Basic infrastructure to track non-resident pages. This code is needed to support advanced page replacement algorithms like CLOCK-Pro or CART.
Note that this code could use an actual hash function. Links to the actual replacement algorithms can be found on: http://wiki.linux-mm.org/wiki/AdvancedPageReplacement Signed-off-by: Rik van Riel <[EMAIL PROTECTED]> --- linux-2.6.11/include/linux/nonresident.h.nonres 2005-04-22 17:19:20.000000000 -0400 +++ linux-2.6.11/include/linux/nonresident.h 2005-04-22 17:20:31.000000000 -0400 @@ -0,0 +1,11 @@ +/* + * include/linux/nonresident.h + * (C) 2004,2005 Red Hat, Inc + * Written by Rik van Riel <[EMAIL PROTECTED]> + * 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. + */ +extern int recently_evicted(void *, unsigned long, short); +extern int remember_page(void *, unsigned long, short); --- linux-2.6.11/mm/nonresident.c.nonres 2005-04-22 17:19:13.000000000 -0400 +++ linux-2.6.11/mm/nonresident.c 2005-04-22 17:21:12.000000000 -0400 @@ -0,0 +1,130 @@ +/* + * mm/nonresident.c + * (C) 2004,2005 Red Hat, Inc + * Written by Rik van Riel <[EMAIL PROTECTED]> + * 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, offset/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 <linux/mm.h> +#include <linux/cache.h> +#include <linux/spinlock.h> +#include <linux/bootmem.h> +#include <linux/jhash.h> +// #include <linux/nonresident.h> + +static unsigned long nr_buckets; + +/* + * We fold the object generation number into the offset field, since + * that one has the most "free" bits on a 32 bit system. + */ +#define NR_GEN_SHIFT (BITS_PER_LONG * 7 / 8) +#define NR_OFFSET_MASK ((1 << NR_GEN_SHIFT) - 1) +#define make_nr_oag(x,y) (((x) & NR_OFFSET_MASK) + ((y) << NR_GEN_SHIFT)) + +struct nr_page { + void * mapping; + unsigned long offset_and_gen; +}; + +/* Number of non-resident pages per hash bucket */ +#define NUM_NR ((L1_CACHE_BYTES - sizeof(spinlock_t))/sizeof(struct nr_page)) + +struct nr_bucket +{ + spinlock_t lock; + struct nr_page pages[NUM_NR]; +} ____cacheline_aligned; + +/* The non-resident page hash table. */ +static struct nr_bucket * nr_hashtable; + +/* Wanted: a real hash function for 2 longs. */ +struct nr_bucket * nr_hash(void * mapping, unsigned long offset_and_gen) +{ + unsigned long bucket; + bucket = ((unsigned long)mapping + offset_and_gen) % nr_buckets; + return nr_hashtable + bucket; +} + +static int nr_same(struct nr_page * first, struct nr_page * second) +{ + /* Chances are this nr_page belongs to a different mapping ... */ + if (first->mapping != second->mapping) + return 0; + + /* ... but if it matches the mapping, it's probably the same page. */ + if (likely(first->offset_and_gen == second->offset_and_gen)) + return 1; + + return 0; +} + +int recently_evicted(void * mapping, unsigned long offset, short gen) +{ + unsigned long offset_and_gen = make_nr_oag(offset, gen); + struct nr_bucket * nr_bucket = nr_hash(mapping, offset_and_gen); + struct nr_page wanted; + int state = -1; + int i; + + wanted.offset_and_gen = offset_and_gen; + wanted.mapping = mapping; + + spin_lock(&nr_bucket->lock); + for (i = 0; i < NUM_NR; i++) { + struct nr_page * found = &nr_bucket->pages[i]; + if (nr_same(found, &wanted)) { + found->mapping = 0; + state = 1; + } + } + spin_unlock(&nr_bucket->lock); + + return state; +} + +int remember_page(void * mapping, unsigned long offset, short gen) +{ + unsigned long offset_and_gen = make_nr_oag(offset, gen); + struct nr_bucket * nr_bucket = nr_hash(mapping, offset_and_gen); + struct nr_page * victim; + int recycled = 0; + int i; + + spin_lock(&nr_bucket->lock); + for (i = 0; i < NUM_NR; i++) { + victim = &nr_bucket->pages[i]; + if (victim->mapping == 0) + goto assign; + } + + /* Randomly recycle an nr_page. */ + i = (offset ^ jiffies) % NUM_NR; + victim = &nr_bucket->pages[i]; + recycled = 1; + +assign: + victim->mapping = mapping; + victim->offset_and_gen = offset_and_gen; + spin_unlock(&nr_bucket->lock); + return recycled; +} + +void __init init_nonresident(unsigned long mempages) +{ + nr_buckets = mempages / NUM_NR; + nr_hashtable = alloc_bootmem(nr_buckets * sizeof(struct nr_bucket)); +} --- linux-2.6.11/mm/Makefile.nonres 2005-04-22 17:19:49.000000000 -0400 +++ linux-2.6.11/mm/Makefile 2005-04-22 11:25:36.000000000 -0400 @@ -12,7 +12,8 @@ obj-y := bootmem.o filemap.o mempool.o readahead.o slab.o swap.o truncate.o vmscan.o \ prio_tree.o $(mmu-y) -obj-$(CONFIG_SWAP) += page_io.o swap_state.o swapfile.o thrash.o +obj-$(CONFIG_SWAP) += page_io.o swap_state.o swapfile.o thrash.o \ + nonresident.o obj-$(CONFIG_HUGETLBFS) += hugetlb.o obj-$(CONFIG_NUMA) += mempolicy.o obj-$(CONFIG_SHMEM) += shmem.o - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
