Revision ea164d73a7a0b2b2be3a1d8c2a8a4dab8999fa9c authored by Andrea Arcangeli on 28 November 2005, 21:44:15 UTC, committed by Linus Torvalds on 28 November 2005, 22:42:26 UTC
With Andrew Morton <akpm@osdl.org> The slab scanning code tries to balance the scanning rate of slabs versus the scanning rate of LRU pages. To do this, it retains state concerning how many slabs have been scanned - if a particular slab shrinker didn't scan enough objects, we remember that for next time, and scan more objects on the next pass. The problem with this is that with (say) a huge number of GFP_NOIO direct-reclaim attempts, the number of objects which are to be scanned when we finally get a GFP_KERNEL request can be huge. Because some shrinker handlers just bail out if !__GFP_FS. So the patch clamps the number of objects-to-be-scanned to 2* the total number of objects in the slab cache. Signed-off-by: Andrea Arcangeli <andrea@suse.de> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
1 parent 154f484
stop_machine.c
#include <linux/stop_machine.h>
#include <linux/kthread.h>
#include <linux/sched.h>
#include <linux/cpu.h>
#include <linux/err.h>
#include <linux/syscalls.h>
#include <asm/atomic.h>
#include <asm/semaphore.h>
#include <asm/uaccess.h>
/* Since we effect priority and affinity (both of which are visible
* to, and settable by outside processes) we do indirection via a
* kthread. */
/* Thread to stop each CPU in user context. */
enum stopmachine_state {
STOPMACHINE_WAIT,
STOPMACHINE_PREPARE,
STOPMACHINE_DISABLE_IRQ,
STOPMACHINE_EXIT,
};
static enum stopmachine_state stopmachine_state;
static unsigned int stopmachine_num_threads;
static atomic_t stopmachine_thread_ack;
static DECLARE_MUTEX(stopmachine_mutex);
static int stopmachine(void *cpu)
{
int irqs_disabled = 0;
int prepared = 0;
set_cpus_allowed(current, cpumask_of_cpu((int)(long)cpu));
/* Ack: we are alive */
smp_mb(); /* Theoretically the ack = 0 might not be on this CPU yet. */
atomic_inc(&stopmachine_thread_ack);
/* Simple state machine */
while (stopmachine_state != STOPMACHINE_EXIT) {
if (stopmachine_state == STOPMACHINE_DISABLE_IRQ
&& !irqs_disabled) {
local_irq_disable();
irqs_disabled = 1;
/* Ack: irqs disabled. */
smp_mb(); /* Must read state first. */
atomic_inc(&stopmachine_thread_ack);
} else if (stopmachine_state == STOPMACHINE_PREPARE
&& !prepared) {
/* Everyone is in place, hold CPU. */
preempt_disable();
prepared = 1;
smp_mb(); /* Must read state first. */
atomic_inc(&stopmachine_thread_ack);
}
/* Yield in first stage: migration threads need to
* help our sisters onto their CPUs. */
if (!prepared && !irqs_disabled)
yield();
else
cpu_relax();
}
/* Ack: we are exiting. */
smp_mb(); /* Must read state first. */
atomic_inc(&stopmachine_thread_ack);
if (irqs_disabled)
local_irq_enable();
if (prepared)
preempt_enable();
return 0;
}
/* Change the thread state */
static void stopmachine_set_state(enum stopmachine_state state)
{
atomic_set(&stopmachine_thread_ack, 0);
smp_wmb();
stopmachine_state = state;
while (atomic_read(&stopmachine_thread_ack) != stopmachine_num_threads)
cpu_relax();
}
static int stop_machine(void)
{
int i, ret = 0;
struct sched_param param = { .sched_priority = MAX_RT_PRIO-1 };
mm_segment_t old_fs = get_fs();
/* One high-prio thread per cpu. We'll do this one. */
set_fs(KERNEL_DS);
sys_sched_setscheduler(current->pid, SCHED_FIFO,
(struct sched_param __user *)¶m);
set_fs(old_fs);
atomic_set(&stopmachine_thread_ack, 0);
stopmachine_num_threads = 0;
stopmachine_state = STOPMACHINE_WAIT;
for_each_online_cpu(i) {
if (i == raw_smp_processor_id())
continue;
ret = kernel_thread(stopmachine, (void *)(long)i,CLONE_KERNEL);
if (ret < 0)
break;
stopmachine_num_threads++;
}
/* Wait for them all to come to life. */
while (atomic_read(&stopmachine_thread_ack) != stopmachine_num_threads)
yield();
/* If some failed, kill them all. */
if (ret < 0) {
stopmachine_set_state(STOPMACHINE_EXIT);
up(&stopmachine_mutex);
return ret;
}
/* Now they are all started, make them hold the CPUs, ready. */
preempt_disable();
stopmachine_set_state(STOPMACHINE_PREPARE);
/* Make them disable irqs. */
local_irq_disable();
stopmachine_set_state(STOPMACHINE_DISABLE_IRQ);
return 0;
}
static void restart_machine(void)
{
stopmachine_set_state(STOPMACHINE_EXIT);
local_irq_enable();
preempt_enable_no_resched();
}
struct stop_machine_data
{
int (*fn)(void *);
void *data;
struct completion done;
};
static int do_stop(void *_smdata)
{
struct stop_machine_data *smdata = _smdata;
int ret;
ret = stop_machine();
if (ret == 0) {
ret = smdata->fn(smdata->data);
restart_machine();
}
/* We're done: you can kthread_stop us now */
complete(&smdata->done);
/* Wait for kthread_stop */
set_current_state(TASK_INTERRUPTIBLE);
while (!kthread_should_stop()) {
schedule();
set_current_state(TASK_INTERRUPTIBLE);
}
__set_current_state(TASK_RUNNING);
return ret;
}
struct task_struct *__stop_machine_run(int (*fn)(void *), void *data,
unsigned int cpu)
{
struct stop_machine_data smdata;
struct task_struct *p;
smdata.fn = fn;
smdata.data = data;
init_completion(&smdata.done);
down(&stopmachine_mutex);
/* If they don't care which CPU fn runs on, bind to any online one. */
if (cpu == NR_CPUS)
cpu = raw_smp_processor_id();
p = kthread_create(do_stop, &smdata, "kstopmachine");
if (!IS_ERR(p)) {
kthread_bind(p, cpu);
wake_up_process(p);
wait_for_completion(&smdata.done);
}
up(&stopmachine_mutex);
return p;
}
int stop_machine_run(int (*fn)(void *), void *data, unsigned int cpu)
{
struct task_struct *p;
int ret;
/* No CPUs can come up or down during this. */
lock_cpu_hotplug();
p = __stop_machine_run(fn, data, cpu);
if (!IS_ERR(p))
ret = kthread_stop(p);
else
ret = PTR_ERR(p);
unlock_cpu_hotplug();
return ret;
}
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