![David Howells](/assets/img/avatar_default.png)
Maintain a per-CPU global "struct pt_regs *" variable which can be used instead of passing regs around manually through all ~1800 interrupt handlers in the Linux kernel. The regs pointer is used in few places, but it potentially costs both stack space and code to pass it around. On the FRV arch, removing the regs parameter from all the genirq function results in a 20% speed up of the IRQ exit path (ie: from leaving timer_interrupt() to leaving do_IRQ()). Where appropriate, an arch may override the generic storage facility and do something different with the variable. On FRV, for instance, the address is maintained in GR28 at all times inside the kernel as part of general exception handling. Having looked over the code, it appears that the parameter may be handed down through up to twenty or so layers of functions. Consider a USB character device attached to a USB hub, attached to a USB controller that posts its interrupts through a cascaded auxiliary interrupt controller. A character device driver may want to pass regs to the sysrq handler through the input layer which adds another few layers of parameter passing. I've build this code with allyesconfig for x86_64 and i386. I've runtested the main part of the code on FRV and i386, though I can't test most of the drivers. I've also done partial conversion for powerpc and MIPS - these at least compile with minimal configurations. This will affect all archs. Mostly the changes should be relatively easy. Take do_IRQ(), store the regs pointer at the beginning, saving the old one: struct pt_regs *old_regs = set_irq_regs(regs); And put the old one back at the end: set_irq_regs(old_regs); Don't pass regs through to generic_handle_irq() or __do_IRQ(). In timer_interrupt(), this sort of change will be necessary: - update_process_times(user_mode(regs)); - profile_tick(CPU_PROFILING, regs); + update_process_times(user_mode(get_irq_regs())); + profile_tick(CPU_PROFILING); I'd like to move update_process_times()'s use of get_irq_regs() into itself, except that i386, alone of the archs, uses something other than user_mode(). Some notes on the interrupt handling in the drivers: (*) input_dev() is now gone entirely. The regs pointer is no longer stored in the input_dev struct. (*) finish_unlinks() in drivers/usb/host/ohci-q.c needs checking. It does something different depending on whether it's been supplied with a regs pointer or not. (*) Various IRQ handler function pointers have been moved to type irq_handler_t. Signed-Off-By: David Howells <dhowells@redhat.com> (cherry picked from 1b16e7ac850969f38b375e511e3fa2f474a33867 commit)
558 lines
15 KiB
C
558 lines
15 KiB
C
/*
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* linux/kernel/profile.c
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* Simple profiling. Manages a direct-mapped profile hit count buffer,
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* with configurable resolution, support for restricting the cpus on
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* which profiling is done, and switching between cpu time and
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* schedule() calls via kernel command line parameters passed at boot.
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*
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* Scheduler profiling support, Arjan van de Ven and Ingo Molnar,
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* Red Hat, July 2004
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* Consolidation of architecture support code for profiling,
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* William Irwin, Oracle, July 2004
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* Amortized hit count accounting via per-cpu open-addressed hashtables
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* to resolve timer interrupt livelocks, William Irwin, Oracle, 2004
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*/
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#include <linux/module.h>
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#include <linux/profile.h>
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#include <linux/bootmem.h>
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#include <linux/notifier.h>
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#include <linux/mm.h>
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#include <linux/cpumask.h>
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#include <linux/cpu.h>
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#include <linux/profile.h>
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#include <linux/highmem.h>
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#include <linux/mutex.h>
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#include <asm/sections.h>
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#include <asm/semaphore.h>
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#include <asm/irq_regs.h>
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struct profile_hit {
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u32 pc, hits;
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};
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#define PROFILE_GRPSHIFT 3
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#define PROFILE_GRPSZ (1 << PROFILE_GRPSHIFT)
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#define NR_PROFILE_HIT (PAGE_SIZE/sizeof(struct profile_hit))
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#define NR_PROFILE_GRP (NR_PROFILE_HIT/PROFILE_GRPSZ)
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/* Oprofile timer tick hook */
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int (*timer_hook)(struct pt_regs *) __read_mostly;
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static atomic_t *prof_buffer;
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static unsigned long prof_len, prof_shift;
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static int prof_on __read_mostly;
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static cpumask_t prof_cpu_mask = CPU_MASK_ALL;
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#ifdef CONFIG_SMP
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static DEFINE_PER_CPU(struct profile_hit *[2], cpu_profile_hits);
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static DEFINE_PER_CPU(int, cpu_profile_flip);
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static DEFINE_MUTEX(profile_flip_mutex);
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#endif /* CONFIG_SMP */
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static int __init profile_setup(char * str)
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{
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static char __initdata schedstr[] = "schedule";
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int par;
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if (!strncmp(str, schedstr, strlen(schedstr))) {
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prof_on = SCHED_PROFILING;
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if (str[strlen(schedstr)] == ',')
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str += strlen(schedstr) + 1;
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if (get_option(&str, &par))
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prof_shift = par;
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printk(KERN_INFO
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"kernel schedule profiling enabled (shift: %ld)\n",
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prof_shift);
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} else if (get_option(&str, &par)) {
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prof_shift = par;
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prof_on = CPU_PROFILING;
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printk(KERN_INFO "kernel profiling enabled (shift: %ld)\n",
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prof_shift);
