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Subject[patch] 2.2.15-pre3 kswapd fix
Hi Alan,

here's a much cleaner (and hopefully slightly higher
performance) fix of the kswapd problem. The code is
also more readable now...

About Andrea's freepages.low vs. freepages.min problem,
I propose we chose .low here since it's value is higher
and we're trying to solve a reliability problem here.
We'll find out what to do with the freepages.min once
we need it ... in 2.3 it _will_ be used.

regards,

Rik
--
The Internet is not a network of computers. It is a network
of people. That is its real strength.




--- linux-2.2.15-pre3/mm/vmscan.c.orig Wed Jan 19 21:18:54 2000
+++ linux-2.2.15-pre3/mm/vmscan.c Fri Jan 21 02:46:42 2000
@@ -485,18 +485,16 @@
* the processes needing more memory will wake us
* up on a more timely basis.
*/
- interruptible_sleep_on_timeout(&kswapd_wait, HZ);
while (nr_free_pages < freepages.high)
{
- if (do_try_to_free_pages(GFP_KSWAPD))
- {
- if (tsk->need_resched)
- schedule();
- continue;
- }
- tsk->state = TASK_INTERRUPTIBLE;
- schedule_timeout(10*HZ);
+ if (!do_try_to_free_pages(GFP_KSWAPD))
+ break;
+ if (tsk->need_resched)
+ schedule();
}
+ run_task_queue(&tq_disk);
+ tsk->state = TASK_INTERRUPTIBLE;
+ schedule_timeout(HZ);
}
}

@@ -509,18 +507,16 @@
* from user processes, because the locking issues are
* nasty to the extreme (file write locks, and MM locking)
*
- * One option might be to let kswapd do all the page-out
- * and VM page table scanning that needs locking, and this
- * process thread could do just the mmap shrink stage that
- * can be done by just dropping cached pages without having
- * any deadlock issues.
+ * If we're on or just slighly below freepages.low, kswapd
+ * should manage on its own, we just give it a nudge. This
+ * should also reduce contention for the kernel lock above.
*/
int try_to_free_pages(unsigned int gfp_mask)
{
int retval = 1;

wake_up_interruptible(&kswapd_wait);
- if (gfp_mask & __GFP_WAIT)
+ if ((gfp_mask & __GFP_WAIT) && (nr_free_pages < (freepages.low - 4)))
retval = do_try_to_free_pages(gfp_mask);
return retval;
}
--- linux-2.2.15-pre3/mm/page_alloc.c.orig Wed Jan 19 21:32:05 2000
+++ linux-2.2.15-pre3/mm/page_alloc.c Wed Jan 19 21:42:00 2000
@@ -212,7 +212,7 @@
if (!(current->flags & PF_MEMALLOC)) {
int freed;

- if (nr_free_pages > freepages.min) {
+ if (nr_free_pages > freepages.low) {
if (!low_on_memory)
goto ok_to_allocate;
if (nr_free_pages >= freepages.high) {

-
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