Make fixes and improvements

- Document more compiler flags
- Expose new __print_maps() api
- Better overflow checking in mmap()
- Improve the shell example somewhat
- Fix minor runtime bugs regarding stacks
- Make kill() on fork()+execve()'d children work
- Support CLONE_CHILD_CLEARTID for proper joining
- Fix recent possible deadlock regression with --ftrace

examples/decompress.c

@@ -14,10 +14,33 @@
 #include "libc/stdio/stdio.h"
 #include "third_party/zlib/zlib.h"
 
-#define CHUNK 4096
+#define CHUNK 32768
 
 // clang-format off
 // make -j8 o//examples && dd if=/dev/urandom count=100 | tee a | o//examples/compress.com | o//examples/decompress.com >b && sha1sum a b
+/*
+# data file is o/dbg/third_party/python/python.com
+# level 0 147517 compress 495 MB/s decompress 1.4 GB/s
+# level 1 80274 compress 29.2 MB/s decompress 303 MB/s
+# level 2 79384 compress 33.8 MB/s decompress 212 MB/s
+# level 3 78875 compress 28.9 MB/s decompress 224 MB/s
+# level 4 78010 compress 27.1 MB/s decompress 319 MB/s <-- sweet spot?
+# level 5 77107 compress 19.5 MB/s decompress 273 MB/s
+# level 6 75081 compress 10.0 MB/s decompress 99.3 MB/s
+# level 7 75022 compress 7.5 MB/s decompress 287 MB/s
+# level 8 75016 compress 5.4 MB/s decompress 109 MB/s
+# level 9 75016 compress 5.4 MB/s decompress 344 MB/s
+m=
+make -j8 MODE=$m o/$m/examples || exit
+for level in $(seq 0 9); do
+  o/$m/examples/compress.com $level <o/dbg/third_party/python/python.com | dd count=10000 2>/tmp/info >/tmp/comp
+  compspeed=$(grep -Po '[.\d]+ \w+/s' /tmp/info)
+  o/$m/examples/decompress.com $level </tmp/comp | dd count=10000 2>/tmp/info >/dev/null
+  decompspeed=$(grep -Po '[.\d]+ \w+/s' /tmp/info)
+  size=$(o/$m/examples/compress.com $level <o/$m/examples/compress.com | wc -c)
+  echo "level $level $size compress $compspeed decompress $decompspeed"
+done
+*/
 // clang-format on
 
 int decompressor(int infd, int outfd) {