1Cache::FastMmap(3) User Contributed Perl Documentation Cache::FastMmap(3)
2
6 Cache::FastMmap - Uses an mmap'ed file to act as a shared memory
7 interprocess cache
8
10 use Cache::FastMmap;
11 # Uses vaguely sane defaults
13 $Cache = Cache::FastMmap->new();
14 # Uses Storable to serialize $Value to bytes for storage
16 $Cache->set($Key, $Value);
17 $Value = $Cache->get($Key);
18 $Cache = Cache::FastMmap->new(serializer => '');
20 # Stores stringified bytes of $Value directly
22 $Cache->set($Key, $Value);
23 $Value = $Cache->get($Key);
24
26 A shared memory cache through an mmap'ed file. It's core is written in
27 C for performance. It uses fcntl locking to ensure multiple processes
28 can safely access the cache at the same time. It uses a basic LRU
29 algorithm to keep the most used entries in the cache.
30
32 In multi-process environments (eg mod_perl, forking daemons, etc), it's
33 common to want to cache information, but have that cache shared between
34 processes. Many solutions already exist, and may suit your situation
35 better:
36 • MLDBM::Sync - acts as a database, data is not automatically
38 expired, slow
39 • IPC::MM - hash implementation is broken, data is not automatically
41 expired, slow
42 • Cache::FileCache - lots of features, slow
44 • Cache::SharedMemoryCache - lots of features, VERY slow. Uses
46 IPC::ShareLite which freeze/thaws ALL data at each read/write
47 • DBI - use your favourite RDBMS. can perform well, need a DB server
49 running. very global. socket connection latency
50 • Cache::Mmap - similar to this module, in pure perl. slows down with
52 larger pages
53 • BerkeleyDB - very fast (data ends up mostly in shared memory cache)
55 but acts as a database overall, so data is not automatically
56 expired
57 In the case I was working on, I needed:
59 • Automatic expiry and space management
61 • Very fast access to lots of small items
63 • The ability to fetch/store many items in one go
65 Which is why I developed this module. It tries to be quite efficient
67 through a number of means:
68 • Core code is written in C for performance
70 • It uses multiple pages within a file, and uses Fcntl to only lock a
72 page at a time to reduce contention when multiple processes access
73 the cache.
74 • It uses a dual level hashing system (hash to find page, then hash
76 within each page to find a slot) to make most get() calls O(1) and
77 fast
78 • On each set(), if there are slots and page space available, only
80 the slot has to be updated and the data written at the end of the
81 used data space. If either runs out, a re-organisation of the page
82 is performed to create new slots/space which is done in an
83 efficient way
84 The class also supports read-through, and write-back or write-through
86 callbacks to access the real data if it's not in the cache, meaning
87 that code like this:
88 my $Value = $Cache->get($Key);
90 if (!defined $Value) {
91 $Value = $RealDataSource->get($Key);
92 $Cache->set($Key, $Value)
93 }
94 Isn't required, you instead specify in the constructor:
96 Cache::FastMmap->new(
98 ...
99 context => $RealDataSourceHandle,
100 read_cb => sub { $_[0]->get($_[1]) },
101 write_cb => sub { $_[0]->set($_[1], $_[2]) },
102 );
103 And then:
105 my $Value = $Cache->get($Key);
107 $Cache->set($Key, $NewValue);
109 Will just work and will be read/written to the underlying data source
111 as needed automatically.
112
114 If you're storing relatively large and complex structures into the
115 cache, then you're limited by the speed of the Storable module. If
116 you're storing simple structures, or raw data, then Cache::FastMmap has
117 noticeable performance improvements.
118 See <http://cpan.robm.fastmail.fm/cache_perf.html> for some comparisons
120 to other modules.
121
123 Cache::FastMmap uses mmap to map a file as the shared cache space, and
124 fcntl to do page locking. This means it should work on most UNIX like
125 operating systems.
126 Ash Berlin has written a Win32 layer using MapViewOfFile et al. to
128 provide support for Win32 platform.
129
131 Because Cache::FastMmap mmap's a shared file into your processes memory
132 space, this can make each process look quite large, even though it's
133 just mmap'd memory that's shared between all processes that use the
134 cache, and may even be swapped out if the cache is getting low usage.
135 However, the OS will think your process is quite large, which might
137 mean you hit some BSD::Resource or 'ulimits' you set previously that
138 you thought were sane, but aren't anymore, so be aware.
