Shane Huang wrote: > Greetings: > > This is Shane, I'm sorry to disturb you guys. > > I have some questions which are about CPU usage percentage of "dd" > process. > I'm appreciated if you can give me some help or suggestion. > > When we do some test on our motherboards, we find that in some cases, > the CPU usage percentage of "dd" is a little high when we dump data > from SATA ODD DVD disc to SATA HDD: > # dd if=/dev/cdwriter of=/root/temp.iso
You can get dd to read & write bigger chunks less often by passing the bs=size option. The optimum size will depend on the buffers between the physical media, but '1M' might be a good first try. > The CPU percentage of "dd" process sometimes is 30% to 50%, > which is higher than we expect (<= 20%), and there is no other big > program running at the same time. > If the disc in SATA ODD is CD-R instead of DVD-R, the percentage is > much smaller(<=20). That just means that dd is waiting on the CD-R more than on the DVD-R as the DVD-R is probably faster. > So my questions are: > (1) Is there an official normal range(or criteria) to the "dd" CPU > percentage? > (2) Can we say that it's abnormal if it is higher than 30% or even 50%? > (3) And what kinds of factors lead to the high CPU percentage of "dd" > and > how to decrease it? note also you can use the `time` utility to estimate how much time is spent by dd in its own userspace code, and how much is spent in the system code dd is calling. Pádraig. _______________________________________________ Bug-coreutils mailing list Bug-coreutils@gnu.org http://lists.gnu.org/mailman/listinfo/bug-coreutils