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futriix/src/quicklist.h
sundb 2168ccc661
Add listpack encoding for list (#11303) 
Improve memory efficiency of list keys

## Description of the feature
The new listpack encoding uses the old `list-max-listpack-size` config
to perform the conversion, which we can think it of as a node inside a
quicklist, but without 80 bytes overhead (internal fragmentation included)
of quicklist and quicklistNode structs.
For example, a list key with 5 items of 10 chars each, now takes 128 bytes
instead of 208 it used to take.

## Conversion rules
* Convert listpack to quicklist
  When the listpack length or size reaches the `list-max-listpack-size` limit,
  it will be converted to a quicklist.
* Convert quicklist to listpack
  When a quicklist has only one node, and its length or size is reduced to half
  of the `list-max-listpack-size` limit, it will be converted to a listpack.
  This is done to avoid frequent conversions when we add or remove at the bounding size or length.
    
## Interface changes
1. add list entry param to listTypeSetIteratorDirection
    When list encoding is listpack, `listTypeIterator->lpi` points to the next entry of current entry,
    so when changing the direction, we need to use the current node (listTypeEntry->p) to 
    update `listTypeIterator->lpi` to the next node in the reverse direction.

## Benchmark
### Listpack VS Quicklist with one node
* LPUSH - roughly 0.3% improvement
* LRANGE - roughly 13% improvement

### Both are quicklist
* LRANGE - roughly 3% improvement
* LRANGE without pipeline - roughly 3% improvement

From the benchmark, as we can see from the results
1. When list is quicklist encoding, LRANGE improves performance by <5%.
2. When list is listpack encoding, LRANGE improves performance by ~13%,
   the main enhancement is brought by `addListListpackRangeReply()`.

## Memory usage
1M lists(key:0~key:1000000) with 5 items of 10 chars ("hellohello") each.
shows memory usage down by 35.49%, from 214MB to 138MB.

## Note
1. Add conversion callback to support doing some work before conversion
    Since the quicklist iterator decompresses the current node when it is released, we can 
    no longer decompress the quicklist after we convert the list.
2022-11-16 20:29:46 +02:00

