Subject: RE: problems regarding libc
To: TAKEMURA, Shin <takemura@netbsd.org>
From: Pai-Hsiang Hsiao <shawn@eecs.harvard.edu>
List: port-hpcmips
Date: 12/23/1999 18:23:03
> I wrote a simple program, which call bzero(1MB) 100 times and
> ran it within time command on my MC-R500. The time command 
> says it takes 6.5 sec, so I roughly got 16MB/s. Is that enough?
> 
> (MC-R500 has VR4111 of which clock is 78MHz or 100MHz.)

I don't know what's the theoretical bandwidth of both machine, could
you please try use the C version bcopy included in the libc
(libsa/string/)
and see what's the difference? It might be better for you to test
different
size of block copy, to avoid biased cache effect.

The difference here is huge (4MB/s v.s. 160MB/s), though the benchmark
(hbench-OS, a patched version of lmbench) program itself might have
problems.

My conjecture is, 16MB/s is still far from enough. If it's a 78MHz machine
with 32 bit memory bus, the memory (write/copy) bandwidth should not be
as low as 16MB/s. That's why I believe there're some problems in the library's
bzero/bcopy. FYI, Another Pentium III 350MHz under test has more than
1000MB/s memory bandwidth.

I can not reach the machine I have till Jan. 5, so I can do nothing here.

// Shawn