ERROR: failed to ptrace(PEEKDATA) pid 17402: Input/output error (5)

You may found this error from your php-fpm and the php-fpm crash

tail /var/log/php-fpm/error.log
[15-May-2016 12:24:13] ERROR: failed to ptrace(PEEKDATA) pid 17402: Input/output error (5)
[15-May-2016 12:24:13] ERROR: failed to ptrace(PEEKDATA) pid 17777: Input/output error (5)
[15-May-2016 12:24:13] ERROR: failed to ptrace(PEEKDATA) pid 18886: Input/output error (5)
[15-May-2016 12:25:53] ERROR: failed to ptrace(PEEKDATA) pid 17232: Input/output error (5)
[15-May-2016 12:29:13] ERROR: failed to ptrace(PEEKDATA) pid 12091: Input/output error (5)
[15-May-2016 12:29:13] ERROR: failed to ptrace(PEEKDATA) pid 16704: Input/output error (5)
[15-May-2016 12:29:13] ERROR: failed to ptrace(PEEKDATA) pid 17779: Input/output error (5)
[15-May-2016 12:29:13] ERROR: failed to ptrace(PEEKDATA) pid 19015: Input/output error (5)
[15-May-2016 12:30:53] ERROR: failed to ptrace(PEEKDATA) pid 20663: Input/output error (5)
[15-May-2016 12:30:53] ERROR: failed to ptrace(PEEKDATA) pid 21002: Input/output error (5)

Solution to stop ERROR: failed to ptrace(PEEKDATA)

You can just comment out the php-fpm config

vim /etc/php-fpm.d/www.conf

then comment out

;slowlog = /var/log/php-fpm/slow.log
;request_slowlog_timeout = 5s