The solution is to charge the pages dirtied by the exited gcc to the
other random gcc/dd instances. It sounds not perfect, however should
behave good enough in practice.

CC: Peter Zijlstra <redacted>
Signed-off-by: Wu Fengguang <redacted>
---
 include/linux/writeback.h |    2 ++
 kernel/exit.c             |    2 ++
 mm/page-writeback.c       |   12 ++++++++++++
 3 files changed, 16 insertions(+)

--- linux-next.orig/include/linux/writeback.h	2011-08-29 19:14:22.000000000 +0800
+++ linux-next/include/linux/writeback.h	2011-08-29 19:14:32.000000000 +0800

@@ -7,6 +7,8 @@
 #include <linux/sched.h>
 #include <linux/fs.h>
 
+DECLARE_PER_CPU(int, dirty_leaks);
+
 /*
  * The 1/4 region under the global dirty thresh is for smooth dirty throttling:
  *
--- linux-next.orig/mm/page-writeback.c	2011-08-29 19:14:22.000000000 +0800
+++ linux-next/mm/page-writeback.c	2011-08-29 19:14:32.000000000 +0800

@@ -1237,6 +1237,7 @@ void set_page_dirty_balance(struct page 
 }
 
 static DEFINE_PER_CPU(int, bdp_ratelimits);
+DEFINE_PER_CPU(int, dirty_leaks) = 0;
 
 /**
  * balance_dirty_pages_ratelimited_nr - balance dirty memory state

@@ -1285,6 +1286,17 @@ void balance_dirty_pages_ratelimited_nr(
 			ratelimit = 0;
 		}
 	}
+	/*
+	 * Pick up the dirtied pages by the exited tasks. This avoids lots of
+	 * short-lived tasks (eg. gcc invocations in a kernel build) escaping
+	 * the dirty throttling and livelock other long-run dirtiers.
+	 */
+	p = &__get_cpu_var(dirty_leaks);
+	if (*p > 0 && current->nr_dirtied < ratelimit) {
+		nr_pages_dirtied = min(*p, ratelimit - current->nr_dirtied);
+		*p -= nr_pages_dirtied;
+		current->nr_dirtied += nr_pages_dirtied;
+	}
 	preempt_enable();
 
 	if (unlikely(current->nr_dirtied >= ratelimit))
--- linux-next.orig/kernel/exit.c	2011-08-26 16:19:27.000000000 +0800
+++ linux-next/kernel/exit.c	2011-08-29 19:14:22.000000000 +0800

@@ -1044,6 +1044,8 @@ NORET_TYPE void do_exit(long code)
 	validate_creds_for_do_exit(tsk);
 
 	preempt_disable();
+	if (tsk->nr_dirtied)
+		__this_cpu_add(dirty_leaks, tsk->nr_dirtied);
 	exit_rcu();
 	/* causes final put_task_struct in finish_task_switch(). */
 	tsk->state = TASK_DEAD;