foedus::cache::CacheBucket Struct Reference

Hash bucket in cache table. More...

Detailed Description

Hash bucket in cache table.

Every essential information in the hashtable is repsented in this 8-byte. Thus, all simple reads/writes are guaranteed to be complete and consistent (at least regular). This is one of the main tricks to make snapshot cache wait-free.

Higher 32 bit is PageIdTag to efficiently check (with false positives) the bucket points to the page or not. Lower 32 bit is ContentId, or the offset in the page pool.

We always read-write these information as complete 64bit to allow regular-reads and atomic-writes. We never do atomic operations in this module thanks to the loose requirement in the snapshot cache.

But, just be careful on regular-reads and implicitly-atomic-writes. Compiler might do something surprising if we don't explicitly prohibit it. For this purpose, we use a macro equivalent to linux's ACCESS_ONCE. For more details, see: http://lwn.net/Articles/508991/

Definition at line 140 of file cache_hashtable.hpp.

#include <cache_hashtable.hpp>

Public Member Functions
void	reset (ContentId id=0, PageIdTag tag=0)
ContentId	get_content_id () const
void	set_content_id (ContentId id)
bool	is_content_set () const
PageIdTag	get_tag () const
void	set_tag (PageIdTag tag)
	same note as set_content_id() More...

Public Attributes
uint64_t	data_

Member Function Documentation

ContentId foedus::cache::CacheBucket::get_content_id ( ) const

inline

Definition at line 147 of file cache_hashtable.hpp.

References data_.

Referenced by foedus::cache::CacheHashtable::evict_overflow_loop(), foedus::cache::CacheHashtable::find(), foedus::cache::CacheHashtable::find_batch(), and is_content_set().

{ return data_; }

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PageIdTag foedus::cache::CacheBucket::get_tag ( ) const

inline

Definition at line 155 of file cache_hashtable.hpp.

Referenced by foedus::cache::CacheHashtable::find(), and foedus::cache::CacheHashtable::find_batch().

{ return static_cast<PageIdTag>(data_ >> 32); }

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bool foedus::cache::CacheBucket::is_content_set ( ) const

inline

Definition at line 153 of file cache_hashtable.hpp.

References get_content_id().

{ return get_content_id() != 0; }

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void foedus::cache::CacheBucket::reset ( ContentId  id = 0, PageIdTag  tag = 0  )

inline

Definition at line 143 of file cache_hashtable.hpp.

Referenced by foedus::cache::CacheHashtable::CacheHashtable(), and foedus::cache::CacheHashtable::install().

                                                     {
    data_ = (static_cast<uint64_t>(tag) << 32) | id;
  }

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void foedus::cache::CacheBucket::set_content_id ( ContentId  id )

inline

Note

this operation is not guaranteed to be either atomic or reglar. This should be called only in a local instance of this object, then copied to somewhere as a whole 64bit.

Definition at line 152 of file cache_hashtable.hpp.

{ data_ = (data_ & 0xFFFFFFFF00000000ULL) | id; }

void foedus::cache::CacheBucket::set_tag ( PageIdTag  tag )

inline

same note as set_content_id()

Definition at line 157 of file cache_hashtable.hpp.

                                   {
    data_ = (data_ & 0x00000000FFFFFFFFULL) | (static_cast<uint64_t>(tag) << 32);
  }

Member Data Documentation

uint64_t foedus::cache::CacheBucket::data_

Definition at line 141 of file cache_hashtable.hpp.

Referenced by foedus::cache::CacheHashtable::evict_main_loop(), foedus::cache::CacheHashtable::evict_overflow_loop(), and get_content_id().

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The documentation for this struct was generated from the following file:

• /home/shino/foedus_code/foedus-core/include/foedus/cache/cache_hashtable.hpp