From: Rik van Riel Track non-resident pages through a simple hashing scheme. This way the space overhead is limited to 1 u32 per page, or 0.1% space overhead and lookups are one cache miss. Aside from seeing whether or not a page was recently evicted, we can also take a reasonable guess at how many other pages were evicted since this page was evicted. TODO: make the entries unsigned long, currently we're limited to 1^32*NUM_NR*PAGE_SIZE bytes of memory. Event though this would end up being 1008 TB of memory, I suspect the hash function to go crap at around 4 to 16 TB. Signed-off-by: Rik van Riel Signed-off-by: Peter Zijlstra --- Documentation/kernel-parameters.txt | 4 include/linux/nonresident.h | 35 +++++++ init/main.c | 2 mm/Kconfig | 4 mm/Makefile | 1 mm/nonresident.c | 173 ++++++++++++++++++++++++++++++++++++ mm/swap.c | 3 mm/vmscan.c | 3 8 files changed, 225 insertions(+) Index: linux-2.6/mm/nonresident.c =================================================================== --- /dev/null +++ linux-2.6/mm/nonresident.c @@ -0,0 +1,173 @@ +/* + * mm/nonresident.c + * (C) 2004,2005 Red Hat, Inc + * Written by Rik van Riel + * Released under the GPL, see the file COPYING for details. + * + * Keeps track of whether a non-resident page was recently evicted + * and should be immediately promoted to the active list. This also + * helps automatically tune the inactive target. + * + * The pageout code stores a recently evicted page in this cache + * by calling remember_page(mapping/mm, index/vaddr, generation) + * and can look it up in the cache by calling recently_evicted() + * with the same arguments. + * + * Note that there is no way to invalidate pages after eg. truncate + * or exit, we let the pages fall out of the non-resident set through + * normal replacement. + */ +#include +#include +#include +#include +#include +#include +#include + +/* Number of non-resident pages per hash bucket. Never smaller than 15. */ +#if (L1_CACHE_BYTES < 64) +#define NR_BUCKET_BYTES 64 +#else +#define NR_BUCKET_BYTES L1_CACHE_BYTES +#endif +#define NUM_NR ((NR_BUCKET_BYTES - sizeof(atomic_t))/sizeof(atomic_t)) + +struct nr_bucket +{ + atomic_t hand; + atomic_t cookie[NUM_NR]; +} ____cacheline_aligned; + +/* The non-resident page hash table. */ +static struct nr_bucket *nonres_table; +static unsigned int nonres_shift; +static unsigned int nonres_mask; + +static struct nr_bucket *nr_hash(void *mapping, unsigned long index) +{ + unsigned long bucket; + unsigned long hash; + + hash = hash_ptr(mapping, BITS_PER_LONG); + hash = 37 * hash + hash_long(index, BITS_PER_LONG); + bucket = hash & nonres_mask; + + return nonres_table + bucket; +} + +static u32 nr_cookie(struct address_space *mapping, unsigned long index) +{ + unsigned long cookie; + + cookie = hash_ptr(mapping, BITS_PER_LONG); + cookie = 37 * cookie + hash_long(index, BITS_PER_LONG); + + if (mapping && mapping->host) { + cookie *= 37; + cookie += hash_long(mapping->host->i_ino, BITS_PER_LONG); + } + + return (u32)(cookie >> (BITS_PER_LONG - 32)); +} + +unsigned long +nonresident_get(struct address_space *mapping, unsigned long index) +{ + struct nr_bucket *bucket; + unsigned long distance = ~0UL; + u32 wanted; + int i; + + if (!mapping) + return distance; + + prefetch(mapping->host); + bucket = nr_hash(mapping, index); + + prefetch(bucket); + wanted = nr_cookie(mapping, index); + + for (i = 0; i < NUM_NR; i++) { + if ((u32)atomic_cmpxchg(&bucket->cookie[i], wanted, 0) == wanted) { + /* Return the distance between entry and clock hand. */ + distance = atomic_read(&bucket->hand) + NUM_NR - i; + distance %= NUM_NR; + distance += (bucket - nonres_table); + goto out; + } + } + +out: + return distance; +} + +u32 nonresident_put(struct address_space *mapping, unsigned long index) +{ + struct nr_bucket *bucket; + u32 cookie; + int cur_hand; + int hand; + + prefetch(mapping->host); + bucket = nr_hash(mapping, index); + + prefetchw(bucket); + cookie = nr_cookie(mapping, index); + + /* Atomically find the next array index. */ + do { + cur_hand = atomic_read(&bucket->hand); + hand = cur_hand + 1; + if (unlikely(hand == NUM_NR)) + hand = 0; + } while (atomic_cmpxchg(&bucket->hand, cur_hand, hand) != cur_hand); + + /* Statistics may want to know whether the entry was in use. */ + return atomic_xchg(&bucket->cookie[hand], cookie); +} + +unsigned long nonresident_total(void) +{ + return NUM_NR << nonres_shift; +} + +/* + * For interactive workloads, we remember about as many non-resident pages + * as we have actual memory pages. For server workloads with large inter- + * reference distances we could benefit from remembering more. + */ +static __initdata unsigned long nonresident_factor = 100; +void __init nonresident_init(void) +{ + int target; + int i; + + /* + * Calculate the non-resident hash bucket target. Use a power of + * two for the division because alloc_large_system_hash rounds up. + */ + target = (nr_all_pages * nonresident_factor) / 100; + target /= (sizeof(struct nr_bucket) / sizeof(atomic_t)); + + nonres_table = alloc_large_system_hash("Non-resident page tracking", + sizeof(struct nr_bucket), + target, + 0, + HASH_EARLY, + &nonres_shift, + &nonres_mask, + 0); + + for (i = 0; i < (1 << nonres_shift); i++) + atomic_set(&nonres_table[i].hand, 0); +} + +static int __init set_nonresident_factor(char *str) +{ + if (!str) + return 0; + nonresident_factor = simple_strtoul(str, &str, 0); + return 1; +} +__setup("nonresident_factor=", set_nonresident_factor); Index: linux-2.6/include/linux/nonresident.h =================================================================== --- /dev/null +++ linux-2.6/include/linux/nonresident.h @@ -0,0 +1,35 @@ +#ifndef _LINUX_NONRESIDENT_H_ +#define _LINUX_NONRESIDENT_H_ + +#ifdef __KERNEL__ + +#ifdef CONFIG_MM_NONRESIDENT + +extern void nonresident_init(void); +extern unsigned long nonresident_get(struct address_space *, unsigned long); +extern u32 nonresident_put(struct address_space *, unsigned long); +extern unsigned long nonresident_total(void); + +#else /* CONFIG_MM_NONRESIDENT */ + +static inline void nonresident_init(void) { } +static inline +unsigned long nonresident_get(struct address_space *, unsigned long, int) +{ + return 0; +} + +static inline u32 nonresident_put(struct address_space *, unsigned long) +{ + return 0; +} + +static inline unsigned long nonresident_total(void) +{ + return 0; +} + +#endif /* CONFIG_MM_NONRESIDENT */ + +#endif /* __KERNEL */ +#endif /* _LINUX_NONRESIDENT_H_ */ Index: linux-2.6/init/main.c =================================================================== --- linux-2.6.orig/init/main.c +++ linux-2.6/init/main.c @@ -55,6 +55,7 @@ #include #include #include +#include #include #include @@ -611,6 +612,7 @@ asmlinkage void __init start_kernel(void #endif vfs_caches_init_early(); cpuset_init_early(); + nonresident_init(); mem_init(); kmem_cache_init(); setup_per_cpu_pageset(); Index: linux-2.6/mm/Makefile =================================================================== --- linux-2.6.orig/mm/Makefile +++ linux-2.6/mm/Makefile @@ -15,6 +15,7 @@ obj-y := bootmem.o filemap.o mempool.o obj-$(CONFIG_BOUNCE) += bounce.o obj-$(CONFIG_SWAP) += page_io.o swap_state.o swapfile.o thrash.o +obj-$(CONFIG_MM_NONRESIDENT) += nonresident.o obj-$(CONFIG_HUGETLBFS) += hugetlb.o obj-$(CONFIG_NUMA) += mempolicy.o obj-$(CONFIG_SPARSEMEM) += sparse.o Index: linux-2.6/mm/swap.c =================================================================== --- linux-2.6.orig/mm/swap.c +++ linux-2.6/mm/swap.c @@ -30,6 +30,7 @@ #include #include #include +#include /* How many pages do we try to swap or page in/out together? */ int page_cluster; @@ -365,6 +366,7 @@ void __pagevec_lru_add(struct pagevec *p } VM_BUG_ON(PageLRU(page)); SetPageLRU(page); + nonresident_get(page_mapping(page), page_index(page)); add_page_to_inactive_list(zone, page); } if (zone) @@ -392,6 +394,7 @@ void __pagevec_lru_add_active(struct pag } VM_BUG_ON(PageLRU(page)); SetPageLRU(page); + nonresident_get(page_mapping(page), page_index(page)); VM_BUG_ON(PageActive(page)); SetPageActive(page); add_page_to_active_list(zone, page); Index: linux-2.6/mm/vmscan.c =================================================================== --- linux-2.6.orig/mm/vmscan.c +++ linux-2.6/mm/vmscan.c @@ -37,6 +37,7 @@ #include #include #include +#include #include #include @@ -402,6 +403,7 @@ int remove_mapping(struct address_space if (PageSwapCache(page)) { swp_entry_t swap = { .val = page_private(page) }; + nonresident_put(mapping, page_index(page)); __delete_from_swap_cache(page); write_unlock_irq(&mapping->tree_lock); swap_free(swap); @@ -409,6 +411,7 @@ int remove_mapping(struct address_space return 1; } + nonresident_put(mapping, page_index(page)); __remove_from_page_cache(page); write_unlock_irq(&mapping->tree_lock); __put_page(page); Index: linux-2.6/mm/Kconfig =================================================================== --- linux-2.6.orig/mm/Kconfig +++ linux-2.6/mm/Kconfig @@ -158,6 +158,10 @@ config RESOURCES_64BIT help This option allows memory and IO resources to be 64 bit. +config MM_NONRESIDENT + bool "Track nonresident pages" + def_bool y + config ZONE_DMA_FLAG int default "0" if !ZONE_DMA Index: linux-2.6/Documentation/kernel-parameters.txt =================================================================== --- linux-2.6.orig/Documentation/kernel-parameters.txt +++ linux-2.6/Documentation/kernel-parameters.txt @@ -1167,6 +1167,10 @@ and is between 256 and 4096 characters. nomce [IA-32] Machine Check Exception + nonresident_factor= [KNL] Scale the size of the nonresident history + The default is 100, which equals the total + memory size. + noreplace-paravirt [IA-32,PV_OPS] Don't patch paravirt_ops noreplace-smp [IA-32,SMP] Don't replace SMP instructions -- - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/