139
141 Because Cache::FastMmap uses an mmap'ed file, when you put values into
142 the cache, you are actually "dirtying" pages in memory that belong to
143 the cache file. Your OS will want to write those dirty pages back to
144 the file on the actual physical disk, but the rate it does that at is
145 very OS dependent.
146 In Linux, you have some control over how the OS writes those pages back
148 using a number of parameters in /proc/sys/vm
149 dirty_background_ratio
151 dirty_expire_centisecs
152 dirty_ratio
153 dirty_writeback_centisecs
154 How you tune these depends heavily on your setup.
156 As an interesting point, if you use a highmem linux kernel, a change
158 between 2.6.16 and 2.6.20 made the kernel flush memory a LOT more.
159 There's details in this kernel mailing list thread:
160 <http://www.uwsg.iu.edu/hypermail/linux/kernel/0711.3/0804.html>
161 In most cases, people are not actually concerned about the persistence
163 of data in the cache, and so are happy to disable writing of any cache
164 data back to disk at all. Baically what they want is an in memory only
165 shared cache. The best way to do that is to use a "tmpfs" filesystem
166 and put all cache files on there.
167 For instance, all our machines have a /tmpfs mount point that we create
169 in /etc/fstab as:
170 none /tmpfs tmpfs defaults,noatime,size=1000M 0 0
172 And we put all our cache files on there. The tmpfs filesystem is smart
174 enough to only use memory as required by files actually on the tmpfs,
175 so making it 1G in size doesn't actually use 1G of memory, it only uses
176 as much as the cache files we put on it. In all cases, we ensure that
177 we never run out of real memory, so the cache files effectively act
178 just as named access points to shared memory.
179 Some people have suggested using anonymous mmaped memory. Unfortunately
181 we need a file descriptor to do the fcntl locking on, so we'd have to
182 create a separate file on a filesystem somewhere anyway. It seems
183 easier to just create an explicit "tmpfs" filesystem.
184
186 To reduce lock contention, Cache::FastMmap breaks up the file into
187 pages. When you get/set a value, it hashes the key to get a page, then
188 locks that page, and uses a hash table within the page to get/store the
189 actual key/value pair.
190 One consequence of this is that you cannot store values larger than a
192 page in the cache at all. Attempting to store values larger than a page
193 size will fail (the set() function will return false).
194 Also keep in mind that each page has it's own hash table, and that we
196 store the key and value data of each item. So if you are expecting to
197 store large values and/or keys in the cache, you should use page sizes
198 that are definitely larger than your largest key + value size + a few
199 kbytes for the overhead.
200
202 Because the cache uses shared memory through an mmap'd file, you have
203 to make sure each process connects up to the file. There's probably two
204 main ways to do this:
205 • Create the cache in the parent process, and then when it forks,
207 each child will inherit the same file descriptor, mmap'ed memory,
208 etc and just work. This is the recommended way. (BEWARE: This only
209 works under UNIX as Win32 has no concept of forking)
210 • Explicitly connect up in each forked child to the share file. In
212 this case, make sure the file already exists and the children
213 connect with init_file => 0 to avoid deleting the cache contents
214 and possible race corruption conditions. Also be careful that
215 multiple children may race to create the file at the same time,
216 each overwriting and corrupting content. Use a separate lock file
217 if you must to ensure only one child creates the file. (This is the
218 only possible way under Win32)
219 The first way is usually the easiest. If you're using the cache in a
221 Net::Server based module, you'll want to open the cache in the
222 "pre_loop_hook", because that's executed before the fork, but after the
223 process ownership has changed and any chroot has been done.
224 In mod_perl, just open the cache at the global level in the appropriate
226 module, which is executed as the server is starting and before it
227 starts forking children, but you'll probably want to chmod or chown the
228 file to the permissions of the apache process.
229
231 Cache::FastMmap is being used in an extensive number of systems at
232 www.fastmail.com and is regarded as extremely stable and reliable.
233 Development has in general slowed because there are currently no known
234 bugs and no additional needed features at this time.
235
237 new(%Opts)
238 Create a new Cache::FastMmap object.
239 Basic global parameters are:
241 • share_file
243 File to mmap for sharing of data. default on unix:
245 /tmp/sharefile-$pid-$time-$random default on windows:
246 %TEMP%\sharefile-$pid-$time-$random
247 • init_file
249 Clear any existing values and re-initialise file. Useful to do
251 in a parent that forks off children to ensure that file is
252 empty at the start (default: 0)
253 Note: This is quite important to do in the parent to ensure a
255 consistent file structure. The shared file is not perfectly
256 transaction safe, and so if a child is killed at the wrong
257 instant, it might leave the cache file in an inconsistent
258 state.