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/* quicklist.h - A generic doubly linked quicklist implementation
*
* Copyright (c) 2014, Matt Stancliff <matt@genges.com>
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* * Redistributions of source code must retain the above copyright notice,
* this quicklist of conditions and the following disclaimer.
* * Redistributions in binary form must reproduce the above copyright
* notice, this quicklist of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* * Neither the name of Redis nor the names of its contributors may be used
* to endorse or promote products derived from this software without
* specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*/
#include <stdint.h> // for UINTPTR_MAX
#ifndef __QUICKLIST_H__
#define __QUICKLIST_H__
/* Node, quicklist, and Iterator are the only data structures used currently. */
/* quicklistNode is a 32 byte struct describing a listpack for a quicklist.
* We use bit fields keep the quicklistNode at 32 bytes.
* count: 16 bits, max 65536 (max lp bytes is 65k, so max count actually < 32k).
* encoding: 2 bits, RAW=1, LZF=2.
* container: 2 bits, PLAIN=1 (a single item as char array), PACKED=2 (listpack with multiple items).
* recompress: 1 bit, bool, true if node is temporary decompressed for usage.
* attempted_compress: 1 bit, boolean, used for verifying during testing.
* extra: 10 bits, free for future use; pads out the remainder of 32 bits */
typedef struct quicklistNode {
struct quicklistNode *prev;
struct quicklistNode *next;
unsigned char *entry;
size_t sz; /* entry size in bytes */
unsigned int count : 16; /* count of items in listpack */
unsigned int encoding : 2; /* RAW==1 or LZF==2 */
unsigned int container : 2; /* PLAIN==1 or PACKED==2 */
unsigned int recompress : 1; /* was this node previous compressed? */
unsigned int attempted_compress : 1; /* node can't compress; too small */
unsigned int dont_compress : 1; /* prevent compression of entry that will be used later */
unsigned int extra : 9; /* more bits to steal for future usage */
} quicklistNode;
/* quicklistLZF is a 8+N byte struct holding 'sz' followed by 'compressed'.
* 'sz' is byte length of 'compressed' field.
* 'compressed' is LZF data with total (compressed) length 'sz'
* NOTE: uncompressed length is stored in quicklistNode->sz.
* When quicklistNode->entry is compressed, node->entry points to a quicklistLZF */
typedef struct quicklistLZF {
size_t sz; /* LZF size in bytes*/
char compressed[];
} quicklistLZF;
/* Bookmarks are padded with realloc at the end of of the quicklist struct.
* They should only be used for very big lists if thousands of nodes were the
* excess memory usage is negligible, and there's a real need to iterate on them
* in portions.
* When not used, they don't add any memory overhead, but when used and then
* deleted, some overhead remains (to avoid resonance).
* The number of bookmarks used should be kept to minimum since it also adds
* overhead on node deletion (searching for a bookmark to update). */
typedef struct quicklistBookmark {
quicklistNode *node;
char *name;
} quicklistBookmark;
#if UINTPTR_MAX == 0xffffffff
/* 32-bit */
# define QL_FILL_BITS 14
# define QL_COMP_BITS 14
# define QL_BM_BITS 4
#elif UINTPTR_MAX == 0xffffffffffffffff
/* 64-bit */
# define QL_FILL_BITS 16
# define QL_COMP_BITS 16
# define QL_BM_BITS 4 /* we can encode more, but we rather limit the user
since they cause performance degradation. */
#else
# error unknown arch bits count
#endif
/* quicklist is a 40 byte struct (on 64-bit systems) describing a quicklist.
* 'count' is the number of total entries.
* 'len' is the number of quicklist nodes.
* 'compress' is: 0 if compression disabled, otherwise it's the number
* of quicklistNodes to leave uncompressed at ends of quicklist.
* 'fill' is the user-requested (or default) fill factor.
* 'bookmarks are an optional feature that is used by realloc this struct,
* so that they don't consume memory when not used. */
typedef struct quicklist {
quicklistNode *head;
quicklistNode *tail;
unsigned long count; /* total count of all entries in all listpacks */
unsigned long len; /* number of quicklistNodes */
signed int fill : QL_FILL_BITS; /* fill factor for individual nodes */
unsigned int compress : QL_COMP_BITS; /* depth of end nodes not to compress;0=off */
unsigned int bookmark_count: QL_BM_BITS;
quicklistBookmark bookmarks[];
} quicklist;
typedef struct quicklistIter {
quicklist *quicklist;
quicklistNode *current;
unsigned char *zi; /* points to the current element */
long offset; /* offset in current listpack */
int direction;
} quicklistIter;
typedef struct quicklistEntry {
const quicklist *quicklist;
quicklistNode *node;
unsigned char *zi;
unsigned char *value;
long long longval;
size_t sz;
int offset;
} quicklistEntry;
#define QUICKLIST_HEAD 0
#define QUICKLIST_TAIL -1
/* quicklist node encodings */
#define QUICKLIST_NODE_ENCODING_RAW 1
#define QUICKLIST_NODE_ENCODING_LZF 2
/* quicklist compression disable */
#define QUICKLIST_NOCOMPRESS 0
/* quicklist node container formats */
#define QUICKLIST_NODE_CONTAINER_PLAIN 1
#define QUICKLIST_NODE_CONTAINER_PACKED 2
#define QL_NODE_IS_PLAIN(node) ((node)->container == QUICKLIST_NODE_CONTAINER_PLAIN)
#define quicklistNodeIsCompressed(node) \
((node)->encoding == QUICKLIST_NODE_ENCODING_LZF)
/* Prototypes */
quicklist *quicklistCreate(void);
quicklist *quicklistNew(int fill, int compress);
void quicklistSetCompressDepth(quicklist *quicklist, int depth);
void quicklistSetFill(quicklist *quicklist, int fill);
void quicklistSetOptions(quicklist *quicklist, int fill, int depth);
void quicklistRelease(quicklist *quicklist);
int quicklistPushHead(quicklist *quicklist, void *value, const size_t sz);
int quicklistPushTail(quicklist *quicklist, void *value, const size_t sz);
void quicklistPush(quicklist *quicklist, void *value, const size_t sz,
int where);
void quicklistAppendListpack(quicklist *quicklist, unsigned char *zl);
void quicklistAppendPlainNode(quicklist *quicklist, unsigned char *data, size_t sz);
void quicklistInsertAfter(quicklistIter *iter, quicklistEntry *entry,
void *value, const size_t sz);
void quicklistInsertBefore(quicklistIter *iter, quicklistEntry *entry,
void *value, const size_t sz);
void quicklistDelEntry(quicklistIter *iter, quicklistEntry *entry);
void quicklistReplaceEntry(quicklistIter *iter, quicklistEntry *entry,
void *data, size_t sz);
int quicklistReplaceAtIndex(quicklist *quicklist, long index, void *data,
const size_t sz);
int quicklistDelRange(quicklist *quicklist, const long start, const long stop);
quicklistIter *quicklistGetIterator(quicklist *quicklist, int direction);
quicklistIter *quicklistGetIteratorAtIdx(quicklist *quicklist,
int direction, const long long idx);
quicklistIter *quicklistGetIteratorEntryAtIdx(quicklist *quicklist, const long long index,
quicklistEntry *entry);
int quicklistNext(quicklistIter *iter, quicklistEntry *entry);
void quicklistSetDirection(quicklistIter *iter, int direction);
void quicklistReleaseIterator(quicklistIter *iter);
quicklist *quicklistDup(quicklist *orig);
void quicklistRotate(quicklist *quicklist);
int quicklistPopCustom(quicklist *quicklist, int where, unsigned char **data,
size_t *sz, long long *sval,
void *(*saver)(unsigned char *data, size_t sz));
int quicklistPop(quicklist *quicklist, int where, unsigned char **data,
size_t *sz, long long *slong);
unsigned long quicklistCount(const quicklist *ql);
int quicklistCompare(quicklistEntry *entry, unsigned char *p2, const size_t p2_len);
size_t quicklistGetLzf(const quicklistNode *node, void **data);
void quicklistNodeLimit(int fill, size_t *size, unsigned int *count);
int quicklistNodeExceedsLimit(int fill, size_t new_sz, unsigned int new_count);
void quicklistRepr(unsigned char *ql, int full);
/* bookmarks */
int quicklistBookmarkCreate(quicklist **ql_ref, const char *name, quicklistNode *node);
int quicklistBookmarkDelete(quicklist *ql, const char *name);
quicklistNode *quicklistBookmarkFind(quicklist *ql, const char *name);
void quicklistBookmarksClear(quicklist *ql);
int quicklistisSetPackedThreshold(size_t sz);
#ifdef REDIS_TEST
int quicklistTest(int argc, char *argv[], int flags);
#endif
/* Directions for iterators */
#define AL_START_HEAD 0
#define AL_START_TAIL 1
#endif /* __QUICKLIST_H__ */
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