On Tue, 18 Sep 2007 17:07:49 -0400 Mathieu Desnoyers wrote: > Immediate values provide a way to use dynamic code patching to update > variables > sitting within the instruction stream. It saves caches lines normally used by > static read mostly variables. Enable it by default, but let users disable it > through the EMBEDDED menu with the "Disable immediate values" submenu entry. > > Note: Since I think that I really should let embedded systems developers using > RO memory the option to disable the immediate values, I choose to leave this > menu option there, in the EMBEDDED menu. Also, the "CONFIG_IMMEDIATE" makes > sense because we want to compile out all the immediate code when we decide not > to use optimized immediate values at all (it removes otherwise unused code). > > Signed-off-by: Mathieu Desnoyers <[EMAIL PROTECTED]> > CC: Adrian Bunk <[EMAIL PROTECTED]> > CC: Andi Kleen <[EMAIL PROTECTED]> > CC: Alexey Dobriyan <[EMAIL PROTECTED]> > CC: Christoph Hellwig <[EMAIL PROTECTED]> > --- > init/Kconfig | 21 +++++++++++++++++++++ > 1 file changed, 21 insertions(+) > > Index: linux-2.6-lttng/init/Kconfig > =================================================================== > --- linux-2.6-lttng.orig/init/Kconfig 2007-09-18 10:09:40.000000000 -0400 > +++ linux-2.6-lttng/init/Kconfig 2007-09-18 13:14:58.000000000 -0400 > @@ -407,6 +407,17 @@ config CC_OPTIMIZE_FOR_SIZE > config SYSCTL > bool > > +config IMMEDIATE > + default y if !DISABLE_IMMEDIATE
So DISABLE_IMMEDIATE is just an intermediate symbol to make this option be displayed in the EMBEDDED menu instead of in the General Setup menu ? > + depends on X86_32 || PPC || PPC64 > + bool > + help > + Immediate values are used as read-mostly variables that are rarely > + updated. They use code patching to modify the values inscribed in the > + instruction stream. It provides a way to save precious cache lines > + that would otherwise have to be used by these variables. They can be > + disabled through the EMBEDDED menu. > + > menuconfig EMBEDDED > bool "Configure standard kernel features (for small systems)" > help > @@ -646,6 +657,16 @@ config PROC_KPAGEMAP > information on page-level memory usage. Disabling this interface > will reduce the size of the kernel by around 600 bytes. > > +config DISABLE_IMMEDIATE > + default y if EMBEDDED > + bool "Disable immediate values" if EMBEDDED > + depends on X86_32 || PPC || PPC64 > + help > + Disable code patching based immediate values for embedded systems. It > + consumes slightly more memory and requires to modify the instruction > + stream each time a variable is updated. Should really be disabled for > + embedded systems with read-only text. > + > endmenu # General setup > > config RT_MUTEXES --- ~Randy *** Remember to use Documentation/SubmitChecklist when testing your code *** - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
