Hi,
[Intermediate release - indicator of problem with previous]
Since I am responsible for messing up some aspects of vm
(when fixing others)
here is a patch that tries to solve the introduced problems.
* no more periodic wake up of kswapd - not needed anymore
* no more freeing all zones to (free_pages > pages_high)
* always wakes kswapd up after try_to_free_pages
* kswapd starts when all zones gets zone_wake_kswapd
(runs once for each zone that hits zone_wake_kswapd)
* removed test for more than pages_high in alloc_pages,
zones will mostly be in the range [pages_high...pages_low]
* Up to 10% better throughput than 2.4.0-test4, YMMV
* Tested mostly with streaming tests. On a non HIGHMEM config.
+ New: zone_wake_kswapd == 2 indicates a situation where
free_pages < pages_low another alloc is done.
+ New-BUGFIX: runs kswapd while zone_wake_kswapd == 2 or
low_on_memory (Quintela)
+ New-BUGFIX? checks if __GFP_IO before rescheduling
(will become separate patch if correct, thanks Quintela)
- Kills mmap002, did not in the previously released that
should have this problem (but did not) - why? Will
investigate further...
- Since kswapd does not wake up periodic anymore, the
latencies might be worse... Will investigate it
further when other stuff works.
Note: logic of function keep_kswapd_awake has changed.
/RogerL
-- Home page: http://www.norran.net/nra02596/
--- linux/mm/vmscan.c.orig Sat Jul 15 23:44:34 2000 +++ linux/mm/vmscan.c Wed Jul 19 03:44:12 2000 @@ -419,7 +419,7 @@ out: } /* - * Check if there is any memory pressure (free_pages < pages_low) + * Check if there is any memory pressure (zone_wake_kswapd == 2) */ static inline int memory_pressure(void) { @@ -430,7 +430,7 @@ static inline int memory_pressure(void) for(i = 0; i < MAX_NR_ZONES; i++) { zone_t *zone = pgdat->node_zones+ i; if (zone->size && - zone->free_pages < zone->pages_low) + zone->zone_wake_kswapd == 2) return 1; } pgdat = pgdat->node_next; @@ -440,24 +440,31 @@ static inline int memory_pressure(void) } /* - * Check if there recently has been memory pressure (zone_wake_kswapd) + * Check if any zone have recently been critical (low_on_memory) + * any zone with current memory pressure (zone_wake_kswapd == 2) + * all zones have recently had memory_pressure (zone_wake_kswapd) */ static inline int keep_kswapd_awake(void) { + int all_recent = 1; 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; + if (!zone->size) { + if (zone->zone_wake_kswapd == 2 || + zone->low_on_memory) + return 1; + if (!zone->zone_wake_kswapd) + all_recent = 0; + } } pgdat = pgdat->node_next; } while (pgdat); - return 0; + return all_recent; } /* @@ -484,7 +491,7 @@ static int do_try_to_free_pages(unsigned priority = 64; do { - if (current->need_resched) { + if ((gfp_mask & __GFP_IO) && current->need_resched) { schedule(); /* time has passed - pressure too? */ if (!memory_pressure()) @@ -496,9 +503,7 @@ static int do_try_to_free_pages(unsigned goto done; } - /* not (been) low on memory - it is - * pointless to try to swap out. - */ + /* check if mission completed */ if (!keep_kswapd_awake()) goto done; @@ -596,10 +601,7 @@ int kswapd(void *unused) for (;;) { 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); + interruptible_sleep_on(&kswapd_wait); } do_try_to_free_pages(GFP_KSWAPD); @@ -628,24 +630,30 @@ int try_to_free_pages(unsigned int gfp_m if (gfp_mask & __GFP_WAIT) { current->state = TASK_RUNNING; current->flags |= PF_MEMALLOC; - retval = do_try_to_free_pages(gfp_mask); + do { + retval = do_try_to_free_pages(gfp_mask); + } while (!retval); current->flags &= ~PF_MEMALLOC; } - else { - /* make