MemStore.h
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1/*
2 * Copyright (C) 1996-2022 The Squid Software Foundation and contributors
3 *
4 * Squid software is distributed under GPLv2+ license and includes
5 * contributions from numerous individuals and organizations.
6 * Please see the COPYING and CONTRIBUTORS files for details.
7 */
8
9#ifndef SQUID_MEMSTORE_H
10#define SQUID_MEMSTORE_H
11
12#include "ipc/mem/Page.h"
13#include "ipc/mem/PageStack.h"
14#include "ipc/StoreMap.h"
15#include "Store.h"
16#include "store/Controlled.h"
17
18// StoreEntry restoration info not already stored by Ipc::StoreMap
21};
24
25class ShmWriter;
26
30{
31public:
32 MemStore();
33 virtual ~MemStore();
34
36 bool keepInLocalMemory(const StoreEntry &e) const;
37
39 void write(StoreEntry &e);
40
43
45 void disconnect(StoreEntry &e);
46
47 /* Storage API */
48 virtual void create() override {}
49 virtual void init() override;
50 virtual StoreEntry *get(const cache_key *) override;
51 virtual uint64_t maxSize() const override;
52 virtual uint64_t minSize() const override;
53 virtual uint64_t currentSize() const override;
54 virtual uint64_t currentCount() const override;
55 virtual int64_t maxObjectSize() const override;
56 virtual void getStats(StoreInfoStats &stats) const override;
57 virtual void stat(StoreEntry &e) const override;
58 virtual void reference(StoreEntry &e) override;
59 virtual bool dereference(StoreEntry &e) override;
60 virtual void updateHeaders(StoreEntry *e) override;
61 virtual void maintain() override;
62 virtual bool anchorToCache(StoreEntry &e, bool &inSync) override;
63 virtual bool updateAnchored(StoreEntry &) override;
64 virtual void evictCached(StoreEntry &) override;
65 virtual void evictIfFound(const cache_key *) override;
66
68 static bool Enabled() { return EntryLimit() > 0; }
69 static int64_t EntryLimit();
72 static bool Requested();
73
74protected:
75 friend ShmWriter;
76
77 bool shouldCache(StoreEntry &e) const;
78 bool startCaching(StoreEntry &e);
79
80 void copyToShm(StoreEntry &e);
82 bool copyFromShm(StoreEntry &e, const sfileno index, const Ipc::StoreMapAnchor &anchor);
83 bool copyFromShmSlice(StoreEntry &e, const StoreIOBuffer &buf, bool eof);
84
86
87 void anchorEntry(StoreEntry &e, const sfileno index, const Ipc::StoreMapAnchor &anchor);
89
91 Ipc::StoreMap::Slice &nextAppendableSlice(const sfileno entryIndex, sfileno &sliceOffset);
93
94 // Ipc::StoreMapCleaner API
95 virtual void noteFreeMapSlice(const Ipc::StoreMapSliceId sliceId) override;
96
97private:
98 // TODO: move freeSlots into map
101
104
107
110 {
111 public:
112 SlotAndPage(): slot(nullptr), page(nullptr) {}
113 bool operator !() const { return !slot && !page; }
116 };
118};
119
120// Why use Store as a base? MemStore and SwapDir are both "caches".
121
122// Why not just use a SwapDir API? That would not help much because Store has
123// to check/update memory cache separately from the disk cache. And same API
124// would hurt because we can support synchronous get/put, unlike the disks.
125
126#endif /* SQUID_MEMSTORE_H */
127
Ipc::StoreMapItems< MemStoreMapExtraItem > MemStoreMapExtras
Definition: MemStore.h:22
Ipc::StoreMap MemStoreMap
Definition: MemStore.h:23
Shared memory page identifier, address, or handler.
Definition: Page.h:24
API for adjusting external state when dirty map slice is being freed.
Definition: StoreMap.h:398
Aggregates information required for updating entry metadata and headers.
Definition: StoreMap.h:182
temporary storage for slot and page ID pointers; for the waiting cache
Definition: MemStore.h:110
Ipc::Mem::PageId * slot
local slot variable, waiting to be filled
Definition: MemStore.h:114
Ipc::Mem::PageId * page
local page variable, waiting to be filled
Definition: MemStore.h:115
bool operator!() const
Definition: MemStore.h:113
virtual bool updateAnchored(StoreEntry &) override
Definition: MemStore.cc:410
void anchorEntry(StoreEntry &e, const sfileno index, const Ipc::StoreMapAnchor &anchor)
anchors StoreEntry to an already locked map entry
Definition: MemStore.cc:433
virtual void updateHeaders(StoreEntry *e) override
make stored metadata and HTTP headers the same as in the given entry
Definition: MemStore.cc:333
sfileno lastWritingSlice
the last allocate slice for writing a store entry (during copyToShm)
Definition: MemStore.h:106
virtual uint64_t currentCount() const override
the total number of objects stored right now
Definition: MemStore.cc:277
Ipc::Mem::Pointer< Extras > extras
IDs of pages with slice data.
