[PATCH] new scheme to preempt swap token

The new swap token patches replace the current token traversal algo.  The old
algo had a crude timeout parameter that was used to handover the token from
one task to another.  This algo, transfers the token to the tasks that are in
need of the token.  The urgency for the token is based on the number of times
a task is required to swap-in pages.  Accordingly, the priority of a task is
incremented if it has been badly affected due to swap-outs.  To ensure that
the token doesnt bounce around rapidly, the token holders are given a priority
boost.  The priority of tasks is also decremented, if their rate of swap-in's
keeps reducing.  This way, the condition to check whether to pre-empt the swap
token, is a matter of comparing two task's priority fields.

[akpm@osdl.org: cleanups]
Signed-off-by: Ashwin Chaugule <ashwin.chaugule@celunite.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 8 insertions, 0 deletions

diff --git a/kernel/fork.c b/kernel/fork.c
index 8cdd3e72ba55..5678e6c61ef2 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -479,6 +479,10 @@ static struct mm_struct *dup_mm(struct task_struct *tsk)
 
         memcpy(mm, oldmm, sizeof(*mm));
 
+        /* Initializing for Swap token stuff */
+        mm->token_priority = 0;
+        mm->last_interval = 0;
+
         if (!mm_init(mm))
                 goto fail_nomem;
 
@@ -542,6 +546,10 @@ static int copy_mm(unsigned long clone_flags, struct task_struct * tsk)
                 goto fail_nomem;
 
 good_mm:
+        /* Initializing for Swap token stuff */
+        mm->token_priority = 0;
+        mm->last_interval = 0;
+
         tsk->mm = mm;
         tsk->active_mm = mm;
         return 0;