config PRINTK_TIME bool "Show timing information on printks" help Selecting this option causes timing information to be included in printk output. This allows you to measure the interval between kernel operations, including bootup operations. This is useful for identifying long delays in kernel startup. config MAGIC_SYSRQ bool "Magic SysRq key" depends on !UML help If you say Y here, you will have some control over the system even if the system crashes for example during kernel debugging (e.g., you will be able to flush the buffer cache to disk, reboot the system immediately or dump some status information). This is accomplished by pressing various keys while holding SysRq (Alt+PrintScreen). It also works on a serial console (on PC hardware at least), if you send a BREAK and then within 5 seconds a command keypress. The keys are documented in <file:Documentation/sysrq.txt>. Don't say Y unless you really know what this hack does. config DEBUG_KERNEL bool "Kernel debugging" help Say Y here if you are developing drivers or trying to debug and identify kernel problems. config LOG_BUF_SHIFT int "Kernel log buffer size (16 => 64KB, 17 => 128KB)" if DEBUG_KERNEL range 12 21 default 17 if S390 default 16 if X86_NUMAQ || IA64 default 15 if SMP default 14 help Select kernel log buffer size as a power of 2. Defaults and Examples: 17 => 128 KB for S/390 16 => 64 KB for x86 NUMAQ or IA-64 15 => 32 KB for SMP 14 => 16 KB for uniprocessor 13 => 8 KB 12 => 4 KB config DETECT_SOFTLOCKUP bool "Detect Soft Lockups" depends on DEBUG_KERNEL default y help Say Y here to enable the kernel to detect "soft lockups", which are bugs that cause the kernel to loop in kernel mode for more than 10 seconds, without giving other tasks a chance to run. When a soft-lockup is detected, the kernel will print the current stack trace (which you should report), but the system will stay locked up. This feature has negligible overhead. (Note that "hard lockups" are separate type of bugs that can be detected via the NMI-watchdog, on platforms that support it.) config SCHEDSTATS bool "Collect scheduler statistics" depends on DEBUG_KERNEL && PROC_FS help If you say Y here, additional code will be inserted into the scheduler and related routines to collect statistics about scheduler behavior and provide them in /proc/schedstat. These stats may be useful for both tuning and debugging the scheduler If you aren't debugging the scheduler or trying to tune a specific application, you can say N to avoid the very slight overhead this adds. config DEBUG_SLAB bool "Debug memory allocations" depends on DEBUG_KERNEL && SLAB help Say Y here to have the kernel do limited verification on memory allocation as well as poisoning memory on free to catch use of freed memory. This can make kmalloc/kfree-intensive workloads much slower. config DEBUG_PREEMPT bool "Debug preemptible kernel" depends on DEBUG_KERNEL && PREEMPT default y help If you say Y here then the kernel will use a debug variant of the commonly used smp_processor_id() function and will print warnings if kernel code uses it in a preemption-unsafe way. Also, the kernel will detect preemption count underflows. config DEBUG_MUTEXES bool "Mutex debugging, deadlock detection" default y depends on DEBUG_KERNEL help This allows mutex semantics violations and mutex related deadlocks (lockups) to be detected and reported automatically. config DEBUG_SPINLOCK bool "Spinlock debugging" depends on DEBUG_KERNEL help Say Y here and build SMP to catch missing spinlock initialization and certain other kinds of spinlock errors commonly made. This is best used in conjunction with the NMI watchdog so that spinlock deadlocks are also debuggable. config DEBUG_SPINLOCK_SLEEP bool "Sleep-inside-spinlock checking" depends on DEBUG_KERNEL help If you say Y here, various routines which may sleep will become very noisy if they are called with a spinlock held. config DEBUG_KOBJECT bool "kobject debugging" depends on DEBUG_KERNEL help If you say Y here, some extra kobject debugging messages will be sent to the syslog. config DEBUG_HIGHMEM bool "Highmem debugging" depends on DEBUG_KERNEL && HIGHMEM help This options enables addition error checking for high memory systems. Disable for production systems. config DEBUG_BUGVERBOSE bool "Verbose BUG() reporting (adds 70K)" if DEBUG_KERNEL && EMBEDDED depends on BUG depends on ARM || ARM26 || M32R || M68K || SPARC32 || SPARC64 || X86_32 || FRV default !EMBEDDED help Say Y here to make BUG() panics output the file name and line number of the BUG call as well as the EIP and oops trace. This aids debugging but costs about 70-100K of memory. config DEBUG_INFO bool "Compile the kernel with debug info" depends on DEBUG_KERNEL help If you say Y here the resulting kernel image will include debugging info resulting in a larger kernel image. Say Y here only if you plan to debug the kernel. If unsure, say N. config DEBUG_IOREMAP bool "Enable ioremap() debugging" depends on DEBUG_KERNEL && PARISC help Enabling this option will cause the kernel to distinguish between ioremapped and physical addresses. It will print a backtrace (at most one every 10 seconds), hopefully allowing you to see which drivers need work. Fixing all these problems is a prerequisite for turning on USE_HPPA_IOREMAP. The warnings are harmless; the kernel has enough information to fix the broken drivers automatically, but we'd like to make it more efficient by not having to do that. config DEBUG_FS bool "Debug Filesystem" depends on DEBUG_KERNEL && SYSFS help debugfs is a virtual file system that kernel developers use to put debugging files into. Enable this option to be able to read and write to these files. If unsure, say N. config DEBUG_VM bool "Debug VM" depends on DEBUG_KERNEL help Enable this to turn on extended checks in the virtual-memory system that may impact performance. If unsure, say N. config FRAME_POINTER bool "Compile the kernel with frame pointers" depends on DEBUG_KERNEL && (X86 || CRIS || M68K || M68KNOMMU || FRV || UML) default y if DEBUG_INFO && UML help If you say Y here the resulting kernel image will be slightly larger and slower, but it might give very useful debugging information on some architectures or if you use external debuggers. If you don't debug the kernel, you can say N. config FORCED_INLINING bool "Force gcc to inline functions marked 'inline'" depends on DEBUG_KERNEL default y help This option determines if the kernel forces gcc to inline the functions developers have marked 'inline'. Doing so takes away freedom from gcc to do what it thinks is best, which is desirable for the gcc 3.x series of compilers. The gcc 4.x series have a rewritten inlining algorithm and disabling this option will generate a smaller kernel there. Hopefully this algorithm is so good that allowing gcc4 to make the decision can become the default in the future, until then this option is there to test gcc for this. config RCU_TORTURE_TEST tristate "torture tests for RCU" depends on DEBUG_KERNEL default n help This option provides a kernel module that runs torture tests on the RCU infrastructure. The kernel module may be built after the fact on the running kernel to be tested, if desired. Say Y here if you want RCU torture tests to start automatically at boot time (you probably don't). Say M if you want the RCU torture tests to build as a module. Say N if you are unsure.