diff options
| -rw-r--r-- | include/linux/writeback.h | 2 | ||||
| -rw-r--r-- | kernel/exit.c | 3 | ||||
| -rw-r--r-- | mm/page-writeback.c | 27 |
3 files changed, 32 insertions, 0 deletions
diff --git a/include/linux/writeback.h b/include/linux/writeback.h index a378c29..05eaf5e 100644 --- a/include/linux/writeback.h +++ b/include/linux/writeback.h @@ -7,6 +7,8 @@ #include <linux/sched.h> #include <linux/fs.h> +DECLARE_PER_CPU(int, dirty_throttle_leaks); + /* * The 1/4 region under the global dirty thresh is for smooth dirty throttling: * diff --git a/kernel/exit.c b/kernel/exit.c index d0b7d98..d4aac24 100644 --- a/kernel/exit.c +++ b/kernel/exit.c @@ -51,6 +51,7 @@ #include <trace/events/sched.h> #include <linux/hw_breakpoint.h> #include <linux/oom.h> +#include <linux/writeback.h> #include <asm/uaccess.h> #include <asm/unistd.h> @@ -1037,6 +1038,8 @@ NORET_TYPE void do_exit(long code) validate_creds_for_do_exit(tsk); preempt_disable(); + if (tsk->nr_dirtied) + __this_cpu_add(dirty_throttle_leaks, tsk->nr_dirtied); exit_rcu(); /* causes final put_task_struct in finish_task_switch(). */ tsk->state = TASK_DEAD; diff --git a/mm/page-writeback.c b/mm/page-writeback.c index 50f0824..619c445 100644 --- a/mm/page-writeback.c +++ b/mm/page-writeback.c @@ -1214,6 +1214,22 @@ void set_page_dirty_balance(struct page *page, int page_mkwrite) static DEFINE_PER_CPU(int, bdp_ratelimits); +/* + * Normal tasks are throttled by + * loop { + * dirty tsk->nr_dirtied_pause pages; + * take a snap in balance_dirty_pages(); + * } + * However there is a worst case. If every task exit immediately when dirtied + * (tsk->nr_dirtied_pause - 1) pages, balance_dirty_pages() will never be + * called to throttle the page dirties. The solution is to save the not yet + * throttled page dirties in dirty_throttle_leaks on task exit and charge them + * randomly into the running tasks. This works well for the above worst case, + * as the new task will pick up and accumulate the old task's leaked dirty + * count and eventually get throttled. + */ +DEFINE_PER_CPU(int, dirty_throttle_leaks) = 0; + /** * balance_dirty_pages_ratelimited_nr - balance dirty memory state * @mapping: address_space which was dirtied @@ -1261,6 +1277,17 @@ void balance_dirty_pages_ratelimited_nr(struct address_space *mapping, 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_throttle_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)) |
