Dear all: I am so SORRY that I send the mail before I finish it, since I finger flip over the send button. SORRY~~~
i write a simple program as below to count the speed of writing a file over usb, gettimeofday before writing and gettimeofday when finish writing. but I found something make me curious. 1. my program is compiled as static and I use open, write instead of libc function calls. 2. I use the same kernel and usb modules, kernel version is 2.6.31 the only difference is I have 2 rootfs, both of them are cross-compiled as arm platform. Here comes the problem. the speed of the roofs1 I got is 8MB/s but rootfs2 is 1MB/s my concerns are: 1. my program is build as static, that means the libs in the roofs has nothing to do with this program. 2. my program is written with file I/O, instead of file operations supported by c lib, that means I direct calling kernel system call for writing data. If my assumption above are correct, that seems the kernel make me slow on rootfs2. 3. in the beginning, I thought there maybe some other program, like threads, running on rootfs2 which let my speed get slow. but how could I find them on the taret? 4. if I really want to find out whether the delay comes from kernel instead of usb or other driver module, is there configs I can open to monitor the write flow and found out where it stuck? appreciate your help, miloody -- To unsubscribe from this list: send an email with "unsubscribe kernelnewbies" to [email protected] Please read the FAQ at http://kernelnewbies.org/FAQ
