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
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