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authorWu Fengguang <fengguang.wu@intel.com>2011-06-12 03:25:42 +0200
committerWu Fengguang <fengguang.wu@intel.com>2011-12-18 07:20:27 +0100
commit83712358ba0a1497ce59a4f84ce4dd0f803fe6fc (patch)
treed17ab27a7bff50616e3b63ad137c004d9ccfbcb0 /kernel/fork.c
parentbtrfs: fix dirtied pages accounting on sub-page writes (diff)
downloadlinux-83712358ba0a1497ce59a4f84ce4dd0f803fe6fc.tar.xz
linux-83712358ba0a1497ce59a4f84ce4dd0f803fe6fc.zip
writeback: dirty ratelimit - think time compensation
Compensate the task's think time when computing the final pause time, so that ->dirty_ratelimit can be executed accurately. think time := time spend outside of balance_dirty_pages() In the rare case that the task slept longer than the 200ms period time (result in negative pause time), the sleep time will be compensated in the following periods, too, if it's less than 1 second. Accumulated errors are carefully avoided as long as the max pause area is not hitted. Pseudo code: period = pages_dirtied / task_ratelimit; think = jiffies - dirty_paused_when; pause = period - think; 1) normal case: period > think pause = period - think dirty_paused_when = jiffies + pause nr_dirtied = 0 period time |===============================>| think time pause time |===============>|==============>| ------|----------------|---------------|------------------------ dirty_paused_when jiffies 2) no pause case: period <= think don't pause; reduce future pause time by: dirty_paused_when += period nr_dirtied = 0 period time |===============================>| think time |===================================================>| ------|--------------------------------+-------------------|---- dirty_paused_when jiffies Acked-by: Jan Kara <jack@suse.cz> Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
Diffstat (limited to 'kernel/fork.c')
-rw-r--r--kernel/fork.c1
1 files changed, 1 insertions, 0 deletions
diff --git a/kernel/fork.c b/kernel/fork.c
index da4a6a10d088..f8668cf6a32d 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1296,6 +1296,7 @@ static struct task_struct *copy_process(unsigned long clone_flags,
p->nr_dirtied = 0;
p->nr_dirtied_pause = 128 >> (PAGE_SHIFT - 10);
+ p->dirty_paused_when = 0;
/*
* Ok, make it visible to the rest of the system.