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The linear read-ahead (enabled by nonzero innodb_read_ahead_threshold) works best if index leaf pages or undo log pages have been allocated on adjacent page numbers. The read-ahead is assumed not to be helpful in other types of page accesses, such as non-leaf index pages. buf_page_get_low(): Do not invoke buf_page_t::set_accessed(), buf_page_make_young_if_needed(), or buf_read_ahead_linear(). We will invoke them in those callers of buf_page_get_gen() or buf_page_get() where it makes sense: the access is not one-time-on-startup and the page and not going to be freed soon. btr_copy_blob_prefix(), btr_pcur_move_to_next_page(), trx_undo_get_prev_rec_from_prev_page(), trx_undo_get_first_rec(), btr_cur_t::search_leaf(), btr_cur_t::open_leaf(): Invoke buf_read_ahead_linear(). We will not invoke linear read-ahead in functions that would essentially allocate or free pages, because pages that are freshly allocated are expected to be initialized by buf_page_create() and not read from the data file. Likewise, freeing pages should not involve accessing any sibling pages, except for freeing singly-linked lists of BLOB pages. We will not invoke read-ahead in btr_cur_t::pessimistic_search_leaf() or in a pessimistic operation of btr_cur_t::open_leaf(), because it is assumed that pessimistic operations should be preceded by optimistic operations, which should already have invoked read-ahead. buf_page_make_young_if_needed(): Invoke also buf_page_t::set_accessed() and return the result. btr_cur_nonleaf_make_young(): Like buf_page_make_young_if_needed(), but do not invoke buf_page_t::set_accessed(). Reviewed by: Vladislav Lesin Tested by: Matthias Leich |
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| .. | ||
| buf0block_hint.cc | ||
| buf0buddy.cc | ||
| buf0buf.cc | ||
| buf0checksum.cc | ||
| buf0dblwr.cc | ||
| buf0dump.cc | ||
| buf0flu.cc | ||
| buf0lru.cc | ||
| buf0rea.cc | ||