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}
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return 1;
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}
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__setup("profile=", profile_setup);
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void __init profile_init(void)
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{
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if (!prof_on)
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return;
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/* only text is profiled */
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prof_len = (_etext - _stext) >> prof_shift;
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prof_buffer = alloc_bootmem(prof_len*sizeof(atomic_t));
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}
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/* Profile event notifications */
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#ifdef CONFIG_PROFILING
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static BLOCKING_NOTIFIER_HEAD(task_exit_notifier);
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static ATOMIC_NOTIFIER_HEAD(task_free_notifier);
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static BLOCKING_NOTIFIER_HEAD(munmap_notifier);
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void profile_task_exit(struct task_struct * task)
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{
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blocking_notifier_call_chain(&task_exit_notifier, 0, task);
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}
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int profile_handoff_task(struct task_struct * task)
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{
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int ret;
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ret = atomic_notifier_call_chain(&task_free_notifier, 0, task);
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return (ret == NOTIFY_OK) ? 1 : 0;
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}
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void profile_munmap(unsigned long addr)
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{
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blocking_notifier_call_chain(&munmap_notifier, 0, (void *)addr);
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}
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int task_handoff_register(struct notifier_block * n)
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{
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return atomic_notifier_chain_register(&task_free_notifier, n);
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}
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int task_handoff_unregister(struct notifier_block * n)
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{
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return atomic_notifier_chain_unregister(&task_free_notifier, n);
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}
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int profile_event_register(enum profile_type type, struct notifier_block * n)
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{
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int err = -EINVAL;
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switch (type) {
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case PROFILE_TASK_EXIT:
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err = blocking_notifier_chain_register(
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&task_exit_notifier, n);
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break;
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case PROFILE_MUNMAP:
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err = blocking_notifier_chain_register(
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&munmap_notifier, n);
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break;
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}
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return err;
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}
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int profile_event_unregister(enum profile_type type, struct notifier_block * n)
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{
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int err = -EINVAL;
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switch (type) {
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case PROFILE_TASK_EXIT:
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err = blocking_notifier_chain_unregister(
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&task_exit_notifier, n);
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break;
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case PROFILE_MUNMAP:
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err = blocking_notifier_chain_unregister(
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&munmap_notifier, n);
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break;
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}
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return err;
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}
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int register_timer_hook(int (*hook)(struct pt_regs *))
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{
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if (timer_hook)
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return -EBUSY;
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timer_hook = hook;
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return 0;
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}
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void unregister_timer_hook(int (*hook)(struct pt_regs *))
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{
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WARN_ON(hook != timer_hook);
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timer_hook = NULL;
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/* make sure all CPUs see the NULL hook */
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synchronize_sched(); /* Allow ongoing interrupts to complete. */
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}
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EXPORT_SYMBOL_GPL(register_timer_hook);
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EXPORT_SYMBOL_GPL(unregister_timer_hook);
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EXPORT_SYMBOL_GPL(task_handoff_register);
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EXPORT_SYMBOL_GPL(task_handoff_unregister);
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#endif /* CONFIG_PROFILING */
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EXPORT_SYMBOL_GPL(profile_event_register);
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EXPORT_SYMBOL_GPL(profile_event_unregister);
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#ifdef CONFIG_SMP
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/*
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* Each cpu has a pair of open-addressed hashtables for pending
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* profile hits. read_profile() IPI's all cpus to request them
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* to flip buffers and flushes their contents to prof_buffer itself.
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* Flip requests are serialized by the profile_flip_mutex. The sole
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* use of having a second hashtable is for avoiding cacheline
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* contention that would otherwise happen during flushes of pending
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* profile hits required for the accuracy of reported profile hits
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* and so resurrect the interrupt livelock issue.
