libbb: introduce and use strcpy_and_process_escape_sequences

[oweals/busybox.git] / docs / keep_data_small.txt

diff --git a/docs/keep_data_small.txt b/docs/keep_data_small.txt
index 15e41aefd11fd02a747f229df3d1d127842079a6..01c0d3c7b00d30caba0948430c23f3a6cac2f508 100644 (file)
--- a/docs/keep_data_small.txt
+++ b/docs/keep_data_small.txt
@@ -43,6 +43,16 @@ takes 55k of memory on 64-bit x86 kernel.
 
 On 32-bit kernel we need ~26k per applet.
 
+Script:
+
+i=1000; while test $i != 0; do
+        echo -n .
+        busybox sleep 30 &
+        i=$((i - 1))
+done
+echo
+wait
+
 (Data from NOMMU arches are sought. Provide 'size busybox' output too)
 
 
@@ -65,7 +75,7 @@ archival/libunarchive/decompress_unzip.c:
 (see the rest of the file to get the idea)
 
 This example completely eliminates globals in that module.
-Required memory is allocated in inflate_gunzip() [its main module]
+Required memory is allocated in unpack_gz_stream() [its main module]
 and then passed down to all subroutines which need to access 'globals'
 as a parameter.
 
@@ -89,9 +99,9 @@ and then declare that ptr_to_globals is a pointer to it:
 
 ptr_to_globals is declared as constant pointer.
 This helps gcc understand that it won't change, resulting in noticeably
-smaller code. In order to assign it, use PTR_TO_GLOBALS macro:
+smaller code. In order to assign it, use SET_PTR_TO_GLOBALS macro:
 
-       PTR_TO_GLOBALS = xzalloc(sizeof(G));
+       SET_PTR_TO_GLOBALS(xzalloc(sizeof(G)));
 
 Typically it is done in <applet>_main().
 
@@ -112,7 +122,7 @@ Be careful, though, and use it only if globals fit into bb_common_bufsiz1.
 Since bb_common_bufsiz1 is BUFSIZ + 1 bytes long and BUFSIZ can change
 from one libc to another, you have to add compile-time check for it:
 
-if(sizeof(struct globals) > sizeof(bb_common_bufsiz1))
+if (sizeof(struct globals) > sizeof(bb_common_bufsiz1))
        BUG_<applet>_globals_too_big();
 
 
@@ -135,6 +145,11 @@ one of above methods is not worth the resulting code obfuscation.
 If you have less than ~300 bytes of global data - don't bother.
 
 
+               Finding non-shared duplicated strings
+
+strings busybox | sort | uniq -c | sort -nr
+
+
                gcc's data alignment problem
 
 The following attribute added in vi.c:
@@ -178,5 +193,64 @@ struct {
 char vc31[31] = { 1 }; // unaligned
 char vc32[32] = { 1 }; // aligned to 32 bytes
 
--fpack-struct=1 reduces alignment of s28 to 1 (but probably will break layout
-of many libc structs) but s32 and vc32 are still aligned to 32 bytes.
+-fpack-struct=1 reduces alignment of s28 to 1 (but probably
+will break layout of many libc structs) but s32 and vc32
+are still aligned to 32 bytes.
+
+I will try to cook up a patch to add a gcc option for disabling it.
+Meanwhile, this is where it can be disabled in gcc source:
+
+gcc/config/i386/i386.c
+int
+ix86_data_alignment (tree type, int align)
+{
+#if 0
+  if (AGGREGATE_TYPE_P (type)
+       && TYPE_SIZE (type)
+       && TREE_CODE (TYPE_SIZE (type)) == INTEGER_CST
+       && (TREE_INT_CST_LOW (TYPE_SIZE (type)) >= 256
+           || TREE_INT_CST_HIGH (TYPE_SIZE (type))) && align < 256)
+    return 256;
+#endif
+
+Result (non-static busybox built against glibc):
+
+# size /usr/srcdevel/bbox/fix/busybox.t0/busybox busybox
+   text    data     bss     dec     hex filename
+ 634416    2736   23856  661008   a1610 busybox
+ 632580    2672   22944  658196   a0b14 busybox_noalign
+
+
+
+               Keeping code small
+
+Set CONFIG_EXTRA_CFLAGS="-fno-inline-functions-called-once",
+produce "make bloatcheck", see the biggest auto-inlined functions.
+Now, set CONFIG_EXTRA_CFLAGS back to "", but add NOINLINE
+to some of these functions. In 1.16.x timeframe, the results were
+(annotated "make bloatcheck" output):
+
+function             old     new   delta
+expand_vars_to_list    -    1712   +1712 win
+lzo1x_optimize         -    1429   +1429 win
+arith_apply            -    1326   +1326 win
+read_interfaces        -    1163   +1163 loss, leave w/o NOINLINE
+logdir_open            -    1148   +1148 win
+check_deps             -    1148   +1148 loss
+rewrite                -    1039   +1039 win
+run_pipe             358    1396   +1038 win
+write_status_file      -    1029   +1029 almost the same, leave w/o NOINLINE
+dump_identity          -     987    +987 win
+mainQSort3             -     921    +921 win
+parse_one_line         -     916    +916 loss
+summarize              -     897    +897 almost the same
+do_shm                 -     884    +884 win
+cpio_o                 -     863    +863 win
+subCommand             -     841    +841 loss
+receive                -     834    +834 loss
+
+855 bytes saved in total.
+
+scripts/mkdiff_obj_bloat may be useful to automate this process: run
+"scripts/mkdiff_obj_bloat NORMALLY_BUILT_TREE FORCED_NOINLINE_TREE"
+and select modules which shrank.