>I'm old-school, and even I rarely use unfiltered strace anymore. Too noisy on a complex/concurrent program, and not just because of dumb stuff. I filter it down to what I'm looking for or use another tool entirely.

This!

Learning all of the strace flags is a very useful endeavor. Filtering is a must to see exactly the calls that I'm looking for.

I don't think most developers appreciate how often syscalls happen. Without filtering, you're getting all:

- file i/o (read, write, readv, writev, pread, pwrite, ...)

- network i/o (select, poll, accept, epoll, ...)

- memory allocations (mmap,munmap, sbrk, ...)

- process querying (getenv/setenv, getpid, gettid,...)

- time (gettimeofday, sleep, ...)

- synchronization (futex, ...)

I'm sure there's a bunch more that I'm neglecting. It produces quite a bit of noise!