Arne Woerner wrote: --- "Jin Guojun [VFFS]" [1]<[EMAIL PROTECTED]> wrote: In you example:
Now your 1.6 GB/s reduced to 16MB/s or even worse just based on this factor. What did we show by this <<dd if=/dev/zero ...>> test? I thought that would prove the memory bandwidth is about 8Gbit/sec (1GByte/sec; 2 * <dd's bytes/sec number>/2^30). It depends on how you use /dev/zero. dd of=/dev/null if=/dev/zero bs=4k count=100k tests cache speed dd of=/dev/null if=/dev/zero bs=4m count=100 tests memory bandwidth if your cache is less than 2 MB Now you may give me the real memory bandwidth on your system :-) I would expect something around 500. Notice that your memory copy speed will be one half of it. /dev/null device really does nothing beside throwing away data. That is, it can be counted as a cost for system call. -Jin References 1. mailto:[EMAIL PROTECTED] _______________________________________________ freebsd-performance@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-performance To unsubscribe, send any mail to "[EMAIL PROTECTED]"