Definition: MemStore.h:103
Ipc::Mem::PageId pageForSlice(Ipc::StoreMapSliceId sliceId)
safely returns a previously allocated memory page for the given entry slice
Definition: MemStore.cc:752
bool updateAnchoredWith(StoreEntry &, const sfileno, const Ipc::StoreMapAnchor &)
updates Transients entry after its anchor has been located
Definition: MemStore.cc:424
void copyToShmSlice(StoreEntry &e, Ipc::StoreMapAnchor &anchor, Ipc::StoreMap::Slice &slice)
copies at most one slice worth of local memory to shared memory
Definition: MemStore.cc:685
void disconnect(StoreEntry &e)
called when the entry is about to forget its association with mem cache
Definition: MemStore.cc:907
virtual uint64_t minSize() const override
the minimum size the store will shrink to via normal housekeeping
Definition: MemStore.cc:258
bool shouldCache(StoreEntry &e) const
whether we should cache the entry
Definition: MemStore.cc:572
MemStore()
Definition: MemStore.cc:161
virtual ~MemStore()
Definition: MemStore.cc:165
virtual void evictCached(StoreEntry &) override
Definition: MemStore.cc:881
virtual void create() override
create system resources needed for this store to operate in the future
Definition: MemStore.h:48
Ipc::Mem::Pointer< Ipc::Mem::PageStack > freeSlots
unused map slot IDs
Definition: MemStore.h:99
SlotAndPage waitingFor
a cache for a single "hot" free slot and page
Definition: MemStore.h:117
void completeWriting(StoreEntry &e)
all data has been received; there will be no more write() calls
Definition: MemStore.cc:863
virtual void stat(StoreEntry &e) const override
Definition: MemStore.cc:215
MemStoreMapExtras Extras
Definition: MemStore.h:102
virtual uint64_t maxSize() const override
Definition: MemStore.cc:264
bool keepInLocalMemory(const StoreEntry &e) const
whether e should be kept in local RAM for possible future caching
virtual StoreEntry * get(const cache_key *) override
Definition: MemStore.cc:301
void copyToShm(StoreEntry &e)
copies all local data to shared memory
Definition: MemStore.cc:649
virtual int64_t maxObjectSize() const override
the maximum size of a storable object; -1 if unlimited
Definition: MemStore.cc:283
Ipc::StoreMap::Slice & nextAppendableSlice(const sfileno entryIndex, sfileno &sliceOffset)
Definition: MemStore.cc:716
static int64_t EntryLimit()
calculates maximum number of entries we need to store and map
Definition: MemStore.cc:934
sfileno reserveSapForWriting(Ipc::Mem::PageId &page)
finds a slot and a free page to fill or throws
Definition: MemStore.cc:763
virtual void init() override
Definition: MemStore.cc:171
friend ShmWriter
Definition: MemStore.h:75
virtual void evictIfFound(const cache_key *) override
Definition: MemStore.cc:900
virtual void reference(StoreEntry &e) override
somebody needs this entry (many cache replacement policies need to know)
Definition: MemStore.cc:289
static bool Enabled()
whether Squid is correctly configured to use a shared memory cache
Definition: MemStore.h:68
void updateHeadersOrThrow(Ipc::StoreMapUpdate &update)
Definition: MemStore.cc:353
static bool Requested()
Definition: MemStore.cc:927
virtual bool anchorToCache(StoreEntry &e, bool &inSync) override
Definition: MemStore.cc:393
bool copyFromShm(StoreEntry &e, const sfileno index, const Ipc::StoreMapAnchor &anchor)
copies the entire entry from shared to local memory
Definition: MemStore.cc:458
virtual bool dereference(StoreEntry &e) override
Definition: MemStore.cc:294
void write(StoreEntry &e)
copy non-shared entry data of the being-cached entry to our cache
Definition: MemStore.cc:824
bool copyFromShmSlice(StoreEntry &e, const StoreIOBuffer &buf, bool eof)
imports one shared memory slice into local memory
Definition: MemStore.cc:535
virtual uint64_t currentSize() const override
current size
Definition: MemStore.cc:270
virtual void maintain() override
perform regular periodic maintenance; TODO: move to UFSSwapDir::Maintain
Definition: MemStore.cc:253
bool startCaching(StoreEntry &e)
locks map anchor and preps to store the entry in shared memory
Definition: MemStore.cc:626
virtual void noteFreeMapSlice(const Ipc::StoreMapSliceId sliceId) override
adjust slice-linked state before a locked Readable slice is erased
Definition: MemStore.cc:802
MemStoreMap * map
index of mem-cached entries
Definition: MemStore.h:100
virtual void getStats(StoreInfoStats &stats) const override
collect statistics
Definition: MemStore.cc:202
High-level store statistics used by mgr:info action. Used inside PODs!
Definition: StoreStats.h:14
int32_t StoreMapSliceId
Definition: StoreMap.h:24
class Ping::pingStats_ stats
unsigned char cache_key
Store key.
Definition: forward.h:29
signed_int32_t sfileno
Definition: forward.h:22
Ipc::Mem::PageId page
shared memory page with entry slice content
Definition: MemStore.h:20

 

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