open() syscall errors and friends

[gjohnson]

I am attempting to debug random slowness in an application and before I google the web too much, I thought I'd ask here:

% time     seconds  usecs/call     calls    errors syscall

------ ----------- ----------- --------- --------- ----------------

 32.37    0.027971           2     14698           epoll_wait

 29.50    0.025491           1     22815           write

 18.92    0.016346           1     29406           clock_gettime

 13.43    0.011601           1     14424           read

  4.81    0.004154          18       229           mmap

  0.36    0.000311           2       140           munmap

  0.21    0.000184           4        52         2 epoll_ctl

  0.18    0.000152           1       164        80 open

  0.12    0.000106           1       200           futex

  0.10    0.000083           1        88           close

  0.00    0.000000           0        84           fstat

  0.00    0.000000           0         4           socket

  0.00    0.000000           0         4         4 connect

  0.00    0.000000           0         8           setsockopt

  0.00    0.000000           0         4           getsockopt

  0.00    0.000000           0         4           uname

  0.00    0.000000           0         8           fcntl

  0.00    0.000000           0        20           sysinfo

------ ----------- ----------- --------- --------- ----------------

100.00    0.086399                 82352        86 total

The connect() errors stem from redis, but from what I gather a EINPROGRESS is not a bad thing...

[pid  8039] connect(53, {sa_family=AF_INET, sin_port=htons(6379), sin_addr=inet_addr("10.24.24.122")}, 16) = -1 EINPROGRESS (Operation now in progress)

These open() errors confuse me:

[pid  8032] open("/sys/devices/system/cpu/cpu0/cpufreq/cpuinfo_max_freq", O_RDONLY) = -1 ENOENT (No such file or directory)

[pid  8032] open("/sys/devices/system/cpu/cpu1/cpufreq/cpuinfo_max_freq", O_RDONLY) = -1 ENOENT (No such file or directory)

[pid  8032] open("/sys/devices/system/cpu/cpu2/cpufreq/cpuinfo_max_freq", O_RDONLY) = -1 ENOENT (No such file or directory)

[pid  8032] open("/sys/devices/system/cpu/cpu3/cpufreq/cpuinfo_max_freq", O_RDONLY) = -1 ENOENT (No such file or directory)

I was not able to capture the epoll_ctl errors...

Any thoughts? 

[Ben Noordhuis]

Try the built-in profiler, it gives you a breakdown on both JS and
C/C++ code. Make sure your program isn't idle much or you'll get
skewed results like in the strace stats you posted - that 32.37% CPU
time spent in epoll_wait is idle time.

EINPROGRESS is a benign error message, it means that the TCP handshake
is not yet complete.

The ENOENT errors is os.cpus() trying to read out the CPU status.