[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, 10 insertions, 3 deletions

diff --git a/include/linux/sched.h b/include/linux/sched.h
index eafe4a7b8237..cad6a16260f7 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -344,9 +344,16 @@ struct mm_struct {
         /* Architecture-specific MM context */
         mm_context_t context;
 
-        /* Token based thrashing protection. */
-        unsigned long swap_token_time;
-        char recent_pagein;
+        /* Swap token stuff */
+        /*
+         * Last value of global fault stamp as seen by this process.
+         * In other words, this value gives an indication of how long
+         * it has been since this task got the token.
+         * Look at mm/thrash.c
+         */
+        unsigned int faultstamp;
+        unsigned int token_priority;
+        unsigned int last_interval;
 
         /* coredumping support */
         int core_waiters;