[PATCH] do not save thousands of useless symbols in KALLSYMS kernels

[PATCH] do not save thousands of useless symbols in KALLSYMS kernels

[Denis Vlasenko]

[-- Attachment #1: Type: text/plain, Size: 620 bytes --]

Sample of my kernel's mostly useless symbols
(starting_with:# of symbols):

__func__: 624
__vendorstr_: 1760
__pci_fixup_PCI_: 116
__ksymtab_: 2597
__kstrtab_: 2597
__kcrctab_: 2597
__initcall_: 236
__devicestr_: 4686
__devices_: 1760
Total: 16973
Lines in System.map: 39735

Excluding them from in-kernel symbol table saves ~300kb:

   text    data     bss     dec     hex filename
4337710 1054414  259296 5651420  563bdc vmlinux.carrier1 - w/o KALLSYMS
4342068 1296046  259296 5897410  59fcc2 vmlinux - with KALLSYMS+patch
4341948 1607634  259296 6208878  5ebd6e vmlinux.carrier - with KALLSYMS
        ^^^^^^^
--
vda

[-- Attachment #2: kallsyms.c.diff --]
[-- Type: text/x-diff, Size: 1685 bytes --]

--- linux-2.6.12.org/scripts/kallsyms.c.org	Sun Jun 19 16:11:06 2005
+++ linux-2.6.12.org/scripts/kallsyms.c	Wed Aug 10 23:52:06 2005
@@ -36,7 +36,7 @@
 
 /* we use only a subset of the complete symbol table to gather the token count,
  * to speed up compression, at the expense of a little compression ratio */
-#define WORKING_SET		1024
+#define WORKING_SET		(1024*4)
 
 /* first find the best token only on the list of tokens that would profit more
  * than GOOD_BAD_THRESHOLD. Only if this list is empty go to the "bad" list.
@@ -102,11 +102,34 @@ usage(void)
  * This ignores the intensely annoying "mapping symbols" found
  * in ARM ELF files: $a, $t and $d.
  */
+/*
+__func__: 624
+__vendorstr_: 1760
+__pci_fixup_PCI_: 116
+__ksymtab_: 2597
+__kstrtab_: 2597
+__kcrctab_: 2597
+__initcall_: 236
+__devicestr_: 4686
+__devices_: 1760
+Total: 16973
+Lines in System.map: 39735
+*/
 static inline int
 is_arm_mapping_symbol(const char *str)
 {
-	return str[0] == '$' && strchr("atd", str[1])
-	       && (str[2] == '\0' || str[2] == '.');
+	return (str[0] == '$' && strchr("atd", str[1])
+	       && (str[2] == '\0' || str[2] == '.')
+	)
+	|| (0 == strncmp(str, "__ksymtab_", sizeof("__ksymtab_")-1))
+	|| (0 == strncmp(str, "__kstrtab_", sizeof("__kstrtab_")-1))
+	|| (0 == strncmp(str, "__kcrctab_", sizeof("__kcrctab_")-1))
+	|| (0 == strncmp(str, "__devices_", sizeof("__devices_")-1))
+	|| (0 == strncmp(str, "__devicestr_", sizeof("__devicestr_")-1))
+	|| (0 == strncmp(str, "__vendorstr_", sizeof("__vendorstr_")-1))
+	|| (0 == strncmp(str, "__pci_fixup_PCI_", sizeof("__pci_fixup_PCI_")-1))
+	|| (0 == strncmp(str, "__func__", sizeof("__func__")-1))
+	;
 }
 
 static int

Re: [PATCH] do not save thousands of useless symbols in KALLSYMS kernels

[Paulo Marques]

Denis Vlasenko wrote:
> Sample of my kernel's mostly useless symbols
> (starting_with:# of symbols):
> 
> __func__: 624
> __vendorstr_: 1760
> __pci_fixup_PCI_: 116
> __ksymtab_: 2597
> __kstrtab_: 2597
> __kcrctab_: 2597
> __initcall_: 236
> __devicestr_: 4686
> __devices_: 1760
> Total: 16973
> Lines in System.map: 39735
> 
> Excluding them from in-kernel symbol table saves ~300kb:
> 
>    text    data     bss     dec     hex filename
> 4337710 1054414  259296 5651420  563bdc vmlinux.carrier1 - w/o KALLSYMS
> 4342068 1296046  259296 5897410  59fcc2 vmlinux - with KALLSYMS+patch
> 4341948 1607634  259296 6208878  5ebd6e vmlinux.carrier - with KALLSYMS
>         ^^^^^^^

Hummm.... these symbols should only go in if you config KALLSYMS_ALL. 
Are you sure your configuration doesn't have KALLSYMS_ALL enabled?

If it does, it seems like the correct behavior to include all symbols if 
you specified that you wanted _all_ symbols :)

By the way, there is a completely different version of 
scripts/kallsyms.c in -mm that you might want to look at. It will 
probably go in after 2.6.13 is out.

-- 
Paulo Marques - www.grupopie.com

It is a mistake to think you can solve any major problems
just with potatoes.
Douglas Adams

Re: [PATCH] do not save thousands of useless symbols in KALLSYMS kernels

[Denis Vlasenko]

On Thursday 11 August 2005 14:16, Paulo Marques wrote:
> Denis Vlasenko wrote:
> > Sample of my kernel's mostly useless symbols
> > (starting_with:# of symbols):
> > 
> > __func__: 624
> > __vendorstr_: 1760
> > __pci_fixup_PCI_: 116
> > __ksymtab_: 2597
> > __kstrtab_: 2597
> > __kcrctab_: 2597
> > __initcall_: 236
> > __devicestr_: 4686
> > __devices_: 1760
> > Total: 16973
> > Lines in System.map: 39735
> > 
> > Excluding them from in-kernel symbol table saves ~300kb:
> > 
> >    text    data     bss     dec     hex filename
> > 4337710 1054414  259296 5651420  563bdc vmlinux.carrier1 - w/o KALLSYMS
> > 4342068 1296046  259296 5897410  59fcc2 vmlinux - with KALLSYMS+patch
> > 4341948 1607634  259296 6208878  5ebd6e vmlinux.carrier - with KALLSYMS
> >         ^^^^^^^
> 
> Hummm.... these symbols should only go in if you config KALLSYMS_ALL. 
> Are you sure your configuration doesn't have KALLSYMS_ALL enabled?

Yes, it has...
--
vda