sure kswapd runs */ - if (waitqueue_active(&kswapd_wait)) - wake_up_interruptible(&kswapd_wait); - } + + /* someone needed memory that kswapd had not provided + * make sure kswapd runs, should not happen often */ + if (waitqueue_active(&kswapd_wait)) + wake_up_interruptible(&kswapd_wait); return retval; } static int __init kswapd_init(void) { - printk("Starting kswapd v1.6\n"); + printk("Starting kswapd v1.7\n"); swap_setup(); kernel_thread(kswapd, NULL, CLONE_FS | CLONE_FILES | CLONE_SIGHAND); return 0; } module_init(kswapd_init) + + + + --- linux/mm/page_alloc.c.orig Sat Jul 15 23:44:46 2000 +++ linux/mm/page_alloc.c Wed Jul 19 03:45:36 2000 @@ -141,9 +141,12 @@ void __free_pages_ok (struct page *page, spin_unlock_irqrestore(&zone->lock, flags); - if (zone->free_pages > zone->pages_high) { - zone->zone_wake_kswapd = 0; - zone->low_on_memory = 0; + if (zone->free_pages > zone->pages_low) { + zone->zone_wake_kswapd = 1; + if (zone->free_pages > zone->pages_high) { + zone->zone_wake_kswapd = 0; + zone->low_on_memory = 0; + } } } @@ -217,7 +220,7 @@ static struct page * rmqueue(zone_t *zon */ struct page * __alloc_pages(zonelist_t *zonelist, unsigned long order) { - zone_t **zone = zonelist->zones; + zone_t **zone; extern wait_queue_head_t kswapd_wait; /* @@ -228,21 +231,6 @@ struct page * __alloc_pages(zonelist_t * * in a higher zone fails. */ - for (;;) { - zone_t *z = *(zone++); - if (!z) - break; - if (!z->size) - BUG(); - - /* If there are zones with a lot of free memory allocate from them */ - if (z->free_pages > z->pages_high) { - struct page *page = rmqueue(z, order); - if (page) - return page; - } - } - zone = zonelist->zones; for (;;) { zone_t *z = *(zone++); @@ -256,6 +244,16 @@ struct page * __alloc_pages(zonelist_t * struct page *page = rmqueue(z, order); if (z->free_pages < z->pages_low) { z->zone_wake_kswapd = 1; + + /* Usually zone_wake_kswapd is set to 2 + * on second alloc below pages_low + * but if this was a big one + * - do not let it pass unnoticed + */ + if (z->free_pages < z->pages_low - MAX_ORDER) { + z->zone_wake_kswapd = 2; + } + if (waitqueue_active(&kswapd_wait)) wake_up_interruptible(&kswapd_wait); } @@ -264,6 +262,21 @@ struct page * __alloc_pages(zonelist_t * } } + /* Three possibilities to get here + * - Previous alloc_pages resulted in last zone set to have + * zone_wake_kswapd and start it. kswapd has not been able + * to release enough pages so that one zone does not have + * zone_wake_kswapd set. + * - Different sets of zones (zonelist) + * previous did not have all zones with zone_wake_kswapd but + * this one has... should kswapd be woken up? it will run once. + * - SMP race, kswapd went to sleep slightly after it as running + * in 'if (waitqueue_active(...))' above. + * + anyway the test is very cheap to do... + */ + if (waitqueue_active(&kswapd_wait)) + wake_up_interruptible(&kswapd_wait); + /* * Ok, we don't have any zones that don't need some * balancing.. See if we have any that aren't critical.. @@ -275,8 +288,17 @@ struct page * __alloc_pages(zonelist_t * break; if (!z->low_on_memory) { struct page *page = rmqueue(z, order); - if (z->free_pages < z->pages_min) - z->low_on_memory = 1; + if (z->free_pages < z->pages_low) { + z->zone_wake_kswapd = 2; /* future: ++ */ + + if (z->free_pages < z->pages_min) + z->low_on_memory = 1; + + /* make kswapd notice new condition */ + if (waitqueue_active(&kswapd_wait)) + wake_up_interruptible(&kswapd_wait); + } + if (page) return page; }
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This archive was generated by hypermail 2b29 : Sun Jul 23 2000 - 21:00:12 EST