by Mike Galbraith

[permalink] [raw]

On Thu, 19 Jul 2001, Linus Torvalds wrote:

>
> On Thu, 19 Jul 2001, Marcelo Tosatti wrote:
> >
> > Well, here is a patch on top of -ac5 (which already includes the first
> > zoned based approach patch).
>
> Looks ok.
>
> I'd like to see what the patch looks on top of a virgin tree, as it should
> now be noticeably smaller (no need to pas extra parameters etc).
>
> > I changed inactive_plenty() to use "zone->size / 3" instead "zone->size /
> > 2".
> >
> > Under _my_ tests using half of the perzone total pages as the inactive
> > target was too high.
>
> This is one of the reasons I'd like to see the virtgin patch - if the "/2"
> is too high, then that should mean that the behaviour is basically
> unchanged from before, right?

Under normal balance conditions (ie not zone specific shortage), yes, the
behaviour of swap_out() is the same.

But refill_inactive_scan() is not the same: Now we'll _never_ have any
zone with more than 1/3 of its "lruable" pages on the inactive lists due
to the "unlimited" background aging. That is a good thing, of course.

> Which would be a good sign that this kicks in gently - and I agree
> that "/3" sounds saner (or even "/4" - but we should double-check that
> the global inactive function is guaranteed to never trigger with all
> zones close to the "/4" target if so).

Well, under my heavy VM tests on highmem machines this test does trigger
quite often, which is expected.

Here it goes. (against pre9)

diff --exclude-from=/home/marcelo/exclude -Nur linux.orig/include/linux/swap.h linux/include/linux/swap.h
--- linux.orig/include/linux/swap.h Sat Jul 21 01:06:53 2001
+++ linux/include/linux/swap.h Sat Jul 21 01:16:59 2001
@@ -121,9 +121,15 @@
extern wait_queue_head_t kreclaimd_wait;
extern int page_launder(int, int);
extern int free_shortage(void);
+extern int total_free_shortage(void);
extern int inactive_shortage(void);
+extern int total_inactive_shortage(void);
extern void wakeup_kswapd(void);
extern int try_to_free_pages(unsigned int gfp_mask);
+
+extern unsigned int zone_free_shortage(zone_t *zone);
+extern unsigned int zone_inactive_shortage(zone_t *zone);
+extern unsigned int zone_inactive_plenty(zone_t *zone);

/* linux/mm/page_io.c */
extern void rw_swap_page(int, struct page *);
diff --exclude-from=/home/marcelo/exclude -Nur linux.orig/mm/page_alloc.c linux/mm/page_alloc.c
--- linux.orig/mm/page_alloc.c Sat Jul 21 01:06:53 2001
+++ linux/mm/page_alloc.c Sat Jul 21 01:11:32 2001
@@ -448,7 +448,7 @@
* to give up than to deadlock the kernel looping here.
*/
if (gfp_mask & __GFP_WAIT) {
- if (!order || free_shortage()) {
+ if (!order || total_free_shortage()) {
int progress = try_to_free_pages(gfp_mask);
if (progress || (gfp_mask & __GFP_FS))
goto try_again;
@@ -621,6 +621,53 @@
return pages;
}
#endif
+
+unsigned int zone_free_shortage(zone_t *zone)
+{
+ int sum = 0;
+
+ if (!zone->size)
+ goto ret;
+
+ if (zone->inactive_clean_pages + zone->free_pages
+ < zone->pages_min) {
+ sum += zone->pages_min;
+ sum -= zone->free_pages;
+ sum -= zone->inactive_clean_pages;
+ }
+ret:
+ return sum;
+}
+
+unsigned int zone_inactive_plenty(zone_t *zone)
+{
+ int inactive;
+
+ if (!zone->size)
+ return 0;
+
+ inactive = zone->inactive_dirty_pages;
+ inactive += zone->inactive_clean_pages;
+ inactive += zone->free_pages;
+
+ return (inactive > (zone->size / 3));
+
+}
+unsigned int zone_inactive_shortage(zone_t *zone)
+{
+ int sum = 0;
+
+ if (!zone->size)
+ goto ret;
+
+ sum = zone->pages_high;
+ sum -= zone->inactive_dirty_pages;
+ sum -= zone->inactive_clean_pages;
+ sum -= zone->free_pages;
+
+ret:
+ return (sum > 0 ? sum : 0);
+}

/*
* Show free area list (used inside shift_scroll-lock stuff)
diff --exclude-from=/home/marcelo/exclude -Nur linux.orig/mm/vmscan.c linux/mm/vmscan.c
--- linux.orig/mm/vmscan.c Sat Jul 21 01:06:53 2001
+++ linux/mm/vmscan.c Sat Jul 21 01:24:33 2001
@@ -41,6 +41,14 @@
pte_t pte;
swp_entry_t entry;