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*
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* The open-addressed hashtables are indexed by profile buffer slot
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* and hold the number of pending hits to that profile buffer slot on
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* a cpu in an entry. When the hashtable overflows, all pending hits
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* are accounted to their corresponding profile buffer slots with
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* atomic_add() and the hashtable emptied. As numerous pending hits
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* may be accounted to a profile buffer slot in a hashtable entry,
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* this amortizes a number of atomic profile buffer increments likely
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* to be far larger than the number of entries in the hashtable,
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* particularly given that the number of distinct profile buffer
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* positions to which hits are accounted during short intervals (e.g.
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* several seconds) is usually very small. Exclusion from buffer
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* flipping is provided by interrupt disablement (note that for
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* SCHED_PROFILING profile_hit() may be called from process context).
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* The hash function is meant to be lightweight as opposed to strong,
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* and was vaguely inspired by ppc64 firmware-supported inverted
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* pagetable hash functions, but uses a full hashtable full of finite
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* collision chains, not just pairs of them.
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*
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* -- wli
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*/
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static void __profile_flip_buffers(void *unused)
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{
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int cpu = smp_processor_id();
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per_cpu(cpu_profile_flip, cpu) = !per_cpu(cpu_profile_flip, cpu);
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}
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static void profile_flip_buffers(void)
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{
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int i, j, cpu;
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mutex_lock(&profile_flip_mutex);
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j = per_cpu(cpu_profile_flip, get_cpu());
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put_cpu();
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on_each_cpu(__profile_flip_buffers, NULL, 0, 1);
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for_each_online_cpu(cpu) {
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struct profile_hit *hits = per_cpu(cpu_profile_hits, cpu)[j];
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for (i = 0; i < NR_PROFILE_HIT; ++i) {
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if (!hits[i].hits) {
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if (hits[i].pc)
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hits[i].pc = 0;
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continue;
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}
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atomic_add(hits[i].hits, &prof_buffer[hits[i].pc]);
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hits[i].hits = hits[i].pc = 0;
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}
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}
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mutex_unlock(&profile_flip_mutex);
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}
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static void profile_discard_flip_buffers(void)
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{
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int i, cpu;
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mutex_lock(&profile_flip_mutex);
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i = per_cpu(cpu_profile_flip, get_cpu());
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put_cpu();
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on_each_cpu(__profile_flip_buffers, NULL, 0, 1);
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for_each_online_cpu(cpu) {
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struct profile_hit *hits = per_cpu(cpu_profile_hits, cpu)[i];
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memset(hits, 0, NR_PROFILE_HIT*sizeof(struct profile_hit));
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}
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mutex_unlock(&profile_flip_mutex);
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}
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void profile_hit(int type, void *__pc)
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{
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unsigned long primary, secondary, flags, pc = (unsigned long)__pc;
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int i, j, cpu;
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struct profile_hit *hits;
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if (prof_on != type || !prof_buffer)
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return;
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pc = min((pc - (unsigned long)_stext) >> prof_shift, prof_len - 1);
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i = primary = (pc & (NR_PROFILE_GRP - 1)) << PROFILE_GRPSHIFT;
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secondary = (~(pc << 1) & (NR_PROFILE_GRP - 1)) << PROFILE_GRPSHIFT;
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cpu = get_cpu();
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hits = per_cpu(cpu_profile_hits, cpu)[per_cpu(cpu_profile_flip, cpu)];
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if (!hits) {
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put_cpu();
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return;
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}
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local_irq_save(flags);
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do {
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for (j = 0; j < PROFILE_GRPSZ; ++j) {
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if (hits[i + j].pc == pc) {
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hits[i + j].hits++;
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goto out;
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} else if (!hits[i + j].hits) {
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hits[i + j].pc = pc;
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hits[i + j].hits = 1;
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goto out;
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}
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}
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i = (i + secondary) & (NR_PROFILE_HIT - 1);
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} while (i != primary);
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atomic_inc(&prof_buffer[pc]);
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for (i = 0; i < NR_PROFILE_HIT; ++i) {
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atomic_add(hits[i].hits, &prof_buffer[hits[i].pc]);
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hits[i].pc = hits[i].hits = 0;
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}
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out:
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local_irq_restore(flags);
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put_cpu();
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}
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#ifdef CONFIG_HOTPLUG_CPU
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static int __devinit profile_cpu_callback(struct notifier_block *info,
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unsigned long action, void *__cpu)
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{
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int node, cpu = (unsigned long)__cpu;
