[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
[PATCH really] latency improvements, one reschedule moved
Again... :-(
Patch included this time...
/RogerL
Roger Larsson wrote:
>
> Hi Linus,
>
> Cleaned up and corrected some bugs...
> (memory_pressure... !
> unintended reschedule removed)
>
> Sadly the performance went down - slightly.
> Latency looks even nicer. Still some spikes.
> [sync and mmap002 behaviour not corrected]
>
> /RogerL
>
> Roger Larsson wrote:
> >
> > Hi Linus,
> >
> > [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/
> >
> > ------------------------------------------------------------------------
> > Name: patch-2.4.0-test3-pre2-vmscan.latency.2
> > patch-2.4.0-test3-pre2-vmscan.latency.2 Type: Plain Text (text/plain)
> > Encoding: 7bit
>
> --
> Home page:
> http://www.norran.net/nra02596/
> --
> To unsubscribe, send a message with 'unsubscribe linux-mm' in
> the body to majordomo@kvack.org. For more info on Linux MM,
> see: http://www.linux.eu.org/Linux-MM/
--
Home page:
http://www.norran.net/nra02596/
diff -aurp linux-2.4.0-test3-pre2/mm/vmscan.c linux/mm/vmscan.c
--- linux-2.4.0-test3-pre2/mm/vmscan.c Wed May 31 20:13:37 2000
+++ linux/mm/vmscan.c Wed Jul 5 00:52:59 2000
@@ -419,6 +419,48 @@ out:
}
/*
+ * 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.
@@ -442,11 +484,28 @@ static int do_try_to_free_pages(unsigned
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)) {
if (!--count)
goto done;
}
+ /* not (been) low on memory - it is
+ * pointless to try to swap out.
+ */
+ if (!keep_kswapd_awake())
+ goto done;
/* Try to get rid of some shared memory pages.. */
if (gfp_mask & __GFP_IO) {
@@ -457,8 +516,18 @@ static int do_try_to_free_pages(unsigned
*/
count -= shrink_dcache_memory(priority, gfp_mask);
count -= shrink_icache_memory(priority, gfp_mask);
- if (count <= 0)
- goto done;
+ /*
+ * Not currently working, see fixme in shrink_?cache_memory
+ * In the inner funtions there is a comment:
+ * "To help debugging, a zero exit status indicates
+ * all slabs were released." (-arca?)
+ * lets handle it in a primitive but working way...
+ * if (count <= 0)
+ * goto done;
+ */
+ if (!keep_kswapd_awake())
+ goto done;
+
while (shm_swap(priority, gfp_mask)) {
if (!--count)
goto done;
@@ -477,7 +546,8 @@ static int do_try_to_free_pages(unsigned
if (--swap_count < 0)
break;
- } while (--priority >= 0);
+ priority--;
+ } while (priority >= 0);
/* Always end on a shrink_mmap.. */
while (shrink_mmap(0, gfp_mask)) {
@@ -486,7 +556,7 @@ static int do_try_to_free_pages(unsigned
}
/* We return 1 if we are freed some page */
return (count != FREE_COUNT);
-
+
done:
return 1;
}
@@ -530,29 +600,14 @@ int kswapd(void *unused)
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()) {
+ /* wake up regulary to do an early attempt too free
+ * pages - pages will not actually be freed.
+ */
+ interruptible_sleep_on_timeout(&kswapd_wait, HZ);
}
+
+ do_try_to_free_pages(GFP_KSWAPD);
}
}
@@ -580,6 +635,12 @@ int try_to_free_pages(unsigned int gfp_m
retval = do_try_to_free_pages(gfp_mask);
current->flags &= ~PF_MEMALLOC;
}
+ else {
+ /* make sure kswapd runs */
+ if (waitqueue_active(&kswapd_wait))
+ wake_up_interruptible(&kswapd_wait);
+ }
+
return retval;
}