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SubjectRe: [PATCH] reduce export symbol CRC table size on 64-bit archs

* Jan Beulich <JBeulich@novell.com> wrote:

> Since these CRCs are really only 32-bit quantities, there's no
> need to store them in 64-bit slots. Since, however, gcc doesn't
> allow respective initializations, asm() constructs get used to
> create the CRC tables (and its for that reason that the patch only
> makes x86-64 and ia64 utilize that functionality, as I can't
> verify this doesn't break in some subtle way elsewhere).
>
> Observed size reduction (x86-64):
> - 16k kernel resident size
> - 2k module resident size
> - 1M vmlinux image size
>
> If the asm() construct could be extended to all architectures, and
> if modpost would guarantee generation of CRCs for all exported,
> then the __crc_* symbols wouldn't need to be declared weak
> anymore, could hence remain local to the exporting object. By
> adding -Wa,-strip-local-absolute to the second compilation step
> the __crc_* symbols could even be prevented from making it into
> any object file at all.
>
> Signed-off-by: Jan Beulich <jbeulich@novell.com>

>
> ---
> arch/ia64/include/asm/module.h | 2 ++
> arch/x86/include/asm/module.h | 1 +
> include/linux/module.h | 41 ++++++++++++++++++++++++++---------------
> include/linux/moduleparam.h | 10 +++++++++-
> kernel/module.c | 26 +++++++++++++-------------
> scripts/genksyms/genksyms.c | 16 ++++++++--------
> 6 files changed, 59 insertions(+), 37 deletions(-)

No objections to the (minor) x86 bits.

Ingo


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