interpreting q(top) load average

Background — my linux host became unresponsive.

discover cpu count ] my machine #lscpu is how I found out cpu count.

top -n 1

Load average was 45, on sixteen CPU’s. It works out to be almost 300% loaded. After I killed top 5 processes, load average dropped to 13 and system became much faster:) …. one of my most successful performance fix stories.

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perl regex modifier /m /s clarified

  1. By default, q($) + q(^) won’t match newline. /m targets q($) and q(^)
  2. By default, the dot q(.) won’t match newline. /s targets the dot.
  3. The /m and /s both help get newlines matched, in different contexts.

Official doc says:

  1. /m  Treat the string being matched against as multiple lines. That is, change "^" and "$" from matching the start of the string’s first line and the end of its last line to matching embedded start and end of each line within the string.
  2. /s  Treat the string as single line. That is, change "." to match any character whatsoever, even a newline, which normally it would not match.
  3. Used together, as /ms, they let the "." match any character whatsoever, while still allowing "^" and "$" to match, respectively, just after and just before newlines within the string.

bash: split long command to multiple lines

I managed to split a huge g++ command line  to about 300 lines… much more readable.

The trick:

  • terminate each line with a space, a backslash and … NO trailing space
  • my perl one-liner must user four backslashes to insert that single backslash, then another \n
  • total there are 5 backslashes in a row.

Here’s the command

perl -pe "s/ -/ \\\\\n-/g" build1file.sh