259 • serializer
261 Use a serialization library to serialize perl data structures
263 before storing in the cache. If not set, the raw value in the
264 variable passed to set() is stored as a string. You must set
265 this if you want to store anything other than basic scalar
266 values. Supported values are:
267 '' for none
269 'storable' for 'Storable'
270 'sereal' for 'Sereal'
271 'json' for 'JSON'
272 [ $s, $d ] for custom serializer/de-serializer
273 If this parameter has a value the module will attempt to load
275 the associated package and then use the API of that package to
276 serialize data before storing in the cache, and deserialize it
277 upon retrieval from the cache. (default: 'storable')
278 You can use a custom serializer/de-serializer by passing an
280 array-ref with two values. The first should be a subroutine
281 reference that takes the data to serialize as a single argument
282 and returns an octet stream to store. The second should be a
283 subroutine reference that takes the octet stream as a single
284 argument and returns the original data structure.
285 One thing to note, the data structure passed to the serializer
287 is always a *scalar* reference to the original data passed in
288 to the ->set(...) call. If your serializer doesn't support
289 that, you might need to dereference it first before storing,
290 but rembember to return a reference again in the de-serializer.
291 (Note: Historically this module only supported a boolean value
293 for the `raw_values` parameter and defaulted to 0, which meant
294 it used Storable to serialze all values.)
295 • raw_values
297 Deprecated. Use serializer above
299 • compressor
301 Compress the value (but not the key) before storing into the
303 cache, using the compression package identified by the value of
304 the parameter. Supported values are:
305 'zlib' for 'Compress::Zlib'
307 'lz4' for 'Compress::LZ4'
308 'snappy' for 'Compress::Snappy'
309 [ $c, $d ] for custom compressor/de-compressor
310 If this parameter has a value the module will attempt to load
312 the associated package and then use the API of that package to
313 compress data before storing in the cache, and uncompress it
314 upon retrieval from the cache. (default: undef)
315 You can use a custom compressor/de-compressor by passing an
317 array-ref with two values. The first should be a subroutine
318 reference that takes the data to compress as a single octet
319 stream argument and returns an octet stream to store. The
320 second should be a subroutine reference that takes the
321 compressed octet stream as a single argument and returns the
322 original uncompressed data.
323 (Note: Historically this module only supported a boolean value
325 for the `compress` parameter and defaulted to use
326 Compress::Zlib. The note for the old `compress` parameter
327 stated: "Some initial testing shows that the uncompressing
328 tends to be very fast, though the compressing can be quite
329 slow, so it's probably best to use this option only if you know
330 values in the cache are long-lived and have a high hit rate."
331 Comparable test results for the other compression tools are not
333 yet available; submission of benchmarks welcome. However, the
334 documentation for the 'Snappy' library
335 (http://google.github.io/snappy/) states: For instance,
336 compared to the fastest mode of zlib, Snappy is an order of
337 magnitude faster for most inputs, but the resulting compressed
338 files are anywhere from 20% to 100% bigger. )
339 • compress
341 Deprecated. Please use compressor, see above.
343 • enable_stats
345 Enable some basic statistics capturing. When enabled, every
347 read to the cache is counted, and every read to the cache that
348 finds a value in the cache is also counted. You can then
349 retrieve these values via the get_statistics() call. This
350 causes every read action to do a write on a page, which can
351 cause some more IO, so it's disabled by default. (default: 0)
352 • expire_time
354 Maximum time to hold values in the cache in seconds. A value of
356 0 means does no explicit expiry time, and values are expired
357 only based on LRU usage. Can be expressed as 1m, 1h, 1d for
358 minutes/hours/days respectively. (default: 0)
359 You may specify the cache size as:
361 • cache_size
363 Size of cache. Can be expresses as 1k, 1m for kilobytes or
365 megabytes respectively. Automatically guesses page size/page
366 count values.
367 Or specify explicit page size/page count values. If none of these
369 are specified, the values page_size = 64k and num_pages = 89 are
370 used.