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struct page *page;
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switch (action) {
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case CPU_UP_PREPARE:
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node = cpu_to_node(cpu);
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per_cpu(cpu_profile_flip, cpu) = 0;
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if (!per_cpu(cpu_profile_hits, cpu)[1]) {
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page = alloc_pages_node(node,
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GFP_KERNEL | __GFP_ZERO | GFP_THISNODE,
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0);
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if (!page)
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return NOTIFY_BAD;
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per_cpu(cpu_profile_hits, cpu)[1] = page_address(page);
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}
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if (!per_cpu(cpu_profile_hits, cpu)[0]) {
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page = alloc_pages_node(node,
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GFP_KERNEL | __GFP_ZERO | GFP_THISNODE,
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0);
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if (!page)
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goto out_free;
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per_cpu(cpu_profile_hits, cpu)[0] = page_address(page);
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}
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break;
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out_free:
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page = virt_to_page(per_cpu(cpu_profile_hits, cpu)[1]);
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per_cpu(cpu_profile_hits, cpu)[1] = NULL;
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__free_page(page);
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return NOTIFY_BAD;
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case CPU_ONLINE:
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cpu_set(cpu, prof_cpu_mask);
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break;
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case CPU_UP_CANCELED:
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case CPU_DEAD:
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cpu_clear(cpu, prof_cpu_mask);
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if (per_cpu(cpu_profile_hits, cpu)[0]) {
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page = virt_to_page(per_cpu(cpu_profile_hits, cpu)[0]);
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per_cpu(cpu_profile_hits, cpu)[0] = NULL;
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__free_page(page);
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}
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if (per_cpu(cpu_profile_hits, cpu)[1]) {
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page = virt_to_page(per_cpu(cpu_profile_hits, cpu)[1]);
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per_cpu(cpu_profile_hits, cpu)[1] = NULL;
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__free_page(page);
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}
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break;
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}
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return NOTIFY_OK;
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}
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#endif /* CONFIG_HOTPLUG_CPU */
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#else /* !CONFIG_SMP */
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#define profile_flip_buffers() do { } while (0)
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#define profile_discard_flip_buffers() do { } while (0)
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void profile_hit(int type, void *__pc)
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{
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unsigned long pc;
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if (prof_on != type || !prof_buffer)
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return;
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pc = ((unsigned long)__pc - (unsigned long)_stext) >> prof_shift;
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atomic_inc(&prof_buffer[min(pc, prof_len - 1)]);
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}
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#endif /* !CONFIG_SMP */
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void profile_tick(int type)
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{
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struct pt_regs *regs = get_irq_regs();
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if (type == CPU_PROFILING && timer_hook)
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timer_hook(regs);
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if (!user_mode(regs) && cpu_isset(smp_processor_id(), prof_cpu_mask))
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profile_hit(type, (void *)profile_pc(regs));
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}
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#ifdef CONFIG_PROC_FS
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#include <linux/proc_fs.h>
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#include <asm/uaccess.h>
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#include <asm/ptrace.h>
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static int prof_cpu_mask_read_proc (char *page, char **start, off_t off,
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int count, int *eof, void *data)
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{
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int len = cpumask_scnprintf(page, count, *(cpumask_t *)data);
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if (count - len < 2)
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return -EINVAL;
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len += sprintf(page + len, "\n");
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return len;
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}
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static int prof_cpu_mask_write_proc (struct file *file, const char __user *buffer,
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unsigned long count, void *data)
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{
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cpumask_t *mask = (cpumask_t *)data;
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unsigned long full_count = count, err;
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cpumask_t new_value;
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err = cpumask_parse(buffer, count, new_value);
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if (err)
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return err;
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*mask = new_value;
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return full_count;
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}
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void create_prof_cpu_mask(struct proc_dir_entry *root_irq_dir)
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{
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struct proc_dir_entry *entry;
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/* create /proc/irq/prof_cpu_mask */
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if (!(entry = create_proc_entry("prof_cpu_mask", 0600, root_irq_dir)))
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return;
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entry->nlink = 1;
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entry->data = (void *)&prof_cpu_mask;
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entry->read_proc = prof_cpu_mask_read_proc;
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entry->write_proc = prof_cpu_mask_write_proc;
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}
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/*
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* This function accesses profiling information. The returned data is
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* binary: the sampling step and the actual contents of the profile
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* buffer. Use of the program readprofile is recommended in order to
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* get meaningful info out of these data.
