On 10/24/19 10:42 AM, Omar Sandoval wrote:
On Mon, Oct 21, 2019 at 03:57:19PM -0700, Bart Van Assche wrote:+# Configure one null_blk instance. +configure_null_blk() { + ( + cd /sys/kernel/config/nullb || return $? + ( + mkdir -p nullb0 && + cd nullb0 && + echo 0 > completion_nsec && + echo 512 > blocksize && + echo 16 > size && + echo 1 > memory_backed && + echo 1 > power + ) + ) && + ls -l /dev/nullb* &>>"$FULL"What's the point of these nested subshells? Can't this just be: configure_null_blk() { cd /sys/kernel/config/nullb && mkdir -p nullb0 && cd nullb0 && echo 0 > completion_nsec && echo 512 > blocksize && echo 16 > size && echo 1 > memory_backed && echo 1 > power && ls -l /dev/nullb* &>>"$FULL" }
The above code is not equivalent to the original code because it does not restore the original working directory.
When using 'cd' inside a subshell, the working directory that was effective before the 'cd' command is restored automatically when exiting from the subshell. I prefer using 'cd' in a subshell instead of using pushd / popd because with the former approach the old working directory is restored no matter how the exit from the subshell happens.
+modify_nr_hw_queues() { + local deadline num_cpus + + deadline=$(($(_uptime_s) + TIMEOUT)) + num_cpus=$(find /sys/devices/system/cpu -maxdepth 1 -name 'cpu[0-9]*' | + wc -l)Please just use nproc. Or even better, can you just read the original value of /sys/kernel/config/nullb/nullb0/submit_queues? Or does that start at 1?
I will have a closer look and see which alternative works best. Bart.
