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[t:3643], add comments describing the cachetable callbacks

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git-svn-id: file:///svn/toku/tokudb@32909 c7de825b-a66e-492c-adef-691d508d4ae1
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Zardosht Kasheff 2013-04-16 23:59:44 -04:00 • committed by Yoni Fogel
parent 108a698022
commit 3c639c71e6
1 changed files with 11 additions and 2 deletions
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13
newbrt/cachetable.h
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@ -123,6 +123,12 @@ typedef void (*CACHETABLE_FLUSH_CALLBACK)(CACHEFILE, int fd, CACHEKEY key, void
// Can access fd (fd is protected by a readlock during call)
typedef int (*CACHETABLE_FETCH_CALLBACK)(CACHEFILE, int fd, CACHEKEY key, u_int32_t fullhash, void **value, long *sizep, int *dirtyp, void *read_extraargs);
// The partial eviction callback is called by the cachetable to possibly try and partially evict pieces
// of the PAIR. The strategy for what to evict is left to the callback. The callback may choose to free
// nothing, may choose to free as much as possible.
// bytes_to_free is the number of bytes the cachetable wants freed.
// bytes_freed is returned by the callback telling the cachetable how much space was freed
// Requires a write lock to be held on the PAIR in the cachetable while this function is called
typedef int (*CACHETABLE_PARTIAL_EVICTION_CALLBACK)(void *brtnode_pv, long bytes_to_free, long* bytes_freed, void *write_extraargs);
// This callback is called by the cachetable to ask if a partial fetch is required of brtnode_pv. If a partial fetch
@ -130,11 +136,14 @@ typedef int (*CACHETABLE_PARTIAL_EVICTION_CALLBACK)(void *brtnode_pv, long bytes
// this callback exists instead of just doing the same functionality in CACHETABLE_PARTIAL_FETCH_CALLBACK
// is so that we can call this cheap function with the ydb lock held, in the hopes of avoiding the more expensive sequence
// of releasing the ydb lock, calling the partial_fetch_callback, reading nothing, reacquiring the ydb lock
// Requires: a read lock to be held on the PAIR
typedef BOOL (*CACHETABLE_PARTIAL_FETCH_REQUIRED_CALLBACK)(void *brtnode_pv, void *read_extraargs);
// The partial fetch callback is called when a thread needs to read a subset of a PAIR into memory
// The partial fetch callback is called when a thread needs to read a subset of a PAIR into memory.
// An example would be needing to read a basement node into memory. In that case,
// Requires a write lock to be held on the PAIR in the cachetable while this function is called
// The new size of the PAIR is returned in sizep
// Returns: 0 if success, otherwise an error number.
// The number of bytes added is returned in sizep
typedef int (*CACHETABLE_PARTIAL_FETCH_CALLBACK)(void *brtnode_pv, void *read_extraargs, int fd, long *sizep);
void toku_cachefile_set_userdata(CACHEFILE cf, void *userdata,