Messages in this thread Patch in this message | | | Date | Mon, 9 Jan 2006 10:36:33 +0100 | From | Ingo Molnar <> | Subject | [patch] make CONFIG_SECCOMP default=n |
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i was profiling the scheduler on x86 and noticed some overhead related to SECCOMP, and indeed, SECCOMP runs disable_tsc() at _every_ context-switch:
if (unlikely(prev->io_bitmap_ptr || next->io_bitmap_ptr)) handle_io_bitmap(next, tss);
disable_tsc(prev_p, next_p);
return prev_p;
these are a couple of instructions in the hottest scheduler codepath!
x86_64 already removed disable_tsc() from switch_to(), but i think the right solution is to turn SECCOMP off by default.
besides the runtime overhead, there are a couple of other reasons as well why this should be done:
- CONFIG_SECCOMP=y adds 836 bytes of bloat to the kernel:
text data bss dec hex filename 4185360 867112 391012 5443484 530f9c vmlinux-noseccomp 4185992 867316 391012 5444320 5312e0 vmlinux-seccomp
- virtually nobody seems to be using it (but cpushare.com, which seems pretty inactive)
- users/distributions can still turn it on if they want it
- http://www.cpushare.com/legal seems to suggest that it is pursuing a software patent to utilize the seccomp concept in a distributed environment, and seems to give a promise that 'end users' will not be affected by that patent. How about non-end-users [i.e. server-side]? Has the Linux kernel become a vehicle for a propriety server-side feature, with every Linux user paying the price of it?
so the patch below just does the minimal common-sense change: turn it off by default.
Ingo
--
turn SECCOMP off by default - it adds runtime per-context-switch overhead on x86, and bloats the kernel.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
---- arch/i386/Kconfig | 2 +- arch/mips/Kconfig | 2 +- arch/powerpc/Kconfig | 2 +- arch/ppc/Kconfig | 2 +- arch/sparc64/Kconfig | 2 +- arch/x86_64/Kconfig | 2 +- 6 files changed, 6 insertions(+), 6 deletions(-)
Index: linux/arch/i386/Kconfig =================================================================== --- linux.orig/arch/i386/Kconfig +++ linux/arch/i386/Kconfig @@ -637,7 +637,7 @@ config REGPARM config SECCOMP bool "Enable seccomp to safely compute untrusted bytecode" depends on PROC_FS - default y + default n help This kernel feature is useful for number crunching applications that may need to compute untrusted bytecode during their Index: linux/arch/mips/Kconfig =================================================================== --- linux.orig/arch/mips/Kconfig +++ linux/arch/mips/Kconfig @@ -1787,7 +1787,7 @@ config BINFMT_ELF32 config SECCOMP bool "Enable seccomp to safely compute untrusted bytecode" depends on PROC_FS && BROKEN - default y + default n help This kernel feature is useful for number crunching applications that may need to compute untrusted bytecode during their Index: linux/arch/powerpc/Kconfig =================================================================== --- linux.orig/arch/powerpc/Kconfig +++ linux/arch/powerpc/Kconfig @@ -666,7 +666,7 @@ endif config SECCOMP bool "Enable seccomp to safely compute untrusted bytecode" depends on PROC_FS - default y + default n help This kernel feature is useful for number crunching applications that may need to compute untrusted bytecode during their Index: linux/arch/ppc/Kconfig =================================================================== --- linux.orig/arch/ppc/Kconfig +++ linux/arch/ppc/Kconfig @@ -1127,7 +1127,7 @@ endif config SECCOMP bool "Enable seccomp to safely compute untrusted bytecode" depends on PROC_FS - default y + default n help This kernel feature is useful for number crunching applications that may need to compute untrusted bytecode during their Index: linux/arch/sparc64/Kconfig =================================================================== --- linux.orig/arch/sparc64/Kconfig +++ linux/arch/sparc64/Kconfig @@ -64,7 +64,7 @@ endchoice config SECCOMP bool "Enable seccomp to safely compute untrusted bytecode" depends on PROC_FS - default y + default n help This kernel feature is useful for number crunching applications that may need to compute untrusted bytecode during their Index: linux/arch/x86_64/Kconfig =================================================================== --- linux.orig/arch/x86_64/Kconfig +++ linux/arch/x86_64/Kconfig @@ -466,7 +466,7 @@ config PHYSICAL_START config SECCOMP bool "Enable seccomp to safely compute untrusted bytecode" depends on PROC_FS - default y + default n help This kernel feature is useful for number crunching applications that may need to compute untrusted bytecode during their - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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