Futex system calls taking too much time
Issue
- System call Futex is taking more time
- I am running strace command on a process
$ strace -c -f -p 8946
and following is the output:
% time seconds usecs/call calls errors syscall
------ ----------- ----------- --------- --------- ----------------
63.24 139.771752 1247962 112 select
32.80 72.485283 609120 119 27 futex
3.57 7.879802 3939901 2 2 restart_syscall
0.22 0.482825 0 1979137 write
0.11 0.237632 0 3951794 lseek
0.06 0.127531 797 160 fsync
0.01 0.020370 113 180 read
0.00 0.008960 149 60 20 unlink
0.00 0.002365 9 256 open
0.00 0.000251 3 100 40 rename
0.00 0.000139 1 256 close
0.00 0.000139 3 50 stat
0.00 0.000100 3 40 munmap
0.00 0.000036 0 80 ftruncate
0.00 0.000000 0 80 fstat
0.00 0.000000 0 41 mmap
0.00 0.000000 0 1 mprotect
0.00 0.000000 0 5 madvise
0.00 0.000000 0 5 clone
0.00 0.000000 0 8 fcntl
0.00 0.000000 0 64 getdents
0.00 0.000000 0 5 set_robust_list
------ ----------- ----------- --------- --------- ----------------
100.00 221.017185 5932555 89 total
Futex system call is taking alomst 33% of time. We do not expect futex takes this much time.
Environment
- Redhat Enterprise Linux
- futex() system call
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