371 • page_size
373 Size of each page. Must be a power of 2 between 4k and 1024k.
375 If not, is rounded to the nearest value.
376 • num_pages
378 Number of pages. Should be a prime number for best hashing
380 The cache allows the use of callbacks for reading/writing data to
382 an underlying data store.
383 • context
385 Opaque reference passed as the first parameter to any callback
387 function if specified
388 • read_cb
390 Callback to read data from the underlying data store. Called
392 as:
393 $read_cb->($context, $Key)
395 Should return the value to use. This value will be saved in the
397 cache for future retrievals. Return undef if there is no value
398 for the given key
399 • write_cb
401 Callback to write data to the underlying data store. Called
403 as:
404 $write_cb->($context, $Key, $Value, $ExpiryTime)
406 In 'write_through' mode, it's always called as soon as a
408 set(...) is called on the Cache::FastMmap class. In
409 'write_back' mode, it's called when a value is expunged from
410 the cache if it's been changed by a set(...) rather than read
411 from the underlying store with the read_cb above.
412 Note: Expired items do result in the write_cb being called if
414 'write_back' caching is enabled and the item has been changed.
415 You can check the $ExpiryTime against time() if you only want
416 to write back values which aren't expired.
417 Also remember that write_cb may be called in a different
419 process to the one that placed the data in the cache in the
420 first place
421 • delete_cb
423 Callback to delete data from the underlying data store. Called
425 as:
426 $delete_cb->($context, $Key)
428 Called as soon as remove(...) is called on the Cache::FastMmap
430 class
431 • cache_not_found
433 If set to true, then if the read_cb is called and it returns
435 undef to say nothing was found, then that information is stored
436 in the cache, so that next time a get(...) is called on that
437 key, undef is returned immediately rather than again calling
438 the read_cb
439 • write_action
441 Either 'write_back' or 'write_through'. (default:
443 write_through)
444 • allow_recursive
446 If you're using a callback function, then normally the cache is
448 not re-enterable, and attempting to call a get/set on the cache
449 will cause an error. By setting this to one, the cache will
450 unlock any pages before calling the callback. During the unlock
451 time, other processes may change data in current cache page,
452 causing possible unexpected effects. You shouldn't set this
453 unless you know you want to be able to recall to the cache
454 within a callback. (default: 0)
455 • empty_on_exit
457 When you have 'write_back' mode enabled, then you really want
459 to make sure all values from the cache are expunged when your
460 program exits so any changes are written back.
461 The trick is that we only want to do this in the parent
463 process, we don't want any child processes to empty the cache
464 when they exit. So if you set this, it takes the PID via $$,
465 and only calls empty in the DESTROY method if $$ matches the
466 pid we captured at the start. (default: 0)
467 • unlink_on_exit
469 Unlink the share file when the cache is destroyed.
471 As with empty_on_exit, this will only unlink the file if the
473 DESTROY occurs in the same PID that the cache was created in so
474 that any forked children don't unlink the file.
475 This value defaults to 1 if the share_file specified does not
477 already exist. If the share_file specified does already exist,
478 it defaults to 0.
479 • catch_deadlocks
481 Sets an alarm(10) before each page is locked via
483 fcntl(F_SETLKW) to catch any deadlock. This used to be the
484 default behaviour, but it's not really needed in the default
485 case and could clobber sub-second Time::HiRes alarms setup by
486 other code. Defaults to 0.
487 get($Key, [ \%Options ])
489 Search cache for given Key. Returns undef if not found. If read_cb
490 specified and not found, calls the callback to try and find the
491 value for the key, and if found (or 'cache_not_found' is set),
492 stores it into the cache and returns the found value.
493 %Options is optional, and is used by get_and_set() to control the
495 locking behaviour. For now, you should probably ignore it unless
496 you read the code to understand how it works
497 set($Key, $Value, [ \%Options ])
499 Store specified key/value pair into cache
500 %Options is optional. If it's not a hash reference, it's assumed to
502 be an explicit expiry time for the key being set, this is to make
503 set() compatible with the Cache::Cache interface
504 If a hash is passed, the only useful entries right now are
506 expire_on to set an explicit expiry time for this entry (epoch
507 seconds), or expire_time to set an explicit relative future expiry
508 time for this entry in seconds/minutes/days in the same format as
509 passed to the new constructor.
510 Some other options are used internally, such as by get_and_set() to
512 control the locking behaviour. For now, you should probably ignore
513 it unless you read the code to understand how it works
514 This method returns true if the value was stored in the cache,
516 false otherwise. See the PAGE SIZE AND KEY/VALUE LIMITS section for
517 more details.
