Hi Linus,
here's a patch against 2.3.99-pre6 that fixes the stability problem
(apparently it was possible for a process to "slip through" the
tests in swap_out() and end up with a swap_cnt of 0 which would mean
an infinite loop in the leftshifting loop).
It also fixes a correctness issue in kswapd. Kswapd would exit
after one call to do_try_to_free_pages(), even if there was still
a lot of work to do. Now kswapd will play again if there are still
a lot of pages to free.
The performance problem isn't 100% fixed yet, but the other two
things are important enough that I thought I'd send the patch
now instead of after the (extra long) weekend.
regards,
Rik
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--- linux-2.3.99-pre6/mm/filemap.c.orig Thu Apr 27 12:49:05 2000 +++ linux-2.3.99-pre6/mm/filemap.c Fri Apr 28 19:49:01 2000 @@ -238,14 +238,13 @@ int shrink_mmap(int priority, int gfp_mask, zone_t *zone) { - int ret = 0, loop = 0, count; + int ret = 0, count; LIST_HEAD(young); LIST_HEAD(old); LIST_HEAD(forget); struct list_head * page_lru, * dispose; struct page * page = NULL; struct zone_struct * p_zone; - int maxloop = 256 >> priority; if (!zone) BUG(); @@ -262,30 +261,26 @@ list_del(page_lru); p_zone = page->zone; - /* - * These two tests are there to make sure we don't free too - * many pages from the "wrong" zone. We free some anyway, - * they are the least recently used pages in the system. - * When we don't free them, leave them in &old. - */ - dispose = &old; - if (p_zone != zone && (loop > (maxloop / 4) || - p_zone->free_pages > p_zone->pages_high)) - goto dispose_continue; + /* This LRU list only contains a few pages from the system, + * so we must fail and let swap_out() refill the list if + * there aren't enough freeable pages on the list */ /* The page is in use, or was used very recently, put it in * &young to make sure that we won't try to free it the next * time */ dispose = &young; - if (test_and_clear_bit(PG_referenced, &page->flags)) goto dispose_continue; - count--; + if (p_zone->free_pages > p_zone->pages_high) + goto dispose_continue; + if (!page->buffers && page_count(page) > 1) goto dispose_continue; - /* Page not used -> free it; if that fails -> &old */ + count--; + /* Page not used -> free it or put it on the old list + * so it gets freed first the next time */ dispose = &old; if (TryLockPage(page)) goto dispose_continue; @@ -375,9 +370,8 @@ /* nr_lru_pages needs the spinlock */ nr_lru_pages--; - loop++; /* wrong zone? not looped too often? roll again... */ - if (page->zone != zone && loop < maxloop) + if (page->zone != zone && count) goto again; out: --- linux-2.3.99-pre6/mm/page_alloc.c.orig Thu Apr 27 12:57:20 2000 +++ linux-2.3.99-pre6/mm/page_alloc.c Fri Apr 28 12:29:08 2000 @@ -285,9 +285,11 @@ goto allocate_ok; /* If we're a memory hog, unmap some pages */ - if (current->hog && low_on_memory && - (gfp_mask & __GFP_WAIT)) - swap_out(4, gfp_mask); + if (current->hog && low_on_memory && (gfp_mask & __GFP_WAIT)) { + // swap_out(6, gfp_mask); + // shm_swap(6, gfp_mask, (zone_t *)(zone)); + try_to_free_pages(gfp_mask, (zone_t *)(zone)); + } /* * (If anyone calls gfp from interrupts nonatomically then it --- linux-2.3.99-pre6/mm/vmscan.c.orig Thu Apr 27 12:57:58 2000 +++ linux-2.3.99-pre6/mm/vmscan.c Fri Apr 28 19:43:37 2000 @@ -387,8 +387,8 @@ if (!p->swappable || !mm || mm->rss <= 0) continue; /* small processes are swapped out less */ - while ((mm->swap_cnt << 2 * (i + 1) < max_cnt)) - i++; + while ((mm->swap_cnt << 2 * (i + 1) < max_cnt) + && i++ < 10) mm->swap_cnt >>= i; mm->swap_cnt += i; /* if swap_cnt reaches 0 */ /* we're big -> hog treatment */ @@ -437,14 +437,13 @@ { int priority; int count = SWAP_CLUSTER_MAX; - int ret; /* Always trim SLAB caches when memory gets low. */ kmem_cache_reap(gfp_mask); priority = 6; do { - while ((ret = shrink_mmap(priority, gfp_mask, zone))) { + while (shrink_mmap(priority, gfp_mask, zone)) { if (!--count) goto done; } @@ -467,9 +466,7 @@ } } - /* Then, try to page stuff out.. - * We use swapcount here because this doesn't actually - * free pages */ + /* Then, try to page stuff out.. */ while (swap_out(priority, gfp_mask)) { if (!--count) goto done; @@ -530,12 +527,16 @@ pgdat = pgdat_list; while (pgdat) { for (i = 0; i < MAX_NR_ZONES; i++) { - zone = pgdat->node_zones + i; + int count = SWAP_CLUSTER_MAX; + zone = pgdat->node_zones + i; + do { if (tsk->need_resched) schedule(); if ((!zone->size) || (!zone->zone_wake_kswapd)) continue; do_try_to_free_pages(GFP_KSWAPD, zone); + } while (zone->free_pages < zone->pages_low && + --count); } pgdat = pgdat->node_next; }
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This archive was generated by hypermail 2b29 : Sun Apr 30 2000 - 21:00:16 EST