]>
git.ipfire.org Git - thirdparty/squid.git/blob - src/repl/heap/store_heap_replacement.cc
5 * DEBUG: section 20 Storage Manager Heap-based replacement
8 * SQUID Web Proxy Cache http://www.squid-cache.org/
9 * ----------------------------------------------------------
11 * Squid is the result of efforts by numerous individuals from
12 * the Internet community; see the CONTRIBUTORS file for full
13 * details. Many organizations have provided support for Squid's
14 * development; see the SPONSORS file for full details. Squid is
15 * Copyrighted (C) 2001 by the Regents of the University of
16 * California; see the COPYRIGHT file for full details. Squid
17 * incorporates software developed and/or copyrighted by other
18 * sources; see the CREDITS file for full details.
20 * This program is free software; you can redistribute it and/or modify
21 * it under the terms of the GNU General Public License as published by
22 * the Free Software Foundation; either version 2 of the License, or
23 * (at your option) any later version.
25 * This program is distributed in the hope that it will be useful,
26 * but WITHOUT ANY WARRANTY; without even the implied warranty of
27 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
28 * GNU General Public License for more details.
30 * You should have received a copy of the GNU General Public License
31 * along with this program; if not, write to the Free Software
32 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111, USA.
37 * The code in this file is Copyrighted (C) 1999 by Hewlett Packard.
40 * For a description of these cache replacement policies see --
41 * http://www.hpl.hp.com/techreports/1999/HPL-1999-69.html
46 #include "store_heap_replacement.h"
48 #include "MemObject.h"
49 #include "SquidTime.h"
56 * Key generation function to implement the LFU-DA policy (Least
57 * Frequently Used with Dynamic Aging). Similar to classical LFU
58 * but with aging to handle turnover of the popular document set.
59 * Maximizes byte hit rate by keeping more currently popular objects
60 * in cache regardless of size. Achieves lower hit rate than GDS
61 * because there are more large objects in cache (so less room for
62 * smaller popular objects).
64 * This version implements a tie-breaker based upon recency
65 * (e->lastref): for objects that have the same reference count
66 * the most recent object wins (gets a higher key value).
68 * Note: this does not properly handle when the aging factor
69 * gets so huge that the added value is outside of the
70 * precision of double. However, Squid has to stay up
71 * for quite a extended period of time (number of requests)
72 * for this to become a problem. (estimation is 10^8 cache
76 HeapKeyGen_StoreEntry_LFUDA(void *entry
, double heap_age
)
78 StoreEntry
*e
= (StoreEntry
*)entry
;
84 else if (squid_curtime
<= e
->lastref
)
87 tie
= 1.0 - exp((double) (e
->lastref
- squid_curtime
) / 86400.0);
89 key
= heap_age
+ (double) e
->refcount
- tie
;
91 debugs(81, 3, "HeapKeyGen_StoreEntry_LFUDA: " << e
->getMD5Text() <<
92 " refcnt=" << e
->refcount
<< " lastref=" << e
->lastref
<<
93 " heap_age=" << heap_age
<< " tie=" << tie
<< " -> " << key
);
95 if (e
->mem_obj
&& e
->mem_obj
->url
)
96 debugs(81, 3, "HeapKeyGen_StoreEntry_LFUDA: url=" << e
->mem_obj
->url
);
102 * Key generation function to implement the GDS-Frequency policy.
103 * Similar to Greedy Dual-Size Hits policy, but adds aging of
104 * documents to prevent pollution. Maximizes object hit rate by
105 * keeping more small, popular objects in cache. Achieves lower
106 * byte hit rate than LFUDA because there are fewer large objects
109 * This version implements a tie-breaker based upon recency
110 * (e->lastref): for objects that have the same reference count
111 * the most recent object wins (gets a higher key value).
113 * Note: this does not properly handle when the aging factor
114 * gets so huge that the added value is outside of the
115 * precision of double. However, Squid has to stay up
116 * for quite a extended period of time (number of requests)
117 * for this to become a problem. (estimation is 10^8 cache
121 HeapKeyGen_StoreEntry_GDSF(void *entry
, double heap_age
)
123 StoreEntry
*e
= (StoreEntry
*)entry
;
125 double size
= e
->swap_file_sz
? (double) e
->swap_file_sz
: 1.0;
126 double tie
= (e
->lastref
> 1) ? (1.0 / e
->lastref
) : 1.0;
127 key
= heap_age
+ ((double) e
->refcount
/ size
) - tie
;
128 debugs(81, 3, "HeapKeyGen_StoreEntry_GDSF: " << e
->getMD5Text() <<
129 " size=" << size
<< " refcnt=" << e
->refcount
<< " lastref=" <<
130 e
->lastref
<< " heap_age=" << heap_age
<< " tie=" << tie
<<
133 if (e
->mem_obj
&& e
->mem_obj
->url
)
134 debugs(81, 3, "HeapKeyGen_StoreEntry_GDSF: url=" << e
->mem_obj
->url
);
140 * Key generation function to implement the LRU policy. Normally
141 * one would not do this with a heap -- use the linked list instead.
142 * For testing and performance characterization it was useful.
143 * Don't use it unless you are trying to compare performance among
144 * heap-based replacement policies...
147 HeapKeyGen_StoreEntry_LRU(void *entry
, double heap_age
)
149 StoreEntry
*e
= (StoreEntry
*)entry
;
150 debugs(81, 3, "HeapKeyGen_StoreEntry_LRU: " <<
151 e
->getMD5Text() << " heap_age=" << heap_age
<<
152 " lastref=" << (double) e
->lastref
);
154 if (e
->mem_obj
&& e
->mem_obj
->url
)
155 debugs(81, 3, "HeapKeyGen_StoreEntry_LRU: url=" << e
->mem_obj
->url
);
157 return (heap_key
) e
->lastref
;