518 get_and_set($Key, $AtomicSub)
520 Atomically retrieve and set the value of a Key.
521 The page is locked while retrieving the $Key and is unlocked only
523 after the value is set, thus guaranteeing the value does not change
524 between the get and set operations.
525 $AtomicSub is a reference to a subroutine that is called to
527 calculate the new value to store. $AtomicSub gets $Key, the current
528 value from the cache, and an options hash as paramaters. Currently
529 the only option passed is the expire_on of the item.
530 It should return the new value to set in the cache for the given
532 $Key, and an optional hash of arguments in the same format as would
533 be passed to a set() call.
534 If $AtomicSub returns an empty list, no value is stored back in the
536 cache. This avoids updating the expiry time on an entry if you want
537 to do a "get if in cache, store if not present" type callback.
538 For example:
540 • To atomically increment a value in the cache
542 $Cache->get_and_set($Key, sub { return $_[1]+1; });
544 • To add an item to a cached list and set the expiry time
546 depending on the size of the list
547 $Cache->get_and_set($Key, sub ($, $v) {
549 push @$v, $item;
550 return ($v, { expire_time => @$v > 2 ? '10s' : '2m' });
551 });
552 • To update a counter, but maintain the original expiry time
554 $Cache->get_and_set($Key, sub {
556 return ($_[1]+1, { expire_on => $_[2]->{expire_on} );
557 });
558 In scalar context the return value from get_and_set(), is the *new*
560 value stored back into the cache.
561 In list context, a two item array is returned; the new value stored
563 back into the cache and a boolean that's true if the value was
564 stored in the cache, false otherwise. See the PAGE SIZE AND
565 KEY/VALUE LIMITS section for more details.
566 Notes:
568 • Do not perform any get/set operations from the callback sub, as
570 these operations lock the page and you may end up with a dead
571 lock!
572 • If your sub does a die/throws an exception, the page will
574 correctly be unlocked (1.15 onwards)
575 remove($Key, [ \%Options ])
577 Delete the given key from the cache
578 %Options is optional, and is used by get_and_remove() to control
580 the locking behaviour. For now, you should probably ignore it
581 unless you read the code to understand how it works
582 get_and_remove($Key)
584 Atomically retrieve value of a Key while removing it from the
585 cache.
586 The page is locked while retrieving the $Key and is unlocked only
588 after the value is removed, thus guaranteeing the value stored by
589 someone else isn't removed by us.
590 expire($Key)
592 Explicitly expire the given $Key. For a cache in write-back mode,
593 this will cause the item to be written back to the underlying store
594 if dirty, otherwise it's the same as removing the item.
595 clear()
597 Clear all items from the cache
598 Note: If you're using callbacks, this has no effect on items in the
600 underlying data store. No delete callbacks are made
601 purge()
603 Clear all expired items from the cache
604 Note: If you're using callbacks, this has no effect on items in the
606 underlying data store. No delete callbacks are made, and no write
607 callbacks are made for the expired data
608 empty($OnlyExpired)
610 Empty all items from the cache, or if $OnlyExpired is true, only
611 expired items.
612 Note: If 'write_back' mode is enabled, any changed items are
614 written back to the underlying store. Expired items are written
615 back to the underlying store as well.
616 get_keys($Mode)
618 Get a list of keys/values held in the cache. May immediately be out
619 of date because of the shared access nature of the cache
620 If $Mode == 0, an array of keys is returned
622 If $Mode == 1, then an array of hashrefs, with 'key',
624 'last_access', 'expire_on' and 'flags' keys is returned
625 If $Mode == 2, then hashrefs also contain 'value' key
627 get_statistics($Clear)
629 Returns a two value list of (nreads, nreadhits). This only works if
630 you passed enable_stats in the constructor
631 nreads is the total number of read attempts done on the cache since
633 it was created
634 nreadhits is the total number of read attempts done on the cache
636 since it was created that found the key/value in the cache
637 If $Clear is true, the values are reset immediately after they are
639 retrieved
640 multi_get($PageKey, [ $Key1, $Key2, ... ])
642 The two multi_xxx routines act a bit differently to the other
643 routines. With the multi_get, you pass a separate PageKey value and
644 then multiple keys. The PageKey value is hashed, and that page
645 locked. Then that page is searched for each key. It returns a hash
646 ref of Key => Value items found in that page in the cache.
