Commit ccafa287 authored by Johannes Weiner's avatar Johannes Weiner Committed by Linus Torvalds
Browse files

mm: writeback: cleanups in preparation for per-zone dirty limits 



The next patch will introduce per-zone dirty limiting functions in
addition to the traditional global dirty limiting.

Rename determine_dirtyable_memory() to global_dirtyable_memory() before
adding the zone-specific version, and fix up its documentation.

Also, move the functions to determine the dirtyable memory and the
function to calculate the dirty limit based on that together so that their
relationship is more apparent and that they can be commented on as a
group.

Signed-off-by: default avatarJohannes Weiner <jweiner@redhat.com>
Reviewed-by: default avatarMinchan Kim <minchan.kim@gmail.com>
Acked-by: default avatarMel Gorman <mel@suse.de>
Reviewed-by: default avatarMichal Hocko <mhocko@suse.cz>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Wu Fengguang <fengguang.wu@intel.com>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Shaohua Li <shaohua.li@intel.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Chris Mason <chris.mason@oracle.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent ab8fabd4

mm/page-writeback.c

+47 −46
Original line number Diff line number Diff line
@@ -146,6 +146,7 @@ static struct prop_descriptor vm_completions; 
 * We make sure that the background writeout level is below the adjusted

 * clamping level.

 */



static unsigned long highmem_dirtyable_memory(unsigned long total)

{

#ifdef CONFIG_HIGHMEM
@@ -172,12 +173,12 @@ static unsigned long highmem_dirtyable_memory(unsigned long total) 
}



/**

 * determine_dirtyable_memory - amount of memory that may be used

 * global_dirtyable_memory - number of globally dirtyable pages

 *

 * Returns the numebr of pages that can currently be freed and used

 * by the kernel for direct mappings.

 * Returns the global number of pages potentially available for dirty

 * page cache.  This is the base value for the global dirty limits.

 */

static unsigned long determine_dirtyable_memory(void)

unsigned long global_dirtyable_memory(void)

{

	unsigned long x;
@@ -190,6 +191,47 @@ static unsigned long determine_dirtyable_memory(void) 
	return x + 1;	/* Ensure that we never return 0 */

}



/*

 * global_dirty_limits - background-writeback and dirty-throttling thresholds

 *

 * Calculate the dirty thresholds based on sysctl parameters

 * - vm.dirty_background_ratio  or  vm.dirty_background_bytes

 * - vm.dirty_ratio             or  vm.dirty_bytes

 * The dirty limits will be lifted by 1/4 for PF_LESS_THROTTLE (ie. nfsd) and

 * real-time tasks.

 */

void global_dirty_limits(unsigned long *pbackground, unsigned long *pdirty)

{

	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 = global_dirtyable_memory();



	if (vm_dirty_bytes)

		dirty = DIV_ROUND_UP(vm_dirty_bytes, PAGE_SIZE);

	else

		dirty = (vm_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;

	trace_global_dirty_state(background, dirty);

}



/*

 * couple the period to the dirty_ratio:

 *
@@ -202,7 +244,7 @@ static int calc_period_shift(void) 
	if (vm_dirty_bytes)

		dirty_total = vm_dirty_bytes / PAGE_SIZE;

	else

		dirty_total = (vm_dirty_ratio * determine_dirtyable_memory()) /

		dirty_total = (vm_dirty_ratio * global_dirtyable_memory()) /

				100;

	return 2 + ilog2(dirty_total - 1);

}
@@ -362,47 +404,6 @@ static unsigned long hard_dirty_limit(unsigned long thresh) 
	return max(thresh, global_dirty_limit);

}



/*

 * global_dirty_limits - background-writeback and dirty-throttling thresholds

 *

 * Calculate the dirty thresholds based on sysctl parameters

 * - vm.dirty_background_ratio  or  vm.dirty_background_bytes

 * - vm.dirty_ratio             or  vm.dirty_bytes

 * The dirty limits will be lifted by 1/4 for PF_LESS_THROTTLE (ie. nfsd) and

 * real-time tasks.

 */

void global_dirty_limits(unsigned long *pbackground, unsigned long *pdirty)

{

	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

		dirty = (vm_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;

	trace_global_dirty_state(background, dirty);

}



/**

 * bdi_dirty_limit - @bdi's share of dirty throttling threshold

 * @bdi: the backing_dev_info to query

CRA Git | Maintained and supported by SUSTech CRA and CCSE