Hi Linus, Paul, Benno, ...,
[patch against linux-2.4.0-test3-pre2]
I cleaned up kswapd and moved its reschedule point.
Disk performance is close to the same.
Latencies have improved a lot (tested with Bennos latencytest)
* sync is still problematic
* mmap002 (Quintinela) still gives a 212 ms latency
(compared to 423 ms for the unpatched...)
* other disk related latencies are down under 30 ms.
(streaming read, copy, write)
* the number of overruns has dropped considerably!
(running 4 buffers with a deadline of 23 ms)
/RogerL
--
Home page:
http://www.norran.net/nra02596/
--- linux/mm/vmscan.c.orig Wed May 31 20:13:37 2000
+++ linux/mm/vmscan.c Sat Jul 1 03:29:00 2000
@@ -419,6 +419,48 @@
}
/*
+ * Check if there is any memory pressure (free_pages < pages_low)
+ */
+static inline int memory_pressure(void)
+{
+ pg_data_t *pgdat = pgdat_list;
+
+ do {
+ int i;
+ for(i = 0; i < MAX_NR_ZONES; i++) {
+ zone_t *zone = pgdat->node_zones+ i;
+ if (!zone->size &&
+ zone->free_pages < zone->pages_low)
+ return 1;
+ }
+ pgdat = pgdat->node_next;
+ } while (pgdat);
+
+ return 0;
+}
+
+/*
+ * Check if there is any memory pressure (free_pages < pages_low)
+ */
+static inline int keep_kswapd_awake(void)
+{
+ pg_data_t *pgdat = pgdat_list;
+
+ do {
+ int i;
+ for(i = 0; i < MAX_NR_ZONES; i++) {
+ zone_t *zone = pgdat->node_zones+ i;
+ if (!zone->size &&
+ zone->zone_wake_kswapd)
+ return 1;
+ }
+ pgdat = pgdat->node_next;
+ } while (pgdat);
+
+ return 0;
+}
+
+/*
* We need to make the locks finer granularity, but right
* now we need this so that we can do page allocations
* without holding the kernel lock etc.
@@ -442,7 +484,20 @@
priority = 64;
do {
+ /* should __GFP_WAIT be checked?
+ * assume not - not WAITING for a free page
+ * let more important task execute before
+ * continuing (Note: kswapd does not use it).
+ */
+ if (current->need_resched) {
+ schedule();
+ /* time has passed - pressure too? */
+ if (!memory_pressure())
+ goto done;
+ }
+
while (shrink_mmap(priority, gfp_mask)) {
+ /* check __GFP_WAIT ? see below */
if (!--count)
goto done;
}
@@ -477,16 +532,21 @@
if (--swap_count < 0)
break;
- } while (--priority >= 0);
+ priority--;
+ } while (priority >= 0);
/* Always end on a shrink_mmap.. */
while (shrink_mmap(0, gfp_mask)) {
+ if (current->need_resched)
+ schedule();
+ if (!memory_pressure())
+ return 1;
if (!--count)
goto done;
}
/* We return 1 if we are freed some page */
return (count != FREE_COUNT);
-
+
done:
return 1;
}
@@ -530,29 +590,12 @@
tsk->flags |= PF_MEMALLOC;
for (;;) {
- pg_data_t *pgdat;
- int something_to_do = 0;
-
- pgdat = pgdat_list;
- do {
- int i;
- for(i = 0; i < MAX_NR_ZONES; i++) {
- zone_t *zone = pgdat->node_zones+ i;
- if (tsk->need_resched)
- schedule();
- if (!zone->size || !zone->zone_wake_kswapd)
- continue;
- if (zone->free_pages < zone->pages_low)
- something_to_do = 1;
- do_try_to_free_pages(GFP_KSWAPD);
- }
- pgdat = pgdat->node_next;
- } while (pgdat);
-
- if (!something_to_do) {
- tsk->state = TASK_INTERRUPTIBLE;
- interruptible_sleep_on(&kswapd_wait);
+ if (!keep_kswapd_awake()) {
+ tsk->state = TASK_INTERRUPTIBLE;
+ interruptible_sleep_on(&kswapd_wait);
}
+
+ do_try_to_free_pages(GFP_KSWAPD);
}
}