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*/
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static ssize_t
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read_profile(struct file *file, char __user *buf, size_t count, loff_t *ppos)
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{
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unsigned long p = *ppos;
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ssize_t read;
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char * pnt;
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unsigned int sample_step = 1 << prof_shift;
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profile_flip_buffers();
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if (p >= (prof_len+1)*sizeof(unsigned int))
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return 0;
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if (count > (prof_len+1)*sizeof(unsigned int) - p)
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count = (prof_len+1)*sizeof(unsigned int) - p;
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read = 0;
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while (p < sizeof(unsigned int) && count > 0) {
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put_user(*((char *)(&sample_step)+p),buf);
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buf++; p++; count--; read++;
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}
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pnt = (char *)prof_buffer + p - sizeof(atomic_t);
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if (copy_to_user(buf,(void *)pnt,count))
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return -EFAULT;
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read += count;
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*ppos += read;
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return read;
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}
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/*
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* Writing to /proc/profile resets the counters
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*
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* Writing a 'profiling multiplier' value into it also re-sets the profiling
|
|
* interrupt frequency, on architectures that support this.
|
|
*/
|
|
static ssize_t write_profile(struct file *file, const char __user *buf,
|
|
size_t count, loff_t *ppos)
|
|
{
|
|
#ifdef CONFIG_SMP
|
|
extern int setup_profiling_timer (unsigned int multiplier);
|
|
|
|
if (count == sizeof(int)) {
|
|
unsigned int multiplier;
|
|
|
|
if (copy_from_user(&multiplier, buf, sizeof(int)))
|
|
return -EFAULT;
|
|
|
|
if (setup_profiling_timer(multiplier))
|
|
return -EINVAL;
|
|
}
|
|
#endif
|
|
profile_discard_flip_buffers();
|
|
memset(prof_buffer, 0, prof_len * sizeof(atomic_t));
|
|
return count;
|
|
}
|
|
|
|
static struct file_operations proc_profile_operations = {
|
|
.read = read_profile,
|
|
.write = write_profile,
|
|
};
|
|
|
|
#ifdef CONFIG_SMP
|
|
static void __init profile_nop(void *unused)
|
|
{
|
|
}
|
|
|
|
static int __init create_hash_tables(void)
|
|
{
|
|
int cpu;
|
|
|
|
for_each_online_cpu(cpu) {
|
|
int node = cpu_to_node(cpu);
|
|
struct page *page;
|
|
|
|
page = alloc_pages_node(node,
|
|
GFP_KERNEL | __GFP_ZERO | GFP_THISNODE,
|
|
0);
|
|
if (!page)
|
|
goto out_cleanup;
|
|
per_cpu(cpu_profile_hits, cpu)[1]
|
|
= (struct profile_hit *)page_address(page);
|
|
page = alloc_pages_node(node,
|
|
GFP_KERNEL | __GFP_ZERO | GFP_THISNODE,
|
|
0);
|
|
if (!page)
|
|
goto out_cleanup;
|
|
per_cpu(cpu_profile_hits, cpu)[0]
|
|
= (struct profile_hit *)page_address(page);
|
|
}
|
|
return 0;
|
|
out_cleanup:
|
|
prof_on = 0;
|
|
smp_mb();
|
|
on_each_cpu(profile_nop, NULL, 0, 1);
|
|
for_each_online_cpu(cpu) {
|
|
struct page *page;
|
|
|
|
if (per_cpu(cpu_profile_hits, cpu)[0]) {
|
|
page = virt_to_page(per_cpu(cpu_profile_hits, cpu)[0]);
|
|
per_cpu(cpu_profile_hits, cpu)[0] = NULL;
|
|
__free_page(page);
|
|
}
|
|
if (per_cpu(cpu_profile_hits, cpu)[1]) {
|
|
page = virt_to_page(per_cpu(cpu_profile_hits, cpu)[1]);
|
|
per_cpu(cpu_profile_hits, cpu)[1] = NULL;
|
|
__free_page(page);
|
|
}
|
|
}
|
|
return -1;
|
|
}
|
|
#else
|
|
#define create_hash_tables() ({ 0; })
|
|
#endif
|
|
|
|
static int __init create_proc_profile(void)
|
|
{
|
|
struct proc_dir_entry *entry;
|
|
|
|
if (!prof_on)
|
|
return 0;
|
|
if (create_hash_tables())
|
|
return -1;
|
|
if (!(entry = create_proc_entry("profile", S_IWUSR | S_IRUGO, NULL)))
|
|
return 0;
|
|
entry->proc_fops = &proc_profile_operations;
|
|
entry->size = (1+prof_len) * sizeof(atomic_t);
|
|
hotcpu_notifier(profile_cpu_callback, 0);
|
|
return 0;
|
|
}
|
|
module_init(create_proc_profile);
|
|
#endif /* CONFIG_PROC_FS */
|