user/sven/linux.git/kernel/cpu.c, branch v2.6.12.2

[PATCH] cputime: introduce cputime

2005-01-11T09:40:38Z

This patch introduces the concept of (virtual) cputime. Each architecture can define its method to measure cputime. The main idea is to define a cputime_t type and a set of operations on it (see asm-generic/cputime.h). Then use the type for utime, stime, cutime, cstime, it_virt_value, it_virt_incr, it_prof_value and it_prof_incr and use the cputime operations for each access to these variables. The default implementation is jiffies based and the effect of this patch for architectures which use the default implementation should be neglectible. There is a second type cputime64_t which is necessary for the kernel_stat cpu statistics. The default cputime_t is 32 bit and based on HZ, this will overflow after 49.7 days. This is not enough for kernel_stat (ihmo not enough for a processes too), so it is necessary to have a 64 bit type. The third thing that gets introduced by this patch is an additional field for the /proc/stat interface: cpu steal time. An architecture can account cpu steal time by calls to the account_stealtime function. The cpu which backs a virtual processor doesn't spent all of its time for the virtual cpu. To get meaningful cpu usage numbers this involuntary wait time needs to be accounted and exported to user space. From: Hugh Dickins The p->signal check in account_system_time is insufficient. If the timer interrupt hits near the end of exit_notify, after EXIT_ZOMBIE has been set, another cpu may release_task (NULLifying p->signal) in between account_system_time's check and check_rlimit's dereference. Nor should account_it_prof risk send_sig. But surely account_user_time is safe? Signed-off-by: Hugh Dickins Signed-off-by: Martin Schwidefsky Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

[PATCH] cpu_down() warning fix

2005-01-08T06:00:31Z

Fix (harmless?) smp_processor_id() usage in preemptible section of cpu_down. Signed-off-by: Nathan Lynch Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

[PATCH] take me home, hotplug_path[]

2004-11-01T05:06:49Z

Move hotplug_path[] out of kmod.[ch] to kobject_uevent.[ch] where it belongs now. At some time in the future we should fix the remaining bad hotplug calls (no SEQNUM, no netlink uevent): ./drivers/input/input.c (no DEVPATH on some hotplug events!) ./drivers/pnp/pnpbios/core.c ./drivers/s390/crypto/z90main.c Signed-off-by: Kay Sievers Signed-off-by: Greg Kroah-Hartman

[PATCH] remove cpu_run_sbin_hotplug()

2004-10-22T07:29:57Z

From: Keshavamurthy Anil S Remove cpu_run_sbin_hotplug() - use kobject_hotplug() instead. Signed-off-by: Anil S Keshavamurthy Signed-off-by: Andrew Morton Signed-off-by: Greg Kroah-Hartman

[PATCH] sched: hotplug add a CPU_DOWN_FAILED notifier

2004-10-18T16:10:25Z

Introduce CPU_DOWN_FAILED notifier, so we can cope with a failure after a CPU_DOWN_PREPARE notice. This fixes 3/8 "add CPU_DOWN_PREPARE notifier" to be useful Signed-off-by: Nick Piggin Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

[PATCH] sched: add CPU_DOWN_PREPARE notifier

2004-10-18T16:08:34Z

Add a CPU_DOWN_PREPARE hotplug CPU notifier. This is needed so we can dettach all sched-domains before a CPU goes down, thus we can build domains from online cpumasks, and not have to check for the possibility of a CPU coming up or going down. Signed-off-by: Nick Piggin Signed-off-by: Ingo Molnar Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

[PATCH] Add DEVPATH env variable to hotplug helper call

2004-10-03T02:51:31Z

Add $DEVPATH to the environmental variables during /sbin/hotplug call. Signed-off-by: Josef 'Jeff' Sipek Signed-off-by: Linus Torvalds

