Hello Andy I guess most of the stat/open calls are from opening shared libraries and directories. Depending on your LD_LIBRARY_PATH there could be many failed attempts to open or stat a file. For example opening libc.so I see three attempts: open("/opt/xrootd/prod/lib/libc.so.6", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory) open("/reg/g/psdm/sw/releases/dm-current/arch/x86_64-rhel7-gcc48-opt/lib/libc.so.6", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory) open("/lib64/libc.so.6", O_RDONLY|O_CLOEXEC) = 3 Also the strace didn't include the '-f' flag so not all threads are traced and therefore the reads are very low. I ran "strace -c -f" for a 24 GB file and I see: % time seconds usecs/call calls errors syscall ------ ----------- ----------- --------- --------- ---------------- 71.19 50.881974 5098 9981 1097 futex 17.94 12.818864 312655 41 1 nanosleep 9.99 7.138469 23 314920 36189 read 0.79 0.564963 14 40227 epoll_wait 0.03 0.020346 14 1479 pwrite 0.02 0.016862 6 2973 epoll_ctl 0.02 0.011628 8 1494 sendto 0.01 0.007300 456 16 munmap 0.01 0.007009 467 15 brk 0.00 0.000850 9 91 write 0.00 0.000734 56 13 6 stat 0.00 0.000572 11 50 26 open 0.00 0.000434 7 66 mmap 0.00 0.000239 6 37 close 0.00 0.000156 4 43 mprotect 0.00 0.000152 30 5 madvise 0.00 0.000103 5 21 fstat 0.00 0.000064 32 2 2 access 0.00 0.000062 7 9 socket 0.00 0.000059 15 4 tgkill 0.00 0.000053 6 9 recvmsg 0.00 0.000045 6 7 poll 0.00 0.000045 45 1 execve 0.00 0.000043 6 7 2 connect 0.00 0.000017 6 3 getsockname 0.00 0.000010 10 1 bind 0.00 0.000010 2 6 fcntl 0.00 0.000007 4 2 getsockopt 0.00 0.000006 1 8 uname 0.00 0.000004 2 2 getpeername 0.00 0.000004 1 3 geteuid 0.00 0.000004 4 1 arch_prctl 0.00 0.000002 1 2 readv 0.00 0.000001 1 1 getegid 0.00 0.000000 0 1 lseek 0.00 0.000000 0 2 rt_sigaction 0.00 0.000000 0 1 rt_sigprocmask 0.00 0.000000 0 6 clone 0.00 0.000000 0 1 readlink 0.00 0.000000 0 1 getrlimit 0.00 0.000000 0 2 getuid 0.00 0.000000 0 1 set_tid_address 0.00 0.000000 0 2 2 openat 0.00 0.000000 0 7 set_robust_list 0.00 0.000000 0 1 epoll_create1 0.00 0.000000 0 1 pipe2 ------ ----------- ----------- --------- --------- ---------------- 100.00 71.471091 371566 37325 total Cheers, Wilko On Fri, 20 Nov 2015, Andrew Hanushevsky wrote: > Yes, I also am mystified by some of the counts like: > > 0.01 0.001123 10 107 87 open > 0.00 0.000000 0 16 14 stat > > among others. Why so many opens? Why are most of the opens and stat calls > returning an error? It does seem consistent run to run. Quite strange. > > Andy > > On Fri, 20 Nov 2015, Lukasz Janyst wrote: > >> You could try to figure out which version of BSD supports socket watermarking and run a test with that. I strongly suspect that excessive returns from epoll are the cause here. Socket watermarking does not work on Linux. http://lkml.iu.edu/hypermail/linux/kernel/0412.1/0680.html >> >> --- >> Reply to this email directly or view it on GitHub: >> https://github.com/xrootd/xrootd/issues/20#issuecomment-158479186 > > > --- > Reply to this email directly or view it on GitHub: > https://github.com/xrootd/xrootd/issues/20#issuecomment-158534692 --- Reply to this email directly or view it on GitHub: https://github.com/xrootd/xrootd/issues/20#issuecomment-158559524 ######################################################################## Use REPLY-ALL to reply to list To unsubscribe from the XROOTD-DEV list, click the following link: https://listserv.slac.stanford.edu/cgi-bin/wa?SUBED1=XROOTD-DEV&A=1