CPU負荷が高い時、kworkerの負荷が高いときなど
細かな調査ができる。
http://nishitki.hatenablog.com/entry/2017/07/12/123715
# perf top Samples: 368 of event 'cpu-clock', Event count (approx.): 71929660 Overhead Shared Object Symbol 7.18% [kernel] [k] kallsyms_expand_symbol 6.12% libc-2.12.so [.] __strstr_sse2 5.59% [kernel] [k] memcpy 5.59% perf [.] symbols__insert 5.32% libc-2.12.so [.] memchr 5.06% [kernel] [k] number 4.26% perf [.] rb_next 3.19% [kernel] [k] vsnprintf 2.93% [kernel] [k] format_decode ・ ・ ・