+ /*
+ * If we are doing a zone-specific scan, do not
+ * touch pages from zones which don't have a
+ * shortage.
+ */
+ if (zone_inactive_plenty(page->zone))
+ return;
+
/* Don't look at this pte if it's been accessed recently. */
if (ptep_test_and_clear_young(page_table)) {
page->age += PAGE_AGE_ADV;
@@ -426,7 +434,7 @@
#define MAX_LAUNDER (4 * (1 << page_cluster))
#define CAN_DO_FS (gfp_mask & __GFP_FS)
#define CAN_DO_IO (gfp_mask & __GFP_IO)
-int page_launder(int gfp_mask, int sync)
+int do_page_launder(zone_t *zone, int gfp_mask, int sync)
{
int launder_loop, maxscan, cleaned_pages, maxlaunder;
struct list_head * page_lru;
@@ -461,6 +469,17 @@
continue;
}

+ /*
+ * If we are doing zone-specific laundering,
+ * avoid touching pages from zones which do
+ * not have a free shortage.
+ */
+ if (zone && !zone_free_shortage(page->zone)) {
+ list_del(page_lru);
+ list_add(page_lru, &inactive_dirty_list);
+ continue;
+ }
+
/*
* The page is locked. IO in progress?
* Move it to the back of the list.
@@ -574,8 +593,13 @@
* If we're freeing buffer cache pages, stop when
* we've got enough free memory.
*/
- if (freed_page && !free_shortage())
- break;
+ if (freed_page) {
+ if (zone) {
+ if (!zone_free_shortage(zone))
+ break;
+ } else if (!free_shortage())
+ break;
+ }
continue;
} else if (page->mapping && !PageDirty(page)) {
/*
@@ -613,7 +637,7 @@
* loads, flush out the dirty pages before we have to wait on
* IO.
*/
- if (CAN_DO_IO && !launder_loop && free_shortage()) {
+ if (CAN_DO_IO && !launder_loop && total_free_shortage()) {
launder_loop = 1;
/* If we cleaned pages, never do synchronous IO. */
if (cleaned_pages)
@@ -629,6 +653,33 @@
return cleaned_pages;
}

+int page_launder(int gfp_mask, int sync)
+{
+ int type = 0, ret = 0;
+ pg_data_t *pgdat = pgdat_list;
+ /*
+ * First do a global scan if there is a
+ * global shortage.
+ */
+ if (free_shortage())
+ ret += do_page_launder(NULL, gfp_mask, sync);
+
+ /*
+ * Then check if there is any specific zone
+ * needs laundering.
+ */
+ for (type = 0; type < MAX_NR_ZONES; type++) {
+ zone_t *zone = pgdat->node_zones + type;
+
+ if (zone_free_shortage(zone))
+ ret += do_page_launder(zone, gfp_mask, sync);
+ }
+
+ return ret;
+}
+
+
+
/**
* refill_inactive_scan - scan the active list and find pages to deactivate
* @priority: the priority at which to scan
@@ -637,7 +688,7 @@
* This function will scan a portion of the active list to find
* unused pages, those pages will then be moved to the inactive list.
*/
-int refill_inactive_scan(unsigned int priority, int target)
+int refill_inactive_scan(zone_t *zone, unsigned int priority, int target)
{
struct list_head * page_lru;
struct page * page;
@@ -665,6 +716,16 @@
continue;
}

+ /*
+ * Do not deactivate pages from zones which
+ * have plenty inactive pages.
+ */
+
+ if (zone_inactive_plenty(page->zone)) {
+ page_active = 1;
+ goto skip_page;
+ }
+
/* Do aging on the pages. */
if (PageTestandClearReferenced(page)) {
age_page_up_nolock(page);
@@ -695,10 +756,12 @@
* we have done enough work.
*/
if (page_active || PageActive(page)) {
+skip_page:
list_del(page_lru);
list_add(page_lru, &active_list);
} else {
- nr_deactivated++;
+ if (!zone || (zone && (zone == page->zone)))
+ nr_deactivated++;
if (target && nr_deactivated >= target)
break;
}
@@ -709,19 +772,32 @@
}

/*
- * Check if there are zones with a severe shortage of free pages,
- * or if all zones have a minor shortage.
+ * Check if we have are low on free pages globally.
*/
int free_shortage(void)
{
- pg_data_t *pgdat = pgdat_list;
- int sum = 0;
int freeable = nr_free_pages() + nr_inactive_clean_pages();
int freetarget = freepages.high;

/* Are we low on free pages globally? */
if (freeable < freetarget)
return freetarget - freeable;
+ return 0;
+}
+
+/*
+ *
+ * Check if there are zones with a severe shortage of free pages,
+ * or if all zones have a minor shortage.
+ */
+int total_free_shortage(void)
+{
+ int sum = 0;
+ pg_data_t *pgdat = pgdat_list;
+
+ /* Do we have a global free shortage? */
+ if((sum = free_shortage()))
+ return sum;

