#include <linux/sysctl.h>
#include <linux/cpu.h>
#include <linux/syscalls.h>
-#include <linux/buffer_head.h>
+#include <linux/buffer_head.h> /* __set_page_dirty_buffers */
#include <linux/pagevec.h>
#include <trace/events/writeback.h>
*/
static struct prop_descriptor vm_completions;
+/*
+ * Work out the current dirty-memory clamping and background writeout
+ * thresholds.
+ *
+ * The main aim here is to lower them aggressively if there is a lot of mapped
+ * memory around. To avoid stressing page reclaim with lots of unreclaimable
+ * pages. It is better to clamp down on writers than to start swapping, and
+ * performing lots of scanning.
+ *
+ * We only allow 1/2 of the currently-unmapped memory to be dirtied.
+ *
+ * We don't permit the clamping level to fall below 5% - that is getting rather
+ * excessive.
+ *
+ * We make sure that the background writeout level is below the adjusted
+ * clamping level.
+ */
+
+/*
+ * In a memory zone, there is a certain amount of pages we consider
+ * available for the page cache, which is essentially the number of
+ * free and reclaimable pages, minus some zone reserves to protect
+ * lowmem and the ability to uphold the zone's watermarks without
+ * requiring writeback.
+ *
+ * This number of dirtyable pages is the base value of which the
+ * user-configurable dirty ratio is the effictive number of pages that
+ * are allowed to be actually dirtied. Per individual zone, or
+ * globally by using the sum of dirtyable pages over all zones.
+ *
+ * Because the user is allowed to specify the dirty limit globally as
+ * absolute number of bytes, calculating the per-zone dirty limit can
+ * require translating the configured limit into a percentage of
+ * global dirtyable memory first.
+ */
+
+static unsigned long highmem_dirtyable_memory(unsigned long total)
+{
+#ifdef CONFIG_HIGHMEM
+ int node;
+ unsigned long x = 0;
+
+ for_each_node_state(node, N_HIGH_MEMORY) {
+ struct zone *z =
+ &NODE_DATA(node)->node_zones[ZONE_HIGHMEM];
+
+ x += zone_page_state(z, NR_FREE_PAGES) +
+ zone_reclaimable_pages(z) - z->dirty_balance_reserve;
+ }
+ /*
+ * Make sure that the number of highmem pages is never larger
+ * than the number of the total dirtyable memory. This can only
+ * occur in very strange VM situations but we want to make sure
+ * that this does not occur.
+ */
+ return min(x, total);
+#else
+ return 0;
+#endif
+}
+
+/**
+ * global_dirtyable_memory - number of globally dirtyable pages
+ *
+ * Returns the global number of pages potentially available for dirty
+ * page cache. This is the base value for the global dirty limits.
+ */
+unsigned long global_dirtyable_memory(void)
+{
+ unsigned long x;
+
+ x = global_page_state(NR_FREE_PAGES) + global_reclaimable_pages() -
+ dirty_balance_reserve;
+
+ if (!vm_highmem_is_dirtyable)
+ x -= highmem_dirtyable_memory(x);
+
+ 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);
+}
+
+/**
+ * zone_dirtyable_memory - number of dirtyable pages in a zone
+ * @zone: the zone
+ *
+ * Returns the zone's number of pages potentially available for dirty
+ * page cache. This is the base value for the per-zone dirty limits.
+ */
+static unsigned long zone_dirtyable_memory(struct zone *zone)
+{
+ /*
+ * The effective global number of dirtyable pages may exclude
+ * highmem as a big-picture measure to keep the ratio between
+ * dirty memory and lowmem reasonable.
+ *
+ * But this function is purely about the individual zone and a
+ * highmem zone can hold its share of dirty pages, so we don't
+ * care about vm_highmem_is_dirtyable here.
+ */
+ return zone_page_state(zone, NR_FREE_PAGES) +
+ zone_reclaimable_pages(zone) -
+ zone->dirty_balance_reserve;
+}
+
+/**
+ * zone_dirty_limit - maximum number of dirty pages allowed in a zone
+ * @zone: the zone
+ *
+ * Returns the maximum number of dirty pages allowed in a zone, based
+ * on the zone's dirtyable memory.
+ */
+static unsigned long zone_dirty_limit(struct zone *zone)
+{
+ unsigned long zone_memory = zone_dirtyable_memory(zone);
+ struct task_struct *tsk = current;
+ unsigned long dirty;
+
+ if (vm_dirty_bytes)
+ dirty = DIV_ROUND_UP(vm_dirty_bytes, PAGE_SIZE) *
+ zone_memory / global_dirtyable_memory();
+ else
+ dirty = vm_dirty_ratio * zone_memory / 100;
+
+ if (tsk->flags & PF_LESS_THROTTLE || rt_task(tsk))
+ dirty += dirty / 4;
+
+ return dirty;
+}
+
+/**
+ * zone_dirty_ok - tells whether a zone is within its dirty limits
+ * @zone: the zone to check
+ *
+ * Returns %true when the dirty pages in @zone are within the zone's
+ * dirty limit, %false if the limit is exceeded.
+ */
+bool zone_dirty_ok(struct zone *zone)
+{
+ unsigned long limit = zone_dirty_limit(zone);
+
+ return zone_page_state(zone, NR_FILE_DIRTY) +
+ zone_page_state(zone, NR_UNSTABLE_NFS) +
+ zone_page_state(zone, NR_WRITEBACK) <= limit;
+}
+
/*
* couple the period to the dirty_ratio:
*
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);
}
return ret;
}
-
int dirty_bytes_handler(struct ctl_table *table, int write,
void __user *buffer, size_t *lenp,
loff_t *ppos)
}
EXPORT_SYMBOL(bdi_set_max_ratio);
-/*
- * Work out the current dirty-memory clamping and background writeout
- * thresholds.
- *
- * The main aim here is to lower them aggressively if there is a lot of mapped
- * memory around. To avoid stressing page reclaim with lots of unreclaimable
- * pages. It is better to clamp down on writers than to start swapping, and
- * performing lots of scanning.
- *
- * We only allow 1/2 of the currently-unmapped memory to be dirtied.
- *
- * We don't permit the clamping level to fall below 5% - that is getting rather
- * excessive.
- *
- * 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
- int node;
- unsigned long x = 0;
-
- for_each_node_state(node, N_HIGH_MEMORY) {
- struct zone *z =
- &NODE_DATA(node)->node_zones[ZONE_HIGHMEM];
-
- x += zone_page_state(z, NR_FREE_PAGES) +
- zone_reclaimable_pages(z);
- }
- /*
- * Make sure that the number of highmem pages is never larger
- * than the number of the total dirtyable memory. This can only
- * occur in very strange VM situations but we want to make sure
- * that this does not occur.
- */
- return min(x, total);
-#else
- return 0;
-#endif
-}
-
-/**
- * determine_dirtyable_memory - amount of memory that may be used
- *
- * Returns the numebr of pages that can currently be freed and used
- * by the kernel for direct mappings.
- */
-unsigned long determine_dirtyable_memory(void)
-{
- unsigned long x;
-
- x = global_page_state(NR_FREE_PAGES) + global_reclaimable_pages();
-
- if (!vm_highmem_is_dirtyable)
- x -= highmem_dirtyable_memory(x);
-
- return x + 1; /* Ensure that we never return 0 */
-}
-
static unsigned long dirty_freerun_ceiling(unsigned long thresh,
unsigned long bg_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
projects / cascardo / linux.git / blobdiff