2011-8-1 21:13:48-优快云博客

本文介绍了Linux内核中的Per-CPU数据管理机制，包括如何为每个CPU分配和释放内存空间，以及如何使用掩码指定多个CPU进行操作。此外，还详细描述了阻塞队列的管理和操作，如设置阻塞状态、清除阻塞状态并唤醒等待进程等。

2011-8-1 21:13:48

struct percpu_data {
void *ptrs[NR_CPUS];
};

#define __percpu_disguise(pdata) (struct percpu_data *)~(unsigned long)(pdata)

每cpu数据

void percpu_depopulate(void *__pdata, int cpu)
{
struct percpu_data *pdata = __percpu_disguise(__pdata);

kfree(pdata->ptrs[cpu]);
pdata->ptrs[cpu] = NULL;
}

释放指定CPU的perCpu数据

void __percpu_depopulate_mask(void *__pdata, cpumask_t *mask)
{
int cpu;
for_each_cpu_mask(cpu, *mask)
percpu_depopulate(__pdata, cpu);
}

用掩码的形式指定一些CPU来释放数据

void *percpu_populate(void *__pdata, size_t size, gfp_t gfp, int cpu)
{
struct percpu_data *pdata = __percpu_disguise(__pdata);
int node = cpu_to_node(cpu);

BUG_ON(pdata->ptrs[cpu]);
if (node_online(node)) {
  /* FIXME: kzalloc_node(size, gfp, node) */
  pdata->ptrs[cpu] = kmalloc_node(size, gfp, node);
  if (pdata->ptrs[cpu])
   memset(pdata->ptrs[cpu], 0, size);
} else
  pdata->ptrs[cpu] = kzalloc(size, gfp);
return pdata->ptrs[cpu];
}

如果CPU有节点就在节点上分配

static wait_queue_head_t congestion_wqh[2] = {
__WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[0]),
__WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[1])
};

有2个阻塞队列

void clear_bdi_congested(struct backing_dev_info *bdi, int rw)
{
enum bdi_state bit;
wait_queue_head_t *wqh = &congestion_wqh[rw];

bit = (rw == WRITE) ? BDI_write_congested : BDI_read_congested;
clear_bit(bit, &bdi->state);
smp_mb__after_clear_bit();
if (waitqueue_active(wqh))
wake_up(wqh);
}

清除阻塞队列唤醒阻塞进程

void set_bdi_congested(struct backing_dev_info *bdi, int rw)
{
enum bdi_state bit;

bit = (rw == WRITE) ? BDI_write_congested : BDI_read_congested;
set_bit(bit, &bdi->state);
}

设置阻塞

long congestion_wait(int rw, long timeout)
{
long ret;
DEFINE_WAIT(wait);
wait_queue_head_t *wqh = &congestion_wqh[rw];

prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE);
ret = io_schedule_timeout(timeout);
finish_wait(wqh, &wait);
return ret;
}

把自己加入到等待队列中，并设置阻塞超时

long congestion_wait_interruptible(int rw, long timeout)
{
long ret;
DEFINE_WAIT(wait);
wait_queue_head_t *wqh = &congestion_wqh[rw];

prepare_to_wait(wqh, &wait, TASK_INTERRUPTIBLE);
if (signal_pending(current))
ret = -ERESTARTSYS;
else
ret = io_schedule_timeout(timeout);
finish_wait(wqh, &wait);
return ret;
}

可信号唤醒的阻塞等待

void congestion_end(int rw)
{
wait_queue_head_t *wqh = &congestion_wqh[rw];

if (waitqueue_active(wqh))
wake_up(wqh);
}

阻塞结束