Based on ideas of Andrew:
http://marc.info/?l=linux-kernel&m=102912915020543&w=2
Scale the bdi dirty limit inversly with the tasks dirty rate.
This makes heavy writers have a lower dirty limit than the occasional writer.
Andrea proposed something similar:
http://lwn.net/Articles/152277/
The main disadvantage to his patch is that he uses an unrelated quantity to
measure time, which leaves him with a workload dependant tunable. Other than
that the two approaches appear quite similar.
Signed-off-by: Peter Zijlstra <[email protected]>
---
Changes since -v8:
- initialized init_task
- moved the prop_local init after the task_struct copy
- changed the per task ratio to 1/8 (from 1/2).
- explicit usage of prop_local_single
include/linux/init_task.h | 1
include/linux/sched.h | 2 +
kernel/fork.c | 10 +++++++++
mm/page-writeback.c | 50 +++++++++++++++++++++++++++++++++++++++++++++-
4 files changed, 62 insertions(+), 1 deletion(-)
Index: linux-2.6/include/linux/sched.h
===================================================================
--- linux-2.6.orig/include/linux/sched.h
+++ linux-2.6/include/linux/sched.h
@@ -84,6 +84,7 @@ struct sched_param {
#include <linux/timer.h>
#include <linux/hrtimer.h>
#include <linux/task_io_accounting.h>
+#include <linux/proportions.h>
#include <asm/processor.h>
@@ -1125,6 +1126,7 @@ struct task_struct {
#ifdef CONFIG_FAULT_INJECTION
int make_it_fail;
#endif
+ struct prop_local_single dirties;
};
/*
Index: linux-2.6/kernel/fork.c
===================================================================
--- linux-2.6.orig/kernel/fork.c
+++ linux-2.6/kernel/fork.c
@@ -107,6 +107,7 @@ static struct kmem_cache *mm_cachep;
void free_task(struct task_struct *tsk)
{
+ prop_local_destroy_single(&tsk->dirties);
free_thread_info(tsk->stack);
rt_mutex_debug_task_free(tsk);
free_task_struct(tsk);
@@ -163,6 +164,7 @@ static struct task_struct *dup_task_stru
{
struct task_struct *tsk;
struct thread_info *ti;
+ int err;
prepare_to_copy(orig);
@@ -178,6 +180,14 @@ static struct task_struct *dup_task_stru
*tsk = *orig;
tsk->stack = ti;
+
+ err = prop_local_init_single(&tsk->dirties);
+ if (err) {
+ free_thread_info(ti);
+ free_task_struct(tsk);
+ return NULL;
+ }
+
setup_thread_stack(tsk, orig);
#ifdef CONFIG_CC_STACKPROTECTOR
Index: linux-2.6/mm/page-writeback.c
===================================================================
--- linux-2.6.orig/mm/page-writeback.c
+++ linux-2.6/mm/page-writeback.c
@@ -118,6 +118,7 @@ static void background_writeout(unsigned
*
*/
static struct prop_descriptor vm_completions;
+static struct prop_descriptor vm_dirties;
static unsigned long determine_dirtyable_memory(void);
@@ -146,6 +147,7 @@ int dirty_ratio_handler(ctl_table *table
if (ret == 0 && write && vm_dirty_ratio != old_ratio) {
int shift = calc_period_shift();
prop_change_shift(&vm_completions, shift);
+ prop_change_shift(&vm_dirties, shift);
}
return ret;
}
@@ -159,6 +161,11 @@ static inline void __bdi_writeout_inc(st
__prop_inc_percpu(&vm_completions, &bdi->completions);
}
+static inline void task_dirty_inc(struct task_struct *tsk)
+{
+ prop_inc_single(&vm_dirties, &tsk->dirties);
+}
+
/*
* Obtain an accurate fraction of the BDI's portion.
*/
@@ -198,6 +205,37 @@ clip_bdi_dirty_limit(struct backing_dev_
*pbdi_dirty = min(*pbdi_dirty, avail_dirty);
}
+static inline void task_dirties_fraction(struct task_struct *tsk,
+ long *numerator, long *denominator)
+{
+ prop_fraction_single(&vm_dirties, &tsk->dirties,
+ numerator, denominator);
+}
+
+/*
+ * scale the dirty limit
+ *
+ * task specific dirty limit:
+ *
+ * dirty -= (dirty/8) * p_{t}
+ */
+void task_dirty_limit(struct task_struct *tsk, long *pdirty)
+{
+ long numerator, denominator;
+ long dirty = *pdirty;
+ long long inv = dirty >> 3;
+
+ task_dirties_fraction(tsk, &numerator, &denominator);
+ inv *= numerator;
+ do_div(inv, denominator);
+
+ dirty -= inv;
+ if (dirty < *pdirty/2)
+ dirty = *pdirty/2;
+
+ *pdirty = dirty;
+}
+
/*
* Work out the current dirty-memory clamping and background writeout
* thresholds.
@@ -304,6 +342,7 @@ get_dirty_limits(long *pbackground, long
*pbdi_dirty = bdi_dirty;
clip_bdi_dirty_limit(bdi, dirty, pbdi_dirty);
+ task_dirty_limit(current, pbdi_dirty);
}
}
@@ -725,6 +764,7 @@ void __init page_writeback_init(void)
shift = calc_period_shift();
prop_descriptor_init(&vm_completions, shift);
+ prop_descriptor_init(&vm_dirties, shift);
}
/**
@@ -1003,7 +1043,7 @@ EXPORT_SYMBOL(redirty_page_for_writepage
* If the mapping doesn't provide a set_page_dirty a_op, then
* just fall through and assume that it wants buffer_heads.
*/
-int fastcall set_page_dirty(struct page *page)
+static int __set_page_dirty(struct page *page)
{
struct address_space *mapping = page_mapping(page);
@@ -1021,6 +1061,14 @@ int fastcall set_page_dirty(struct page
}
return 0;
}
+
+int fastcall set_page_dirty(struct page *page)
+{
+ int ret = __set_page_dirty(page);
+ if (ret)
+ task_dirty_inc(current);
+ return ret;
+}
EXPORT_SYMBOL(set_page_dirty);
/*
Index: linux-2.6/include/linux/init_task.h
===================================================================
--- linux-2.6.orig/include/linux/init_task.h
+++ linux-2.6/include/linux/init_task.h
@@ -169,6 +169,7 @@ extern struct group_info init_groups;
[PIDTYPE_PGID] = INIT_PID_LINK(PIDTYPE_PGID), \
[PIDTYPE_SID] = INIT_PID_LINK(PIDTYPE_SID), \
}, \
+ .dirties = INIT_PROP_LOCAL_SINGLE(dirties), \
INIT_TRACE_IRQFLAGS \
INIT_LOCKDEP \
}
--
-
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