647 The main advantage of this is just a speed one, if you happen to
649 need to search for a lot of items on each call.
650 For instance, say you have users and a bunch of pieces of separate
652 information for each user. On a particular run, you need to
653 retrieve a sub-set of that information for a user. You could do
654 lots of get() calls, or you could use the 'username' as the page
655 key, and just use one multi_get() and multi_set() call instead.
656 A couple of things to note:
658 1. This makes multi_get()/multi_set() and get()/set()
660 incompatible. Don't mix calls to the two, because you won't
661 find the data you're expecting
662 2. The writeback and callback modes of operation do not work with
664 multi_get()/multi_set(). Don't attempt to use them together.
665 multi_set($PageKey, { $Key1 = $Value1, $Key2 => $Value2, ... }, [
667 \%Options ])>
668 Store specified key/value pair into cache
669
671 _expunge_all($Mode, $WB)
672 Expunge all items from the cache
673 Expunged items (that have not expired) are written back to the
675 underlying store if write_back is enabled
676 _expunge_page($Mode, $WB, $Len)
678 Expunge items from the current page to make space for $Len bytes
679 key/value items
680 Expunged items (that have not expired) are written back to the
682 underlying store if write_back is enabled
683 _lock_page($Page)
685 Lock a given page in the cache, and return an object reference that
686 when DESTROYed, unlocks the page
687
689 • From 1.15
690 • Default share_file name is no-longer /tmp/sharefile, but
692 /tmp/sharefile-$pid-$time. This ensures that different
693 runs/processes don't interfere with each other, but means you
694 may not connect up to the file you expect. You should be
695 choosing an explicit name in most cases.
696 On Unix systems, you can pass in the environment variable
698 TMPDIR to override the default directory of /tmp
699 • The new option unlink_on_exit defaults to true if you pass a
701 filename for the share_file which doesn't already exist. This
702 means if you have one process that creates the file, and
703 another that expects the file to be there, by default it won't
704 be.
705 Otherwise the defaults seem sensible to cleanup unneeded share
707 files rather than leaving them around to accumulate.
708 • From 1.29
710 • Default share_file name is no longer /tmp/sharefile-$pid-$time
712 but /tmp/sharefile-$pid-$time-$random.
713 • From 1.31
715 • Before 1.31, if you were using raw_values => 0 mode, then the
717 write_cb would be called with raw frozen data, rather than the
718 thawed object. From 1.31 onwards, it correctly calls write_cb
719 with the thawed object value (eg what was passed to the ->set()
720 call in the first place)
721 • From 1.36
723 • Before 1.36, an alarm(10) would be set before each attempt to
725 lock a page. The only purpose of this was to detect deadlocks,
726 which should only happen if the Cache::FastMmap code was buggy,
727 or a callback function in get_and_set() made another call into
728 Cache::FastMmap.
729 However this added unnecessary extra system calls for every
731 lookup, and for users using Time::HiRes, it could clobber any
732 existing alarms that had been set with sub-second resolution.
733 So this has now been made an optional feature via the
735 catch_deadlocks option passed to new.
736 • From 1.52
738 • The term expire_time was overloaded in the code to sometimes
740 mean a relative future time (e.g. as passed to new constructor)
741 or an absolute unix epoch (e.g. as returned from get_keys(2)).
742 To avoid this confusion, the code now uses expire_time to
744 always means a relative future time, and expire_on to mean an
745 absolute epoch time. You can use either as an optional argument
746 to a set() call.
747 Since expire_time was used in the constructor and is likely
749 more commonly used, I changed the result of get_keys(2) so it
750 now returns expire_on rather than expire_time.
751
753 MLDBM::Sync, IPC::MM, Cache::FileCache, Cache::SharedMemoryCache, DBI,
754 Cache::Mmap, BerkeleyDB
755 Latest news/details can also be found at:
757 <http://cpan.robm.fastmail.fm/cachefastmmap/>
759 Available on github at:
761 <https://github.com/robmueller/cache-fastmmap/>
763
765 Rob Mueller <mailto:cpan@robm.fastmail.fm>
766
768 Copyright (C) 2003-2017 by FastMail Pty Ltd
769 This library is free software; you can redistribute it and/or modify it
771 under the same terms as Perl itself.
772perl v5.36.0 2023-01-20 Cache::FastMmap(3)