Linux-kernel mailing list archive 2000-23,: Re: [uPatch] Re: Graceful failure?

# Re: [uPatch] Re: Graceful failure?

John Fremlin (vii@penguinpowered.com)
05 Jun 2000 21:21:25 +0100

- Messages sorted by: [ date ][ thread ][ subject ][ author ]
- Next message: Stephen Frost: "Re: ULTRA ATA/100 announced"
- Previous message: Roeland Th. Jansen: "TLB IPI wait/oops"
- In reply to: Rik van Riel: "[uPatch] Re: Graceful failure?"

Rik van Riel <riel@conectiva.com.br> writes:

> On Mon, 5 Jun 2000, Billy Harvey wrote:
>
> > A "make -j" slowly over the course of 5 minutes drives the load
> > to about 30. At first the degradation is controlled, with
> > sendmail refusing service, but at about 160 process visible in
> > top, top quits updating (set a 8 second updates), showing about
> > 2 MB swap used. At this point it sounds like the system is
> > thrashing.
>
> That probably means you're a lot more in swap now and top
> has stopped displaying before you really hit the swap...

Allow me to hype my patch again. Could someone please test it?

It improves performance markedly (no horrible pauses in
vmscan.c:swap_out under heavy load).

>
> > Is this failure process acceptable? I'd think the system should
> > react differently to the thrashing, killing off the load
> > demanding user process(es), rather than degrading to a point of
> > freeze.

My patch fixes this for me, please test.

[...]

--- linux-2.4.0t1a7m3/mm/vmscan.c Sat Jun 3 17:10:15 2000
+++ kernel-hacking/mm/vmscan.c Sun Jun 4 16:35:31 2000
@@ -361,23 +361,24 @@
/*
* We make one or two passes through the task list, indexed by
* assign = {0, 1}:
- * Pass 1: select the swappable task with maximal RSS that has
- * not yet been swapped out.
+ *
+ * Pass 1: select the first swappable task that has not yet
+ * been swapped out.
+ *
* Pass 2: re-assign rss swap_cnt values, then select as above.
*
* With this approach, there's no need to remember the last task
* swapped out. If the swap-out fails, we clear swap_cnt so the
* task won't be selected again until all others have been tried.
*
- * Think of swap_cnt as a "shadow rss" - it tells us which process
- * we want to page out (always try largest first).
- */
+ * Think of swap_cnt as a "shadow rss" - it tells us which
+ * process we want to page out (always try largest first). */
+
counter = (nr_threads << 2) >> (priority >> 2);
if (counter < 1)
counter = 1;
for (; counter >= 0; counter--) {
- unsigned long max_cnt = 0;
struct mm_struct *best = NULL;
int pid = 0;
int assign = 0;
@@ -391,13 +392,14 @@
if (mm->rss <= 0)
continue;
/* Refresh swap_cnt? */
- if (assign == 1)
+ best = mm;
+ pid = p->pid;
+
+ if (assign == 1){
mm->swap_cnt = mm->rss;
- if (mm->swap_cnt > max_cnt) {
- max_cnt = mm->swap_cnt;
- best = mm;
- pid = p->pid;
}
+ else
+ break;
}
read_unlock(&tasklist_lock);
if (!best) {

    --

    	http://altern.org/vii

    -
    To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
    the body of a message to majordomo@vger.rutgers.edu
    Please read the FAQ at http://www.tux.org/lkml/

- Next message: Stephen Frost: "Re: ULTRA ATA/100 announced"
- Previous message: Roeland Th. Jansen: "TLB IPI wait/oops"
- In reply to: Rik van Riel: "[uPatch] Re: Graceful failure?"