This changes the SHM log format, it doesn’t use 0-bytes to separate
entries anymore. Instead of using lots of printf() calls in i3-dump-log,
we now do precisely one big write().
So, to be clear: i3-dump-log and i3 both need to be upgraded.
Mismatching versions will lead to garbage output (no crashes of i3, just
garbage output).
The -f flag uses an inter-process pthread_cond_t in the shared memory
header to broadcast the arrival of new messages to all i3-dump-log
processes. This internally uses futexes and thus doesn’t even mean a
kernel call in most cases. inter-process pthread_cond_ts require NPTL
(the Native Posix Thread Library, introduce in Linux 2.6).
Compilers store the path with which they were called in the debug
symbols. Therefore, this will make backtraces show something like
../i3-4.2/src/main.c instead of src/main.c.
See also http://stackoverflow.com/questions/6473561/
before:
$ time CC=clang make -j16
CC=clang make -j16 6,04s user 0,86s system 468% cpu 1,471 total
CC=clang make -j16 6,05s user 0,87s system 468% cpu 1,477 total
CC=clang make -j16 6,15s user 0,86s system 464% cpu 1,510 total
CC=clang make -j16 6,05s user 0,93s system 467% cpu 1,493 total
CC=clang make -j16 6,10s user 0,84s system 461% cpu 1,507 total
$ time CC=gcc make -j16
CC=gcc make -j16 9,91s user 1,43s system 508% cpu 2,231 total
CC=gcc make -j16 10,02s user 1,37s system 500% cpu 2,275 total
CC=gcc make -j16 9,80s user 1,60s system 507% cpu 2,245 total
CC=gcc make -j16 10,02s user 1,44s system 506% cpu 2,264 total
CC=gcc make -j16 9,99s user 1,45s system 505% cpu 2,261 total
after:
$ time CC=clang make -j16
CC=clang make -j16 3,41s user 0,83s system 375% cpu 1,131 total
CC=clang make -j16 3,29s user 0,90s system 373% cpu 1,122 total
CC=clang make -j16 3,35s user 0,77s system 369% cpu 1,116 total
CC=clang make -j16 3,36s user 0,78s system 374% cpu 1,105 total
CC=clang make -j16 3,46s user 0,75s system 373% cpu 1,126 total
$ time CC=gcc make -j16
CC=gcc make -j16 10,74s user 1,44s system 494% cpu 2,462 total
CC=gcc make -j16 10,68s user 1,54s system 497% cpu 2,453 total
CC=gcc make -j16 10,60s user 1,60s system 488% cpu 2,499 total
CC=gcc make -j16 10,63s user 1,51s system 485% cpu 2,502 total
CC=gcc make -j16 10,70s user 1,51s system 497% cpu 2,453 total
Therefore, we enable pre-compiled headers only when CC=clang.
CPPFLGES, CFLAGS and LDFLAGS should be user variables
We now provide default flags but use I3_*FLAGS flags for our own needed
flags
Also reoder lib flags a bit
Michael Stapelberg