Exemple #1
0
void
get_dirty_limits(unsigned long *pbackground, unsigned long *pdirty,
		 unsigned long *pbdi_dirty, struct backing_dev_info *bdi)
{
	unsigned long background;
	unsigned long dirty;
	unsigned long uninitialized_var(available_memory);
	struct task_struct *tsk;

	if (!vm_dirty_bytes || !dirty_background_bytes)
    		available_memory = determine_dirtyable_memory();

	if (vm_dirty_bytes)
		dirty = DIV_ROUND_UP(vm_dirty_bytes, PAGE_SIZE);
	else {
		int dirty_ratio;

		dirty_ratio = vm_dirty_ratio;
		if (dirty_ratio < 5)
			dirty_ratio = 5;
		dirty = (dirty_ratio * available_memory) / 100;
	}

	if (dirty_background_bytes)
		background = DIV_ROUND_UP(dirty_background_bytes, PAGE_SIZE);
	else
		background = (dirty_background_ratio * available_memory) / 100;

	if (background >= dirty)
		background = dirty / 2;
	tsk = current;
	if (tsk->flags & PF_LESS_THROTTLE || rt_task(tsk)) {
		background += background / 4;
		dirty += dirty / 4;
	}
	*pbackground = background;
	*pdirty = dirty;

	if (bdi) {
		u64 bdi_dirty;
		long numerator, denominator;

		/*
		 * Calculate this BDI's share of the dirty ratio.
		 */
		bdi_writeout_fraction(bdi, &numerator, &denominator);

		bdi_dirty = (dirty * (100 - bdi_min_ratio)) / 100;
		bdi_dirty *= numerator;
		do_div(bdi_dirty, denominator);
		bdi_dirty += (dirty * bdi->min_ratio) / 100;
		if (bdi_dirty > (dirty * bdi->max_ratio) / 100)
			bdi_dirty = dirty * bdi->max_ratio / 100;

		*pbdi_dirty = bdi_dirty;
		clip_bdi_dirty_limit(bdi, dirty, pbdi_dirty);
		task_dirty_limit(current, pbdi_dirty);
	}
}
void
get_dirty_limits(long *pbackground, long *pdirty, long *pbdi_dirty,
		 struct backing_dev_info *bdi)
{
	int background_ratio;		/* Percentages */
	int dirty_ratio;
	long background;
	long dirty;
	unsigned long available_memory = determine_dirtyable_memory();
	struct task_struct *tsk;

	dirty_ratio = vm_dirty_ratio;
	if (dirty_ratio < 5)
		dirty_ratio = 5;

	background_ratio = dirty_background_ratio;
	if (background_ratio >= dirty_ratio)
		background_ratio = dirty_ratio / 2;

	background = (background_ratio * available_memory) / 100;
	dirty = (dirty_ratio * available_memory) / 100;
	tsk = current;
	if (tsk->flags & PF_LESS_THROTTLE || rt_task(tsk)) {
		background += background / 4;
		dirty += dirty / 4;
	}
	*pbackground = background;
	*pdirty = dirty;

	if (bdi) {
		u64 bdi_dirty;
		long numerator, denominator;

		/*
		 * Calculate this BDI's share of the dirty ratio.
		 */
		bdi_writeout_fraction(bdi, &numerator, &denominator);

		bdi_dirty = (dirty * (100 - bdi_min_ratio)) / 100;
		bdi_dirty *= numerator;
		do_div(bdi_dirty, denominator);
		bdi_dirty += (dirty * bdi->min_ratio) / 100;
		if (bdi_dirty > (dirty * bdi->max_ratio) / 100)
			bdi_dirty = dirty * bdi->max_ratio / 100;

		*pbdi_dirty = bdi_dirty;
		clip_bdi_dirty_limit(bdi, dirty, pbdi_dirty);
		task_dirty_limit(current, pbdi_dirty);
	}
}
/**
 * bdi_dirty_limit - @bdi's share of dirty throttling threshold
 * @bdi: the backing_dev_info to query
 * @dirty: global dirty limit in pages
 * @dirty_pages: current number of dirty pages
 *
 * Returns @bdi's dirty limit in pages. The term "dirty" in the context of
 * dirty balancing includes all PG_dirty, PG_writeback and NFS unstable pages.
 *
 * It allocates high/low dirty limits to fast/slow devices, in order to prevent
 * - starving fast devices
 * - piling up dirty pages (that will take long time to sync) on slow devices
 *
 * The bdi's share of dirty limit will be adapting to its throughput and
 * bounded by the bdi->min_ratio and/or bdi->max_ratio parameters, if set.
 *
 * There is a chicken and egg problem: when bdi A (eg. /pub) is heavy dirtied
 * and bdi B (eg. /) is light dirtied hence has 0 dirty limit, tasks writing to
 * B always get heavily throttled and bdi B's dirty limit might never be able
 * to grow up from 0. So we do tricks to reserve some global margin and honour
 * it to the bdi's that run low.
 */
unsigned long bdi_dirty_limit(struct backing_dev_info *bdi,
			      unsigned long dirty,
			      unsigned long dirty_pages)
{
	u64 bdi_dirty;
	long numerator, denominator;

	/*
	 * try to prevent "global limit exceeded but bdi limit not exceeded"
	 */
	if (likely(dirty > bdi_stat_error(bdi)))
		dirty -= bdi_stat_error(bdi);
	else
		return 0;

	/*
	 * Provide a global safety margin of ~1%, or up to 32MB for a 20GB box.
	 */
	dirty -= min(dirty / 128, 32768UL >> (PAGE_SHIFT-10));

	/*
	 * Calculate this BDI's share of the dirty ratio.
	 */
	bdi_writeout_fraction(bdi, &numerator, &denominator);

	bdi_dirty = (dirty * (100 - bdi_min_ratio)) / 100;
	bdi_dirty *= numerator;
	do_div(bdi_dirty, denominator);

	bdi_dirty += (dirty * bdi->min_ratio) / 100;

	/*
	 * If we can dirty N more pages globally, honour N/2 to the bdi that
	 * runs low, so as to help it ramp up.
	 */
	if (unlikely(bdi_dirty < (dirty - dirty_pages) / 2 &&
		     dirty > dirty_pages))
		bdi_dirty = (dirty - dirty_pages) / 2;

	if (bdi_dirty > (dirty * bdi->max_ratio) / 100)
		bdi_dirty = dirty * bdi->max_ratio / 100;

	return bdi_dirty;
}
/*
 * bdi_dirty_limit - @bdi's share of dirty throttling threshold
 *
 * Allocate high/low dirty limits to fast/slow devices, in order to prevent
 * - starving fast devices
 * - piling up dirty pages (that will take long time to sync) on slow devices
 *
 * The bdi's share of dirty limit will be adapting to its throughput and
 * bounded by the bdi->min_ratio and/or bdi->max_ratio parameters, if set.
 */
unsigned long bdi_dirty_limit(struct backing_dev_info *bdi, unsigned long dirty)
{
	u64 bdi_dirty;
	long numerator, denominator;

	/*
	 * Calculate this BDI's share of the dirty ratio.
	 */
	bdi_writeout_fraction(bdi, &numerator, &denominator);

	bdi_dirty = (dirty * (100 - bdi_min_ratio)) / 100;
	bdi_dirty *= numerator;
	do_div(bdi_dirty, denominator);

	bdi_dirty += (dirty * bdi->min_ratio) / 100;
	if (bdi_dirty > (dirty * bdi->max_ratio) / 100)
		bdi_dirty = dirty * bdi->max_ratio / 100;

	return bdi_dirty;
}