Messages in this thread Patch in this message | | | From | Peter Zijlstra <> | Subject | [PATCH 26/34] mm: clockpro-nonresident.patch | Date | Wed, 22 Mar 2006 23:36:03 +0100 |
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From: Rik van Riel <riel@redhat.com>
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 <riel@redhat.com> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Signed-off-by: Marcelo Tosatti <marcelo.tosatti@cyclades.com>
---
include/linux/nonresident.h | 12 +++ mm/nonresident.c | 167 ++++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 179 insertions(+)
Index: linux-2.6/mm/nonresident.c =================================================================== --- /dev/null 1970-01-01 00:00:00.000000000 +0000 +++ linux-2.6/mm/nonresident.c 2006-03-13 20:45:26.000000000 +0100 @@ -0,0 +1,167 @@ +/* + * mm/nonresident.c + * (C) 2004,2005 Red Hat, Inc + * Written by Rik van Riel <riel@redhat.com> + * 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 <linux/mm.h> +#include <linux/cache.h> +#include <linux/spinlock.h> +#include <linux/bootmem.h> +#include <linux/hash.h> +#include <linux/prefetch.h> +#include <linux/kernel.h> + +/* 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(u32)) + +struct nr_bucket +{ + atomic_t hand; + u32 page[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 = 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 * nr_bucket; + int distance; + u32 wanted; + int i; + + prefetch(mapping->host); + nr_bucket = nr_hash(mapping, index); + + prefetch(nr_bucket); + wanted = nr_cookie(mapping, index); + + for (i = 0; i < NUM_NR; i++) { + if (nr_bucket->page[i] == wanted) { + nr_bucket->page[i] = 0; + /* Return the distance between entry and clock hand. */ + distance = atomic_read(&nr_bucket->hand) + NUM_NR - i; + distance %= NUM_NR; + return (distance << nonres_shift) + (nr_bucket - nonres_table); + } + } + + return ~0UL; +} + +u32 nonresident_put(struct address_space * mapping, unsigned long index) +{ + struct nr_bucket * nr_bucket; + u32 nrpage; + int i; + + prefetch(mapping->host); + nr_bucket = nr_hash(mapping, index); + + prefetchw(nr_bucket); + nrpage = nr_cookie(mapping, index); + + /* Atomically find the next array index. */ + preempt_disable(); +retry: + i = atomic_inc_return(&nr_bucket->hand); + if (unlikely(i >= NUM_NR)) { + if (i == NUM_NR) + atomic_set(&nr_bucket->hand, -1); + goto retry; + } + preempt_enable(); + + /* Statistics may want to know whether the entry was in use. */ + return xchg(&nr_bucket->page[i], nrpage); +} + +unsigned long fastcall 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 = 1; +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; + target /= (sizeof(struct nr_bucket) / sizeof(u32)); + + nonres_table = alloc_large_system_hash("Non-resident page tracking", + sizeof(struct nr_bucket), + target, + 0, + HASH_EARLY | HASH_HIGHMEM, + &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 1970-01-01 00:00:00.000000000 +0000 +++ linux-2.6/include/linux/nonresident.h 2006-03-13 20:45:26.000000000 +0100 @@ -0,0 +1,12 @@ +#ifndef _LINUX_NONRESIDENT_H_ +#define _LINUX_NONRESIDENT_H_ + +#ifdef __KERNEL__ + +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 fastcall nonresident_total(void); + +#endif /* __KERNEL */ +#endif /* _LINUX_NONRESIDENT_H_ */ - 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/
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