I would like to run a backup script in low CPU and disk I/O.
Is there any different between this:
#!/bin/bash ulimit -e 19 ionice -c3 -p $$ and this:
#!/bin/bash ionice -c3 -p $$ renice -n 19 -p $$ 
Add a comment |
1 Answer
There is big difference between them.
ulimit -eonly set theRLIMIT_NICE, which is a upper bound value to which the process's nice value can be set usingsetpriorityornice.renicealters the priority of running process.
Doing strace:
$ cat test.sh #!/bin/bash ulimit -e 19 Then:
$ strace ./test.sh ................................................... read(255, "#!/bin/bash\n\nulimit -e 19\n", 26) = 26 rt_sigprocmask(SIG_BLOCK, NULL, [], 8) = 0 rt_sigprocmask(SIG_BLOCK, NULL, [], 8) = 0 getrlimit(RLIMIT_NICE, {rlim_cur=0, rlim_max=0}) = 0 getrlimit(RLIMIT_NICE, {rlim_cur=0, rlim_max=0}) = 0 setrlimit(RLIMIT_NICE, {rlim_cur=19, rlim_max=19}) = 0 rt_sigprocmask(SIG_BLOCK, NULL, [], 8) = 0 read(255, "", 26) = 0 exit_group(0) You can see, ulimit only call setrlimit syscall to change the value of RLIMIT_NICE, nothing more.
Note