/* If not, are we very low on any particular zone? */
do {
@@ -739,15 +815,15 @@
} while (pgdat);

return sum;
+
}

/*
- * How many inactive pages are we short?
+ * How many inactive pages are we short globally?
*/
int inactive_shortage(void)
{
int shortage = 0;
- pg_data_t *pgdat = pgdat_list;

/* Is the inactive dirty list too small? */

@@ -759,10 +835,20 @@

if (shortage > 0)
return shortage;
+ return 0;
+}
+/*
+ * Are we low on inactive pages globally or in any zone?
+ */
+int total_inactive_shortage(void)
+{
+ int shortage = 0;
+ pg_data_t *pgdat = pgdat_list;

- /* If not, do we have enough per-zone pages on the inactive list? */
+ if((shortage = inactive_shortage()))
+ return shortage;

- shortage = 0;
+ shortage = 0;

do {
int i;
@@ -802,7 +888,7 @@
* when called from a user process.
*/
#define DEF_PRIORITY (6)
-static int refill_inactive(unsigned int gfp_mask, int user)
+static int refill_inactive_global(unsigned int gfp_mask, int user)
{
int count, start_count, maxtry;

@@ -826,7 +912,7 @@
/* Walk the VM space for a bit.. */
swap_out(DEF_PRIORITY, gfp_mask);

- count -= refill_inactive_scan(DEF_PRIORITY, count);
+ count -= refill_inactive_scan(NULL, DEF_PRIORITY, count);
if (count <= 0)
goto done;

@@ -839,6 +925,59 @@
return (count < start_count);
}

+static int refill_inactive_zone(zone_t *zone, unsigned int gfp_mask, int user)
+{
+ int count, start_count, maxtry;
+
+ count = start_count = zone_inactive_shortage(zone);
+
+ maxtry = (1 << DEF_PRIORITY);
+
+ do {
+ swap_out(DEF_PRIORITY, gfp_mask);
+
+ count -= refill_inactive_scan(zone, DEF_PRIORITY, count);
+
+ if (count <= 0)
+ goto done;
+
+ if (--maxtry <= 0)
+ return 0;
+
+ } while(zone_inactive_shortage(zone));
+done:
+ return (count < start_count);
+}
+
+
+static int refill_inactive(unsigned int gfp_mask, int user)
+{
+ int type = 0, ret = 0;
+ pg_data_t *pgdat = pgdat_list;
+ /*
+ * First do a global scan if there is a
+ * global shortage.
+ */
+ if (inactive_shortage())
+ ret += refill_inactive_global(gfp_mask, user);
+
+ /*
+ * Then check if there is any specific zone
+ * with a shortage and try to refill it if
+ * so.
+ */
+ for (type = 0; type < MAX_NR_ZONES; type++) {
+ zone_t *zone = pgdat->node_zones + type;
+
+ if (zone_inactive_shortage(zone))
+ ret += refill_inactive_zone(zone, gfp_mask, user);
+ }
+
+ return ret;
+}
+
+#define DEF_PRIORITY (6)
+
static int do_try_to_free_pages(unsigned int gfp_mask, int user)
{
int ret = 0;
@@ -851,8 +990,10 @@
* before we get around to moving them to the other
* list, so this is a relatively cheap operation.
*/
- if (free_shortage()) {
- ret += page_launder(gfp_mask, user);
+
+ ret += page_launder(gfp_mask, user);
+
+ if (total_free_shortage()) {
shrink_dcache_memory(DEF_PRIORITY, gfp_mask);
shrink_icache_memory(DEF_PRIORITY, gfp_mask);
}
@@ -861,8 +1002,7 @@
* If needed, we move pages from the active list
* to the inactive list.
*/
- if (inactive_shortage())
- ret += refill_inactive(gfp_mask, user);
+ ret += refill_inactive(gfp_mask, user);

/*
* Reclaim unused slab cache if memory is low.
@@ -917,7 +1057,7 @@
static long recalc = 0;

/* If needed, try to free some memory. */
- if (inactive_shortage() || free_shortage())
+ if (total_inactive_shortage() || total_free_shortage())
do_try_to_free_pages(GFP_KSWAPD, 0);

/* Once a second ... */
@@ -928,7 +1068,7 @@
recalculate_vm_stats();

/* Do background page aging. */
- refill_inactive_scan(DEF_PRIORITY, 0);
+ refill_inactive_scan(NULL, DEF_PRIORITY, 0);
}

run_task_queue(&tq_disk);
@@ -944,7 +1084,7 @@
* We go to sleep for one second, but if it's needed
* we'll be woken up earlier...
*/
- if (!free_shortage() || !inactive_shortage()) {
+ if (!total_free_shortage() || !total_inactive_shortage()) {
interruptible_sleep_on_timeout(&kswapd_wait, HZ);
/*
* If we couldn't free enough memory, we see if it was