diff options
Diffstat (limited to 'mm')
| -rw-r--r-- | mm/filemap.c | 10 | ||||
| -rw-r--r-- | mm/readahead.c | 97 |
2 files changed, 64 insertions, 43 deletions
diff --git a/mm/filemap.c b/mm/filemap.c index 5eb0a6b9d60..49a6fe375d0 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -894,15 +894,15 @@ void do_generic_mapping_read(struct address_space *mapping, find_page: page = find_get_page(mapping, index); if (!page) { - page_cache_readahead_ondemand(mapping, - &ra, filp, page, + page_cache_sync_readahead(mapping, + &ra, filp, index, last_index - index); page = find_get_page(mapping, index); if (unlikely(page == NULL)) goto no_cached_page; } if (PageReadahead(page)) { - page_cache_readahead_ondemand(mapping, + page_cache_async_readahead(mapping, &ra, filp, page, index, last_index - index); } @@ -1348,14 +1348,14 @@ retry_find: */ if (VM_SequentialReadHint(vma)) { if (!page) { - page_cache_readahead_ondemand(mapping, ra, file, page, + page_cache_sync_readahead(mapping, ra, file, vmf->pgoff, 1); page = find_lock_page(mapping, vmf->pgoff); if (!page) goto no_cached_page; } if (PageReadahead(page)) { - page_cache_readahead_ondemand(mapping, ra, file, page, + page_cache_async_readahead(mapping, ra, file, page, vmf->pgoff, 1); } } diff --git a/mm/readahead.c b/mm/readahead.c index 205a4a43151..3d262bb738a 100644 --- a/mm/readahead.c +++ b/mm/readahead.c @@ -359,7 +359,7 @@ static unsigned long get_next_ra_size(struct file_ra_state *ra, static unsigned long ondemand_readahead(struct address_space *mapping, struct file_ra_state *ra, struct file *filp, - struct page *page, pgoff_t offset, + bool hit_readahead_marker, pgoff_t offset, unsigned long req_size) { unsigned long max; /* max readahead pages */ @@ -387,7 +387,7 @@ ondemand_readahead(struct address_space *mapping, * Standalone, small read. * Read as is, and do not pollute the readahead state. */ - if (!page && !sequential) { + if (!hit_readahead_marker && !sequential) { return __do_page_cache_readahead(mapping, filp, offset, req_size, 0); } @@ -408,7 +408,7 @@ ondemand_readahead(struct address_space *mapping, * E.g. interleaved reads. * Not knowing its readahead pos/size, bet on the minimal possible one. */ - if (page) { + if (hit_readahead_marker) { ra_index++; ra_size = min(4 * ra_size, max); } @@ -421,50 +421,71 @@ fill_ra: } /** - * page_cache_readahead_ondemand - generic file readahead + * page_cache_sync_readahead - generic file readahead * @mapping: address_space which holds the pagecache and I/O vectors * @ra: file_ra_state which holds the readahead state * @filp: passed on to ->readpage() and ->readpages() - * @page: the page at @offset, or NULL if non-present - * @offset: start offset into @mapping, in PAGE_CACHE_SIZE units + * @offset: start offset into @mapping, in pagecache page-sized units * @req_size: hint: total size of the read which the caller is performing in - * PAGE_CACHE_SIZE units + * pagecache pages * - * page_cache_readahead_ondemand() is the entry point of readahead logic. - * This function should be called when it is time to perform readahead: - * 1) @page == NULL - * A cache miss happened, time for synchronous readahead. - * 2) @page != NULL && PageReadahead(@page) - * A look-ahead hit occured, time for asynchronous readahead. + * page_cache_sync_readahead() should be called when a cache miss happened: + * it will submit the read. The readahead logic may decide to piggyback more + * pages onto the read request if access patterns suggest it will improve + * performance. */ -unsigned long -page_cache_readahead_ondemand(struct address_space *mapping, - struct file_ra_state *ra, struct file *filp, - struct page *page, pgoff_t offset, - unsigned long req_size) +void page_cache_sync_readahead(struct address_space *mapping, + struct file_ra_state *ra, struct file *filp, + pgoff_t offset, unsigned long req_size) { /* no read-ahead */ if (!ra->ra_pages) - return 0; - - if (page) { - /* - * It can be PG_reclaim. - */ - if (PageWriteback(page)) - return 0; - - ClearPageReadahead(page); - - /* - * Defer asynchronous read-ahead on IO congestion. - */ - if (bdi_read_congested(mapping->backing_dev_info)) - return 0; - } + return; + + /* do read-ahead */ + ondemand_readahead(mapping, ra, filp, false, offset, req_size); +} +EXPORT_SYMBOL_GPL(page_cache_sync_readahead); + +/** + * page_cache_async_readahead - file readahead for marked pages + * @mapping: address_space which holds the pagecache and I/O vectors + * @ra: file_ra_state which holds the readahead state + * @filp: passed on to ->readpage() and ->readpages() + * @page: the page at @offset which has the PG_readahead flag set + * @offset: start offset into @mapping, in pagecache page-sized units + * @req_size: hint: total size of the read which the caller is performing in + * pagecache pages + * + * page_cache_async_ondemand() should be called when a page is used which + * has the PG_readahead flag: this is a marker to suggest that the application + * has used up enough of the readahead window that we should start pulling in + * more pages. */ +void +page_cache_async_readahead(struct address_space *mapping, + struct file_ra_state *ra, struct file *filp, + struct page *page, pgoff_t offset, + unsigned long req_size) +{ + /* no read-ahead */ + if (!ra->ra_pages) + return; + + /* + * Same bit is used for PG_readahead and PG_reclaim. + */ + if (PageWriteback(page)) + return; + + ClearPageReadahead(page); + + /* + * Defer asynchronous read-ahead on IO congestion. + */ + if (bdi_read_congested(mapping->backing_dev_info)) + return; /* do read-ahead */ - return ondemand_readahead(mapping, ra, filp, page, - offset, req_size); + ondemand_readahead(mapping, ra, filp, true, offset, req_size); } -EXPORT_SYMBOL_GPL(page_cache_readahead_ondemand); +EXPORT_SYMBOL_GPL(page_cache_async_readahead); |