_ to benchmark the bigmem
patch since as just said once the allocation of memory is completed the
performance decrease will be _zero_ and not only close to zero.

The only tiny performance hit will happens while allocating a page for
clearing it or for doing the COW inside the page-fault handler (if you
are going to benchmark it make sure to #undef KMAP_DEBUG).

Andrea