David Ball (dball.delete@this.booksnbytes.com) on May 14, 2013 7:48 am wrote:
> One thing I'm not seeing mentioned here is anti-virus scan of files being opened
> and anti-virus scanning of the system. There's also things happening like monitoring
> programs to see if they display any malware like behavior.
>
> There are other system utilities that eat cpu time. Backup programs that do compression
> and possibly encryption. Defragment programs, many of which now have options to monitor
> new files being written and defragment them just after they're written.

Anti-virus scan and fragment should be IO-intensive rather than cpu-intensive; and
since they don't need to produce results at any particular time, in a sane system
they ought not to be using a lot of threads when other stuff is going on (and arguably
they should do nothing at all when there's real foreground work).

Encryption is a) pretty fast b) AES has hardware support in many cpu's c) is mostly
to do with stuff going to disk or network, which means the throughput is fairly low
so the average cpu load must be low.

> There's a lot of stuff running in the background that can eat
> a lot of CPU occasionally, especially during program load.
>
> Don't forget that as more security is added, more programs that talk to the internet are doing
> a lot of encryption and compression.

"Talk to the internet" usually means sending data at <10Mbit/sec. And encrypting
data at that rate doesn't impose much cpu load, even in software.