[PATCH] cpumask: make cpu_present_map real even on non-smp

2004-06-24T01:50:29Z

From: Paul Jackson This patch makes cpu_present_map a real map for all configurations, instead of a constant for non-SMP. It also moves the definition of cpu_present_map out of kernel/cpu.c into kernel/sched.c, because cpu.c isn't compiled into non-SMP kernels. The pattern is that each of the possible, present and online cpu maps are actual kernel global cpumask_t variables, for all configurations. They are documented in include/linux/cpumask.h. Some of the UP (NR_CPUS=1) code cheats, and hardcodes the assumption that the single bit position of these maps is always set, as an optimization. Signed-off-by: Paul Jackson Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

[PATCH] Revisited: ia64-cpu-hotplug-cpu_present.patch

2004-05-14T12:44:45Z

From: Paul Jackson With a hotplug capable kernel, there is a requirement to distinguish a possible CPU from one actually present. The set of possible CPU numbers doesn't change during a single system boot, but the set of present CPUs changes as CPUs are physically inserted into or removed from a system. The cpu_possible_map does not change once initialized at boot, but the cpu_present_map changes dynamically as CPUs are inserted or removed. Paul Jackson provided an expanded explanation: Ashok's cpu hot plug patch adds a cpu_present_map, resulting in the following cpu maps being available. All the following maps are fixed size bitmaps of size NR_CPUS. #ifdef CONFIG_HOTPLUG_CPU cpu_possible_map - map with all NR_CPUS bits set cpu_present_map - map with bit 'cpu' set iff cpu is populated cpu_online_map - map with bit 'cpu' set iff cpu available to scheduler #else cpu_possible_map - map with bit 'cpu' set iff cpu is populated cpu_present_map - copy of cpu_possible_map cpu_online_map - map with bit 'cpu' set iff cpu available to scheduler #endif In either case, NR_CPUS is fixed at compile time, as the static size of these bitmaps. The cpu_possible_map is fixed at boot time, as the set of CPU id's that it is possible might ever be plugged in at anytime during the life of that system boot. The cpu_present_map is dynamic(*), representing which CPUs are currently plugged in. And cpu_online_map is the dynamic subset of cpu_present_map, indicating those CPUs available for scheduling. If HOTPLUG is enabled, then cpu_possible_map is forced to have all NR_CPUS bits set, otherwise it is just the set of CPUs that ACPI reports present at boot. If HOTPLUG is enabled, then cpu_present_map varies dynamically, depending on what ACPI reports as currently plugged in, otherwise cpu_present_map is just a copy of cpu_possible_map. (*) Well, cpu_present_map is dynamic in the hotplug case. If not hotplug, it's the same as cpu_possible_map, hence fixed at boot.

[PATCH] Move migrate_all_tasks to CPU_DEAD handling

2004-05-10T06:30:01Z

From: Srivatsa Vaddagiri migrate_all_tasks is currently run with rest of the machine stopped. It iterates thr' the complete task table, turning off cpu affinity of any task that it finds affine to the dying cpu. Depending on the task table size this can take considerable time. All this time machine is stopped, doing nothing. Stopping the machine for such extended periods can be avoided if we do task migration in CPU_DEAD notification and that's precisely what this patch does. The patch puts idle task to the _front_ of the dying CPU's runqueue at the highest priority possible. This cause idle thread to run _immediately_ after kstopmachine thread yields. Idle thread notices that its cpu is offline and dies quickly. Task migration can then be done at leisure in CPU_DEAD notification, when rest of the CPUs are running. Some advantages with this approach are: - More scalable. Predicatable amout of time that machine is stopped. - No changes to hot path/core code. We are just exploiting scheduler rules which runs the next high-priority task on the runqueue. Also since I put idle task to the _front_ of the runqueue, there are no races when a equally high priority task is woken up and added to the runqueue. It gets in at the back of the runqueue, _after_ idle task! - cpu_is_offline check that is presenty required in try_to_wake_up, idle_balance and rebalance_tick can be removed, thus speeding them up a bit From: Srivatsa Vaddagiri Rusty mentioned that the unlikely hints against cpu_is_offline is redundant since the macro already has that hint. Patch below removes those redundant hints I added.