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Diffstat (limited to 'innobase/include/buf0rea.h')
| -rw-r--r-- | innobase/include/buf0rea.h | 98 |
1 files changed, 98 insertions, 0 deletions
diff --git a/innobase/include/buf0rea.h b/innobase/include/buf0rea.h new file mode 100644 index 00000000000..1efe67369ab --- /dev/null +++ b/innobase/include/buf0rea.h @@ -0,0 +1,98 @@ +/****************************************************** +The database buffer read + +(c) 1995 Innobase Oy + +Created 11/5/1995 Heikki Tuuri +*******************************************************/ + +#ifndef buf0rea_h +#define buf0rea_h + +#include "univ.i" +#include "buf0types.h" + +/************************************************************************ +High-level function which reads a page asynchronously from a file to the +buffer buf_pool if it is not already there. Sets the io_fix flag and sets +an exclusive lock on the buffer frame. The flag is cleared and the x-lock +released by the i/o-handler thread. Does a random read-ahead if it seems +sensible. */ + +ulint +buf_read_page( +/*==========*/ + /* out: number of page read requests issued: this can + be > 1 if read-ahead occurred */ + ulint space, /* in: space id */ + ulint offset);/* in: page number */ +/************************************************************************ +Applies linear read-ahead if in the buf_pool the page is a border page of +a linear read-ahead area and all the pages in the area have been accessed. +Does not read any page if the read-ahead mechanism is not activated. Note +that the the algorithm looks at the 'natural' adjacent successor and +predecessor of the page, which on the leaf level of a B-tree are the next +and previous page in the chain of leaves. To know these, the page specified +in (space, offset) must already be present in the buf_pool. Thus, the +natural way to use this function is to call it when a page in the buf_pool +is accessed the first time, calling this function just after it has been +bufferfixed. +NOTE 1: as this function looks at the natural predecessor and successor +fields on the page, what happens, if these are not initialized to any +sensible value? No problem, before applying read-ahead we check that the +area to read is within the span of the space, if not, read-ahead is not +applied. An uninitialized value may result in a useless read operation, but +only very improbably. +NOTE 2: the calling thread may own latches on pages: to avoid deadlocks this +function must be written such that it cannot end up waiting for these +latches! +NOTE 3: the calling thread must want access to the page given: this rule is +set to prevent unintended read-aheads performed by ibuf routines, a situation +which could result in a deadlock if the OS does not support asynchronous io. */ + +ulint +buf_read_ahead_linear( +/*==================*/ + /* out: number of page read requests issued */ + ulint space, /* in: space id */ + ulint offset);/* in: page number of a page; NOTE: the current thread + must want access to this page (see NOTE 3 above) */ +/************************************************************************ +Issues read requests for pages which the ibuf module wants to read in, in +order to contract insert buffer trees. Technically, this function is like +a read-ahead function. */ + +void +buf_read_ibuf_merge_pages( +/*======================*/ + ibool sync, /* in: TRUE if the caller wants this function + to wait for the highest address page to get + read in, before this function returns */ + ulint space, /* in: space id */ + ulint* page_nos, /* in: array of page numbers to read, with + the highest page number last in the array */ + ulint n_stored); /* in: number of page numbers in the array */ +/************************************************************************ +Issues read requests for pages which recovery wants to read in. */ + +void +buf_read_recv_pages( +/*================*/ + ibool sync, /* in: TRUE if the caller wants this function + to wait for the highest address page to get + read in, before this function returns */ + ulint space, /* in: space id */ + ulint* page_nos, /* in: array of page numbers to read, with the + highest page number the last in the array */ + ulint n_stored); /* in: number of page numbers in the array */ + +/* The size in pages of the area which the read-ahead algorithms read if +invoked */ + +#define BUF_READ_AHEAD_AREA ut_min(32, buf_pool->curr_size / 16) + +/* Modes used in read-ahead */ +#define BUF_READ_IBUF_PAGES_ONLY 131 +#define BUF_READ_ANY_PAGE 132 + +#endif |